River.Space.Design by Birkhäuser

Adding bed load ∆ Agriculture ∆ Art objects and furniture ∆ Attachable protection elements ∆ Backwaters ∆ Balconies ∆ Bank reinforcement as needed ∆ Bioengineered groynes ∆ Boulders and stepping stones ∆ Branches ∆ Broad riverbank steps ∆ Building over the existing reinforcement ∆ Buildings on piles ∆ Cableways ∆ Camping and caravan sites ∆ Closable access ∆ Creating meanders ∆ Creating multiple channels ∆ Creating scour holes ∆ Dead wood ∆ Dike parks ∆ Dike steps and promenades ∆ Dikes as path networks ∆ Electronic warning systems ∆ Escape routes ∆ Events grounds ∆ Extending the flow length ∆ Extensive natural areas ∆ Fish passes ∆ Floating and amphibious houses ∆ Floating islands ∆ Floating jetties ∆ Flood channels ∆ Flood-tolerant buildings ∆ Fold-out protection elements ∆ Foreshores ∆ Glass walls ∆ High water marks ∆ Incorporating a straightened channel ∆ Influencing perceptions of the wall height ∆ Integrating flood protection walls ∆ Intermediate levels ∆ Introducing disruptive elements ∆ Invisible stabilisation ∆ Laid stone groynes ∆ Large single rocks ∆ Living revetment ∆ Marinas ∆ Masonry riverbank revetment ∆ Moored ships ∆ Mound principle with buildings ∆ Mounds ∆ New embankment walls ∆ Overhangs ∆ Parks within the flood plain ∆ Partially naturalising the riverbank ∆ Paths within the flood plain ∆ Piled stone groynes ∆ Polder systems ∆ Portable protection elements ∆ Ramps and slides ∆ Regulating water extraction ∆ Removing riverbank and riverbed reinforcement ∆ Reprofiling the channel cross-section ∆ Reprofiling the dike section ∆ Reprofiling the flood plain ∆ Retaining sightlines ∆ Retention basins ∆ River access parallel to the bank ∆ River access perpendicular to the bank ∆ Riverbed sills ∆ Sand and gravel beaches in bays ∆ Sand and gravel beaches on inner bends ∆ Selective bank reinforcement ∆ Semi-natural riparian management ∆ Setting back the dike ∆ ‘Sleeping’ riverbank reinforcement ∆ Sports facilities and playgrounds ∆ Stone revetment ∆ Submerged groynes ∆ Submergible boardwalks ∆ Submergible furniture ∆ Submergible planting ∆ Submergible riverside paths ∆ Superdikes ∆ Surmounting the embankment wall ∆ Suspended pathways ∆ Terraced stone revetment ∆ Terraces ∆ Trees on dikes ∆ Underwater steps ∆ Using the historical city wall ∆ Varying the riverbed and transverse structures ∆ Warning signs and barriers ∆ Watertight facades ∆ Widening the channel

River. Space. Design.

River. Space. Design is a systematically organised reference book for the design and planning of river spaces. Urban river landscapes need to unite a broad range of requirements – most notably flood control, ecological considerations and open space design – often within tight space constraints. Taking a processoriented approach, this book offers concrete guidelines for sustainable longterm interventions. Arranged in two volumes, this book contains a comparative analysis of more than 50 successful projects alongside rivers and streams in Europe, and dissects them into their individual design elements. The result is a catalogue of effective design strategies and tools that provides readers with an attractive and inspiring overview of the broad and varied spectrum of design possibilities for river spaces. Each project is illustrated with photographs taken especially for the book and each principle is illustrated with explanatory diagrams. The book’s interdisciplinary structure is of interest to landscape architects, architects, engineers, urban planners and hydrologists alike.

River. Space. Design. Planning Strategies, Methods and Projects for Urban Rivers Martin Prominski Antje Stokman Susanne Zeller Daniel Stimberg Hinnerk Voermanek

∂

Foreword ∫ 5 Herbert Dreiseitl

Fundamentals

Design Catalogue Introduction ∫ 38

Introduction ∫ 8

Process spaces ∫ 39 List of process spaces and design strategies ∫ 42 List of design tools and design measures ∫ 44

Objectives ∫ 9 Selection of projects ∫ ∂∂ The book’s structure ∫ ∂2

Process Space A Embankment Walls and Promenades ∫ 46

Multifunctionality ∫ ∂5 Interdisciplinarity ∫ ∂6 Process orientation ∫ ∂7

A1 Linear spatial expansion ∫ 52 A2 Selective spatial expansion ∫ 54 A3 Temporary resistance ∫ 56 A4 Placing over the water ∫ 58 A5 Tolerating ∫ 60 A6 Adapting ∫ 64

Water Spaces and their Processes ∫ ∂8

Process Space B Dikes and Flood Walls ∫ 66

Processes and their driving forces ∫ ∂9 Types of processes ∫ 20 Water landscapes as an expression of spatiotemporal processes ∫ 25

B1 Differentiating resistance ∫ 72 B2 Vertical resistance ∫ 76 B3 Reinforcing resistance ∫ 78 B4 Integrating resistance ∫ 80 B5 Temporary resistance ∫ 82 B6 Making river dynamics evident ∫ 84

Prerequisites for Planning Urban River Spaces ∫ ∂4

Designing Water Spaces ∫ 28 Water spaces and their limits ∫ 29 Types of limits ∫ 31 Riparian landscapes between control and dynamism ∫ 33

Process Space C Flood Areas ∫ 86 C1 Extending the space ∫ 92 C2 Placing over the water ∫ 96 C3 Tolerating ∫ ∂00 C4 Evading ∫ ∂04 C5 Adapting ∫ ∂06

Process Space D Riverbeds and Currents ∫ ∂08 D1 Deflecting the current ∫ ∂∂4 D2 Grading the channel ∫ ∂∂8 D3 Varying the riverbed ∫ ∂20 D4 Varying the bank reinforcement ∫ ∂22 D5 Varying the riverbed reinforcement ∫ ∂26

Process Space E Dynamic River Landscapes ∫ ∂28 E1 Allowing channel migration ∫ ∂34 E2 Initiating channel dynamics ∫ ∂36 E3 Creating new channels ∫ ∂38 E4 Restricting channel dynamics ∫ ∂40

Project Catalogue Introduction ∆ ∂44 Map of projects ∆ ∂44

Process Space A Embankment Walls and Promenades ∆ ∂48 Elster and Pleiße Millraces, Leipzig, Germany ∆ ∂50 Leine, Hanover, Germany ∆ ∂54 Limmat, Zurich, Switzerland (Factory by the Water) ∆ ∂56 Limmat, Zurich, Switzerland (Wipkingerpark) ∆ ∂58 Rhône, Lyon, France ∆ ∂60 Seine, Choisy-le-Roi, France ∆ ∂64 Spree, Berlin, Germany ∆ ∂66 Wupper, Wuppertal, Germany ∆ ∂68

Process Space B Dikes and Flood Walls ∆ ∂70 IJssel, Doesburg, the Netherlands ∆ ∂72 IJssel, Kampen, the Netherlands ∆ ∂74 Main, Miltenberg, Germany ∆ ∂78 Main, Wörth am Main, Germany ∆ ∂80 Nahe, Bad Kreuznach, Germany ∆ ∂84 Waal, between Afferden and Dreumel, the Netherlands ∆ ∂88 Waal, Zaltbommel, the Netherlands ∆ ∂90

Process Space D Riverbeds and Currents ∆ 232 Ahna, Kassel, Germany ∆ 234 Alb, Karlsruhe, Germany ∆ 236 Birs, Basle, Switzerland ∆ 238 Leutschenbach, Zurich, Switzerland ∆ 240 Neckar, Ladenburg, Germany ∆ 242 Seille, Metz, France ∆ 246 Soestbach, Soest, Germany ∆ 248 Wiese, Basle, Switzerland ∆ 250 Wiese, Lörrach, Germany ∆ 252

Process Space E Dynamic River Landscapes ∆ 254 Emscher, Dortmund, Germany ∆ 256 Isar, Munich, Germany ∆ 260 Losse, Kassel, Germany ∆ 264 Schunter, Braunschweig, Germany ∆ 266 Wahlebach, Kassel, Germany ∆ 268 Werse, Beckum, Germany ∆ 270

Process Space C Flood Areas ∆ ∂92 Bergsche Maas, between Waalwijk and Geertruidenberg, the Netherlands ∆ ∂94 Besòs, Barcelona, Spain ∆ ∂96 Ebro, Zaragoza, Spain ∆ ∂98 Elbe, Hamburg, Germany ∆ 202 Gallego, Zuera, Spain ∆ 204 IJssel, Zwolle, the Netherlands ∆ 208 Kyll, Trier, Germany ∆ 2∂0 Maas, Maasbommel, the Netherlands ∆ 2∂2 Petite Gironde, Coulaines, France ∆ 2∂4 Rhine, Brühl, Germany ∆ 2∂8 Rhine, Mannheim, Germany ∆ 220 Seine, Le Pecq, France ∆ 222 Waal, Gameren, the Netherlands ∆ 224 Wantij, Dordrecht, the Netherlands ∆ 228 Wupper, Müngsten, Germany ∆ 230

Appendix Project Credits and References ∆ 273 Further Reference Projects ∆ 279 Glossary ∆ 282 Selected Bibliography ∆ 285 Indices ∆ 288 Authors ∆ 294 Acknowledgements ∆ 294 Illustration Credits ∆ 295

Is not every river quite extraordinary? Not one is identical in its morphology, limnology or atmosphere with another. Rivers, the veins of our landscape, are thrilling, living entities. One day a river can reflect the gentle dance of sunlight on the water; the next be a foaming torrent tearing at all that stands in its way and carrying it off. Rivers are far more than moving water â&#x20AC;&#x201C; this would be an inadmissible simplification. It is the inimitable interplay of a body of flowing water with its bed, the shaping of its banks and its surroundings, which makes each river an inimitable personality with its own character, recounted in legends, songs and stories since time immemorial and still familiar to us today. Nearly all our cities and urban cultural spaces grew up on riverbanks and their development and the prosperity of their inhabitants also tell a story of their relationship with the water; trade, transport and industry flourished because of the navigability of these rivers and their significance as transport routes. For centuries, rivers were an important source of food for people settled close to their banks. Water, and the shaping of water landscapes by human hand, are the foundation of our cultures. However, a river can be both blessing and curse! It is no coincidence that humanityâ&#x20AC;&#x2122;s first engineering constructions were to regulate rivers; their purpose was always to protect settlements from the raging destructive forces of floodwater. Conversely, it was the taming and regulation of watercourses that, in many places, made it at all possible for cultural landscapes to evolve. Nowadays our rivers are to a large extent built up, straightened, transformed into feats of engineering â&#x20AC;&#x201C; their original form and the way they shape the landscape are barely perceptible. However, it is not only since the catastrophic floods of recent years, the consequences of climate change and the decline of species diversity beside and in the water that the total control and one-sided technical perception of our straitjacketed rivers has been increasingly called into question. Both through the formulation and implementation of the EU Water Framework Directive, aiming to achieve a good condition of all European watercourses, and through steadily growing public awareness, rivers are increasingly prominent subjects of general attention. This is not solely a question of hydraulics and technical flood defences. The possibilities for recreational use are becoming more and more important as we rediscover our rivers as places for contemplation and recuperation. With considerable improvements in water quality through better wastewater treatment and rainwater management, an urban river is no longer the shunned stinking backwater of a city but its fairest face and first impression. And thus the aesthetics of a watercourse space, expressed in its morphology and the form of its banks, becomes ever more significant; the way we deal with a river is shifting from hard technical hydraulic engineering to semi-natural biological engineering for shaping watercourses as multifunctional places for all flora, fauna and people along and in the water. In accordance with contemporary expectations, we want rivers in good condition and well-designed that, as living organisms, are also a fount of vitality for city dwellers. How are such aims to be achieved, what examples are worthy of emulation, and what are the deciding factors of practical implementation? These are, today, the burning questions in watercourse design and water space revitalisation. It is for precisely these reasons that the appearance of such a book as River.Space. Design is long overdue. With its excellently prepared content, crystal-clear structure and methodology, this book is addressed to experts and interested laymen alike. For decision makers in politics and public administration the interdisciplinary connections are illuminated and planners, engineers and contractors will find valuable suggestions for their own work. Last not least, River.Space.Design is a rich source for everyone with a professional interest in water, a spring from which all may drink their fill! May we hope that our rivers retain, also in controlled form, the potency of their form and ancient power, to create and enliven a vital urban landscape for all town and city dwellers.

Foreword Herbert Dreiseitl

4 5

Foreword

Introduction Elbe, HafenCity Hamburg. Many cities are once again rediscovering their rivers. In these new waterside landscapes and waterfronts, responses to the multifarious demands of town planning, flood protection, ecology and amenity are interwoven in the most innovative ways.

Objectives Urban rivers and their environs have undergone a dramatic metamorphosis: having been long neglected, they are currently being developed into the most prestigious sites in town. This in its turn places a multitude of new requirements upon them, making their design disproportionately more demanding – urban riverscapes are to expected become attractive open spaces and a powerful locational factor in the economic competition between cities; the 2000 EU Water Framework Directive requires high ecological standards throughout, and at the same time urban development is exposed to extremes of weather and flooding as a consequence of climate change. All these requirements have to be met by urban watercourse systems – often within the most restricted of spaces.

Impetus for action from EU directives

Seen in water management terms, predictions of climate change and isolated flood and low-flow emergencies have directed attention to the necessity of adapting urban river spaces. The prognosis of longer periods of drought, more frequent heavy downpours and rising sea levels has led to the critical examination of flood protection systems and of cities’ water supply and wastewater systems. The 2007 EU Flood Risk Management Directive committed member states to carry out precise evaluations of the dangers posed by flooding and to draw up management plans to improve flood protection. The resulting necessary mitigation works are bringing change to the urban environment, both above and below ground. In parallel, the EU Water Framework Directive prioritises ecological objectives such as better water quality and watercourse structure: The Directive requires member states to ‘protect, enhance and restore all bodies of surface water’ [WFD, Article 4]. Extensive surveys of the status quo are now being followed by many projects to fulfil the Directive’s requirements. Professional associations for water management such as the Deutsche Vereinigung für Wasserwirtschaft, Abwasser und Abfall e.V. [DWA 2009] are also devising their own regulatory frameworks for the design and enhancement of watercourses in the urban environment, and calling for holistic approaches to reconcile the sometimes contradictory claims upon them. In recent years, water in the city has been attracting increasing attention from an urban planning point of view. Cities are clearly turning their faces back towards their rivers and lakes: waterside living and work environments, city beaches, port regeneration and new riverside promenades are being developed to improve the quality of urban life. Responding to the relevance of this issue, for some time now many projects to redevelop the urban riparian landscape – both the watercourse itself and its banks – have emerged and been implemented. Taken as a whole, the performance requirements for these watercourses are complex, and demand close collaboration between the various stakeholders: water management professionals, town planners, architects, landscape architects, nature conservationists and representatives of other fields. Because of the multifarious nature of urban rivers, every project quickly becomes an interdisciplinary challenge; above all the conflicting interests of safety and the search for a new closeness to water places tremendous demands on designers’ capabilities. Today, many successful redevelopment measures have been undertaken around the world and are documented in diverse professional journals, books and databases. For those now faced with designing an urban river space, knowledge of good reference projects is important, but the search is laborious and time-consuming and the results tend to be unsatisfactory because each case study is too specific to be applicable to one’s own planning task. What has been lacking up to date is an overview that presents the wide diversity of design possibilities for urban river spaces in a systematic and transferable way. This book aims to fill this gap and serve as a primer and reference for designers of urban river spaces, and pursues the following primary objectives: 1. Create transferable knowledge From the built designs for urban river spaces that are exemplary for various reasons, the design tools were abstracted and sorted by typology. A catalogue of design strategies derived from this makes it easier for practitioners to

8 9

Fundamentals Introduction

transfer content to their own design tasks. Graphically clear presentations facilitate fast comprehension of the strategies and design tools and their spatial relevance. 2. Find an interdisciplinary language The typological order that has been devised integrates key aspects from all disciplines involved in the design of urban river spaces. This interdisciplinary presentation method and language promotes collaborative project work between landscape architects, ecologists, architects and urban planners – something of the utmost importance in the light of the complexity of designing urban river spaces. 3. Describe the processes of watercourses Rivers are constantly in motion – to say this is to make the obvious point that river spaces are subject to continuous transformation through the various water processes. Process orientation is therefore indispensable when designing river spaces, and should be reflected in the way a design is presented. Many presentations of designs for river spaces, however, concentrate on just one state or situation and thus fall short of their potential. To enable the principles of processual scenarios within watercourse systems to be understood, visual presentation forms and vivid descriptions of the water-related processes have been devised for this book. 4. Establish connections between ecology, flood protection and amenity The significance of process-oriented design for the three major thematic fields of river design in urban space – ecology, flood protection, and amenity – is made plain. Possible synergies (but also conflicts) between these three thematic foci in spatial design are revealed. The interdisciplinary composition of the team of authors, comprised of landscape architects and hydraulic engineers, made it possible to examine the projects selected for the book from various points of view. Interviews with local experts, literature research and the team’s own analyses were abstracted into design strategies, and a systematics of design tools and measures was devised. The basis of this systemisation was an analysis of watercourse processes, an understanding of which forms the basis for a conceptional categorisation and description of the various design possibilities.

D∂.3 Laid stone groynes

Two examples of transferable design tools from the projects examined: as part of the restoration of the River Birs in Basle, stone groynes were set across the current; in Wörth on the River Main spectacular folding floodgates were integrated in the old city wall when it was adapted as the flood protection barrier.

Selection of projects Preparation for this book began with selecting examples of good practice which fulfilled predefined criteria. The selected projects address at least two of the three objectives – ecology, flood protection, and amenity; and the projects pursue an integrative approach that combines at least two of the above mentioned requirements in the sense of multiple coding so that the restricted urban space is used in different ways and public funds can be effectively employed. Projects that pursue a single objective have been included only in exceptional cases. Projects with differing intentions and characters were deliberately juxtaposed. Ecological, hydraulic or architectural objectives may have provided the initial impulse for the project. Correspondingly, the composition of the editorial team and the design languages of the projects are diverse. Contrasting the various projects, especially according to the way they addressed river processes, engenders new interdisciplinary insights and synergies. Secondly, each project demonstrates a conscious design attempt to deal with river dynamics. The spectrum ranges from the smallest interventions in a riverside promenade to large-scale processes of altering the riverbed. Thirdly, at least one particularly innovative design tool should be present; each project addresses an aspect that distinguishes it from other projects, or exemplifies a specific aspect not found in other projects. The overall design quality and uniqueness of the projects were not the primary selection criteria. The rivers in the various reference projects are very diverse. Consequently, not all the design tools or measures are transferable to all other projects.

B5.3 Fold-out protection elements

∂0 ∂∂

Fundamentals Introduction

The book’s structure The book is divided into two volumes: The first, left-hand volume begins with a fundamental description of the essentials of high-quality design of urban river spaces and the various process typologies that shape rivers, their appearance and their transformations (Part 1, Fundamentals). These fundamentals lay the theoretical foundation for the heart of the book – a catalogue of systematically organised design strategies with their respective design tools and measures. The catalogue is divided into five different ‘Process Spaces’ (A to E) in which the water processes in the defined spatial area of the river are variously shaped by design measures (Part 2, Design Catalogue) The second, right-hand volume (Part 3, Project Catalogue) contains the projects researched as examples of best practice from which the design tools are derived. These references are fully described with illustrations and plans, and the contexts in which they came into being. The projects are grouped under the five Process Spaces, and then ordered alphabetically by the name of the river. Additionally, the appendix to the second volume contains an extensive specialist glossary and an overview of all projects, their design strategies and tools.

Initiating channel dynamics

∫

All design tools in E2 can be combined with

–––––––– C∂.4 Reprofiling the flood plain C3.5 Extensive natural areas E∂.∂ Removing riverbank and riverbed reinforcement E∂.2 Semi-natural riparian management E3.∂ Creating meanders E3.2 Incorporating a straightened channel E3.3 Creating multiple channels E4.∂ ‘Sleeping’ riverbank reinforcement E4.2 Bank reinforcement as needed E4.3 Selective bank reinforcement

Selective interventions in the river, in the form of specific shifting of substrate along the banks or on the riverbed, stimulate morphodynamic processes. This strategy is applied when the desired effect of channel development out of the river’s inherent dynamic would come about only after a very long time. Its aim is to optimise the framework conditions for the inherent dynamics to create a structurally rich watercourse more quickly. These redeployments, then, serve merely to prime a strong internal dynamic under which the initial condition of the river will quickly disappear. Within a short period, varied habitats can arise that facilitate speedy colonisation by flora and fauna. At the same time the appearance of the river can also alter quickly, making it easier to communicate the intervention to the public although the actual course of the river channel is not changed at first. Most design tools to introduce morphodynamic processes exert an influence on the currents in the river, setting erosion and sedimentation processes in motion through their specific variation. Broadening the river at certain points slows down the flow and thus creates aggradations, while disruptive elements placed in the current can deflect it towards one bank and initiate erosion. As design leitmotif, it is possible to strive for a semi-natural appearance, for instance by using dead wood, or conversely to make the deflection of the current obvious by using plainly artificial elements. Introducing disruptive elements also means expanding habitat diversity, and stepping stones can facilitate direct contact with the water. A further option is to influence the framework conditions for the discharge and sediment transport processes. Direct mechanical deposition of sediment on the riverbed makes it easier for sand- and gravel banks or natural beaches to arise, while stimulating the discharge dynamics reinforces the operative forces and thus accelerates developments.

E2.∂

E2.2

E2.3

Reproﬁling the channel cross-section

Introducing disruptive elements

Adding bed load

Isar, Munich

Schunter, Braunschweig

Isar, Munich

Excavating the flood plain and flattening out the banks makes it possible for the river to develop beyond the former riverbank line. Selective excavations or shifting substrate within the riverbed creates sinks or shallow water zones; varying the crosssection raises the flow variation and a low water channel is created in the fasterflowing areas which serves to sustain the continuity of flow even during an extreme drought. Depending on the speed of the current, sediments of various particle sizes settle on the riverbed, as on the Isar in Munich, ranging from sand through gravel to larger stones – thus further enhancing the river’s structural diversity.

Disruptive elements are set at specifically chosen places in the riverbed to deflect the current towards the bank and catalyse erosion processes, or to encourage sedimentation on their sheltered downstream side. Disruptive elements can be just as well attached to the bank as placed in midstream. On the Schunter in Braunschweig fixed dead wood is used to divert the current and thus erode the opposite riverbank and create a steep slope. The disruptive elements enhance structural diversity and provide places to play and linger by on the waterside.

Many urban rivers lack natural sedimentation. Weirs or other cross-stream structures hinder the movement of bed load and the rivers suffer from sediment deficit. Deliberate deposition of sediments typical for the river provides material for riverbed enhancement. On the Isar in Munich, artificial sand or gravel banks were dumped, to be carried further downstream by the next high water event. If the lack of bed load is caused by weirs and ground sills, single openings in the structure can let the bed load overcome the barriers and contribute to the development of the next stretch of river.

–––––––– Isar, Munich ∆ 260

––––––––

Losse, Kassel ∆ 264

Isar, Munich ∆ 260

Emscher, Dortmund ∆ 256

Schunter, Braunschweig ∆ 266

Isar, Munich ∆ 260

Werse, Beckum ∆ 270

Wahlebach, Kassel ∆ 268 Werse, Beckum ∆ 270

∂36 ∂37

Design Catalogue Dynamic River Landscapes

The design tools and strategies in the first volume, and the project examples in the second volume, are cross-referenced.

N N

Connections

The two volumes are cross-referenced to be used in parallel. Several ways of reading the book are possible: in one direction, the abstracted design strategies in the left-hand volume can be put into tangible context by referring to the project examples in the right-hand volume, as all the design tools are linked by references to those projects that apply them. In the other direction, the projects in the right-hand volume make reference to the design tools in the left-hand volume. When the readers’ attention is caught by a tangible element of a project they can follow the reference to more closely examine the respective design tool and thus ascertain whether this element is transferable to their own project. The references are in the form of small arrows at the foot or the side of the page. An arrow to the left ∫ refers to the first, left-hand volume, an arrow to the right ∆ to the second, right-hand volume. This linking structure makes it possible to approach the book in several different ways; any of the three parts – Fundamentals (1), Design Catalogue (2) or Project Catalogue (3) – is an appropriate starting point.

A wild river with dynamic boundaries

Design tools

–––––––– B3.∂ Invisible stabilisation C∂.4 Reprofiling the flood plain D∂.2 Dead wood D5.∂ Fish passes E∂.∂ Removing riverbank and riverbed reinforcement E∂.3 Regulating water extraction E2.∂ Reprofiling the channel cross-section E2.2 Introducing disruptive elements E2.3 Adding bed load E3.3 Creating multiple channels E4.∂ ‘Sleeping‘ riverbank reinforcement

260 26∂

As early as the middle of the 19th century the Isar was canalised and straightened. The ‘torrential water’, as the Celts called the river, was steadily altered as its riverbanks were reinforced, its forelands closely mown, and the flow rate restricted with low weirs, thus preventing fish from migrating and sediment from being transported. In addition, in the south of Munich nearly all of the water in the river was diverted into a parallel canal in order to generate electricity. Only about 5 m3/s continued to flow within the tight profile, little more than a rivulet. As negotiations about the establishment of a new residual flow in this section of the river began, a discussion about the conversion of the Isar was also set in motion. Today 15 m3/s flow through the actual riverbed. The Isar is a gravel-dominated river in the alpine foothills prone to violent and sometimes sudden floods. The project area of the so-called Isar-Plan begins upstream of the city proper and stretches over 8 km to the centrally located Museum Island. The plan is a joint project of the City of Munich and the Free State of Bavaria, represented by the Munich Water Authority. The intent of the Isar-Plan is to increase contact with nature, improve flood management and offer more activities for rest and relaxation. Broadening the average width of the river from 50 m to up to 90 m was ecologically prudent and also increased the discharge cross-section. Due to this broadening, the height of the existing dikes did not have to be increased and the existing trees on them could be preserved. The dikes were stabilised, however, by adding an underground wall construction to their cores.

In terms of improving the quality of the river, the concept will promote the development of large-scale morphodynamic processes within clearly defined boundaries. In this way the river can, within specific limits, develop its own course within the flood plain. In order to restore some of the Isar’s original momentum, it was important to free the river of its canal-like corset: The trapezoidal profile made of stones and concrete was broken up and other protective measures removed. In order to protect the dikes ‘sleeping’ bank reinforcements were put in place, i.e., underground layers of stones that prevent the areas behind them from eroding. The river’s gravelly banks are subject to continuous change and are used by Munich’s residents as a large urban beach in the summer. It’s the perfect place for bathing, barbecuing, sunbathing and for ballgames. It’s also a perfect place for small children, who can splash around in the shallow water, for dogs, and even for people on horseback. The long gravel beach is only interrupted near the various bridges that cross the river. In these locations the riverbank needs to be sealed and the gravel is replaced by stone steps or walls. At the steps it’s possible to see just how much the river’s level fluctuates. The steps also create an interesting contrast to the wild gravel banks and are used as waterside seating areas.

1 Steps secure critical bottlenecks and make the entire riverbank usable [E4.3]. 2 Schematic section: The location of the ‘sleeping’ reinforcement is clearly visible [E4.∂]. Dikes were stabilised by using a concrete core [B3.1]. 3 In the redesigned sections ﬂat and constantly changing gravel beaches, like here at the Flaucher, have replaced steep grass-covered slopes. 4 Dead wood structures are held in place by foundations and initiate new processes of erosion and sedimentation. They are also very popular with playing children [D∂.2]. 5 The amount of water diverted into another branch of the river to produce energy has been reduced [E∂.3].

A learning process The ﬂoods in 2005 caused erosion damage beyond what had been planned for, and in doing so provided information about how the ﬂood management strategy should be adapted. As there is no planned or paved network of paths near the edge of the riverbank, a rough trail running directly on top of the ‘sleeping’ bank reinforcement was created, which has destroyed the protective grass cover. Barriers have now been put in place to prevent people from using the trail. In some places the ‘sleeping’ reinforcement has even been washed out. And while in some areas this condition has been allowed to persist, the river will continue to be carefully monitored. In this way, the conversion of the river can be seen as a learning process.

Project Catalogue Dynamic River Landscapes

∂2 ∂3

Fundamentals Introduction

Water Spaces and their Processes Historical map of the channel development of the Rivers Rhine and Neckar near Mannheim. The colours indicate how the river channels have shifted over time from the 6th century until 1850.

The word ‘process’ is derived from the Latin procedere, meaning ‘to advance, to proceed’; ‘process’ is a term for the directed course of an event – it is about movement, a dynamic, and an event that observes certain rules and regularities. ‘You could not step twice into the same river’ is Heraclitus’ famous dictum. This could also be understood to mean that water and processes can never be regarded as separate. The very currents and eddies of a river at any one moment show it to be a strongly dynamic element in the landscape, and observations over a longer period reveal that the entire river space exists in a constantly advancing, continuous process of change.

Rivers are dynamic

The entire scope of a river’s dynamic is hard to comprehend at first glance; nowadays it is to a large extent deliberately restricted and thereby mostly forgotten. Even so, the forces from which it is derived are ever-present and always potent. Mostly it is just the rise and fall of the water level which is clearly perceived by people, above all at times of extreme high or low water when changes are very noticeable. The extent to which bodies of water which are not subject to human influences are dynamic only becomes clear when observing the historical development of a watercourse over long periods. The constant shifting of the river’s course that can shape entire landscapes creates a complex, continually changing system – although the processes cover timescales that we cannot directly comprehend. The present course of a river is, seen in this light, no more than a snapshot in time of this ongoing process.

Processes and their driving forces The source of energy driving every dynamic process is the sun. It causes water to evaporate and the vapour rises to great heights where it condenses and turns into snow or rain. The potential energy stored in this way is transferred into kinetic energy when water falls as rain and flows down hills. The steeper the gradient, the more energy can be unleashed. In contact with the earth or rock, the kinetic energy of water can erode material and thus shape the terrain. The tractive force of flowing water carries the released material downstream; in principle, through erosion and sedimentation, rivers are continually wearing down higher-lying landscapes and raising the lower-lying river spaces. These processes are not constant and linear but occur in irregular phases: there are quieter and more dynamic phases but also sudden events such as cloudbursts and resulting flooding, through to natural disasters such as landslides or the avulsion of a loop in a river.

The energy that drives all the dynamic processes of a river and on which the natural water cycle is based is solar. When the energy-laden water meets the ground it creates a variety of river landscapes.

* * ** * * * * * ** * * * *

∂8 ∂9

Fundamentals Water Processes

system and also at every point within a river system, depending on the extent and characteristics of the catchment area and the local climate. Heavily built-up or steep catchment areas lead to more extreme discharge peaks in the river. Heavy rain causes high water conditions that flow downstream in a wave from the rainfall location. Sub-process 1: vertical water level fluctuations The discharge and resultant level of a river changes almost daily, although mostly it is only extreme high or low water events that are noticed. The water level in the river and during floods in the flood plain is in direct correlation to discharge from the catchment area. According to the space available and the roughness of the riverbed, the banks and the river foreland, a certain discharge rate causes a corresponding water level. This relationship can be described for single points along the watercourse as the ratio between water level and discharge. High water events are generally expressed in m3/s â&#x20AC;&#x201C; the discharge volume and not the water level. Different water levels, both low and high water, have diverse consequences for the ecosystem and human use: while high water and floods present a danger for the riverside areas and can permanently alter the composition of species in an ecosystem through the power and depth of flooding, low water can cause serious problems for shipping and power station cooling systems. Should the water level sink very low or the watercourse dry up completely, this also places tremendous strain on the ecosystem.

Leine

500

Main Isar

400 300 200 100 0 J

2008 cm 500 400 300 200 100 0 1

05. 2010

cm 500 400 300 200 100 0 0h

12h

18h

15. 04. 2010

Each river has an individual flood pattern. The water level of a river changes continuously, even though generally only the extremes of flood and low water are noticed.

Sub-process 2: lateral spread of the water High water is especially conspicuous through flooding; minor rises in discharge levels can usually be contained within the river channel, but with larger high water events the river overflows its banks and covers the adjacent flood plain. This has a corrective effect: in flooding the foreland, which generally has a higher roughness, the waterâ&#x20AC;&#x2122;s energy is dissipated and its height and speed reduced. Flooding is limited, when the river is not shaped by human measures, to the valley borders. Flood protection measures such as dikes cause an artificial limitation on the spread of the water and thus the flood area.

20 2â&#x2C6;&#x201A;

Fundamentals Water Processes

The primary current carries water down the valley. The secondary current arises within the channel: along its central course, two contra-rotating spiral flows are created.

Reversible sediment shift processes: migrating gravel banks in the Isar River in Munich

Morphodynamic processes The appearance of a river in the landscape represents the result of a manifold and complex morphodynamic development. The driving force is the river current, which on account of its numerous and complex sub-processes can barely be described comprehensively through scientific methodology. Exact predictions of how a river channel will develop are therefore not possible. The primary current carries the water down the valley. Secondary current is the rotation of water around the main flow direction; this is caused by the different flow rates near the banks, where the water is slowed by friction, and in the middle of the channel, where it flows faster. A secondary flow is created that pushes the water at the sides upwards and draws it down in the middle. Two contrary spiral flows are formed. In bends of the river the outer spiral flow is concentrated and accelerated, while in the inside curve the flow is slowed down because the distance covered is shorter. The flow of water causes erosion and sedimentation along the watercourse that subjects the river space to continuous morphological alteration. In these morphodynamic processes, that of sedimentation shift (sub-process 1) within the watercourse can be distinguished from shifts in the channel itself (sub-process 2). Sedimentation shifts in the watercourse are mainly expressed through the characteristics and structuring of the riverbed, and are to some extent reversible. With the inherent dynamic of the river channel, however, the river shifts its course and brings about irreversible restructuring across the whole river space.

Process Space

Embankment Walls and Promenades

â&#x2020;&#x2019;

Design Strategy

A6 Adapting

Introduction

â&#x2020;&#x2019;

Design Tool

A6.2 Floating islands

Process Spaces

Embankment Walls and Promenades

Limits Limits process space Flood limits Limits of self-dynamic river channel development Riverbed reinforcement

Limits of vertical water level fluctuation

Dikes and Flood Walls Processes

Limit of vertical water level fluctuation Horizontal spread Sedimentation shift

Flood Areas

Sedimentation Erosion Undercut bank Sediments

D E

Riverbeds and Currents

Dynamic River Landscapes

things. Each design strategy combines several practical design tools or measures that have all been influenced by this attitude. In Process Space A, for example, all the designs primarily address vertical fluctuations in the watercourse. One design strategy is to shape elements in such a way that they can be submerged when the water level rises without suffering damage. They are capable of ‘tolerating’ the rising water. Another strategy is to design elements to ‘adapt’ to rising water levels, as houseboats or floating jetties do. The spectrum of various design strategies makes it clear how many different ways there are within each Process Space of dealing with the respective water dynamics through design. Analysing the case studies made it possible to identify between four and six discrete strategies for each Process Space.

Design tools and measures

The individual design measures employed on site were identified using plans, literature, discussions and visits, subsequently abstracted in the form of transferable design tools and depicted in schematic sections or plans. Design tools can range from the smallest of measures such as individual seating areas by the riverside through to large-scale interventions such as the construction of retention areas. Two significant criteria had to be met before a design tool was included in the catalogue: constructive examination of and involvement with the watercourse dynamics, and multifunctional intervention. Preference was given to tools that responded creatively to the complex demands of urban water spaces and that could serve as a source of inspiration for future projects. The catalogue makes no claim to be a comprehensive list of all the possible design measures for watercourses, but is intended to offer many and varied suggestions for use in other designers’ work on water projects through its transferable design approaches and practical examples. The principle of each design tool is presented with a sectional or plan drawing and illustrated with a photograph of a project example. Links are indicated from each design tool to the projects in Part 3, while the Project Catalogue includes references back to explanations in the Design Catalogue of the design tools used in each project.

Combinations of design tools Hardly any design task for urban water spaces can be resolved using a single design tool; frequently, several design tools are combined within a Process Space. Proceeding from the experience gathered through our analysis of the case studies on combinations that often occur in practice or complement each other well, suggestions for combining design tools are made in the Design Catalogue. Each design strategy has a list of recommended combinations with design tools from other strategies: for example, flood protection walls (B2.1) from the list of B2 (Vertical resistance) strategies can be easily combined with a dike park concept (B1.1 Dike parks) by integrating the wall as a seating element or spatial organisation feature. The wall could just as easily be enhanced with mobile flood protection elements (B5.1-5.3) that make openings and windows in the wall possible.

40 4∂

Design Catalogue Introduction

List of process spaces and design strategies

Embankment Walls and Promenades

Dikes and Flood Walls

A∂

B∂

Linear spatial expansion

Differentiating resistance ∫ 72

∫ 52

Selective spatial expansion

Vertical resistance

∫ 54

∫ 76

Temporary resistance

Reinforcing resistance

∫ 56

∫ 78

Placing over the water

Integrating resistance

∫ 58

∫ 80

Tolerating

Temporary resistance

∫ 60

∫ 82

Adapting

Making river dynamics evident

∫ 64

∫ 84

Flood Areas

Riverbeds and Currents

Dynamic River Landscapes

C∂

D∂

E∂

Extending the space

Deflecting the current

∫ 92

∫ ∂∂4

Allowing channel migration ∫ ∂34

Placing over the water

Grading the channel

∫ 96

∫ ∂∂8

Initiating channel dynamics ∫ ∂36

Tolerating

Varying the riverbed

Creating new channels

∫ ∂20

∫ ∂38

Evading

Varying the bank reinforcement

Restricting channel dynamics

∫ ∂22

∫ ∂40

∫ ∂00

∫ ∂04

Adapting

Varying the riverbed reinforcement

∫ ∂06

∫ ∂26

42 43

Design Catalogue Introduction

List of design tools and design measures

A A∂

Embankment Walls and Promenades

Linear spatial expansion ∫ 52

A∂.∂ Intermediate levels ∫ 53

B B∂

Dikes and Flood Walls

Differentiating resistance ∫ 72

A∂.2 Terraces ∫ 53

B∂.∂ Dike parks ∫ 73 B∂.2 Trees on dikes ∫ 73

A∂.3 Broad riverbank steps ∫ 53

B∂.3 Reprofiling the dike section ∫ 74

Selective spatial expansion ∫ 54

A2.∂ River access parallel to the bank ∫ 55 A2.2 River access perpendicular to the bank ∫ 55 A3

Temporary resistance ∫ 56

A3.∂ Closable access ∫ 57 A3.2 Retaining sightlines ∫ 57

B∂.4 Dikes as path networks ∫ 74 B∂.5 Dike steps and promenades ∫ 74 B∂.6 Superdikes ∫ 75 B2

Vertical resistance ∫ 76

B2.∂ Integrating flood

protection walls ∫ 77 B2.2 Influencing perceptions ∫ 77

Placing over the water ∫ 58

of the wall height

A4.∂ Balconies ∫ 59 A4.2 Overhangs ∫ 59

A4.3 Suspended pathways ∫ 59

B3.∂ Invisible stabilisation ∫ 79 B3.2 Glass walls ∫ 79

Tolerating ∫ 60 A5.∂ Underwater steps ∫ 6∂ A5.2 Boulders and stepping stones ∫ 6∂ A5.3 Foreshores ∫ 6∂ A5.4 Submergible riverside paths ∫ 62 A5.5 Submergible boardwalks ∫ 62 A5.6 Surmounting the embankment wall ∫ 62 A5.7 Submergible furniture ∫ 63 A5.8 Submergible planting ∫ 63 A5.9 New embankment walls ∫ 63

Adapting ∫ 64 A6.∂ Floating jetties ∫ 65 A6.2 Floating islands ∫ 65 A6.3 Moored ships ∫ 65 A6

Reinforcing resistance ∫ 78

Integrating resistance ∫ 80 B4.∂ Using the historical city wall ∫ 87 B4.2 Watertight facades ∫ 8∂ B5 Temporary resistance ∫ 82 B5.∂ Portable protection elements ∫ 83 B5.2 Attachable protection elements ∫ 83 B5.3 Fold-out protection elements ∫ 83 B6 Making river dynamics evident ∫ 84 B6.∂ High water marks ∫ 85 B6.2 Art objects and furniture ∫ 85

C C∂

Flood Areas

Extending the space ∫ 92

C∂.∂ Setting back the dike ∫ 93 C∂.2 Branches ∫ 93 C∂.3 Flood channels ∫ 93 C∂.4 Reprofiling the flood plain ∫ 94 C∂.5 Backwaters ∫ 94 C∂.6 Polder systems ∫ 94 C∂.7 Retention basins ∫ 95

Placing over the water ∫ 96 C2.∂ Mounds ∫ 97 C2.2 Mound principle with buildings ∫ 97 C2.3 Buildings on piles ∫ 98 C2.4 Escape routes ∫ 98 C2.5 Cableways ∫ 99 C2

Tolerating ∫ ∂00

C3.∂ Paths within the flood plain ∫ ∂0∂ C3.2 Sports facilities and playgrounds ∫ ∂0∂ C3.3 Flood-tolerant buildings ∫ ∂0∂ C3.4 Parks within the flood plain ∫ ∂02 C3.5 Extensive natural areas ∫ ∂02 C3.6 Agriculture ∫ ∂03 C3.7 Camping and caravan sites ∫ ∂03 C3.8 Events grounds ∫ ∂03 C4

Evading ∫ ∂04

C4.∂ Warning signs and barriers ∫ ∂05

D D∂

Riverbeds and Currents

Deflecting the current ∫ ∂∂4

D∂.∂ Large single rocks ∫ ∂∂5 D∂.2 Dead wood ∫ ∂∂5 D∂.3 Laid stone groynes ∫ ∂∂5 D∂.4 Piled stone groynes ∫ ∂∂6 D∂.5 Bioengineered groynes ∫ ∂∂6 D∂.6 Submerged groynes ∫ ∂∂6 D∂.7 Riverbed sills ∫ ∂∂7 D2 Grading the channel ∫ ∂∂8 D2.∂ Widening the channel ∫ ∂∂9

Dynamic River Landscapes

Allowing channel migration ∫ ∂34 E∂.∂ Removing riverbank and riverbed reinforcement ∫ ∂35 E∂.2 Semi-natural riparian management ∫ ∂35 E∂.3 Regulating water extraction ∫ ∂35 E∂

D3 Varying the riverbed ∫ ∂20

Initiating channel dynamics ∫ ∂36 E2.∂ Reprofiling the channel cross-section ∫ ∂37 E2.2 Introducing disruptive elements ∫ ∂37 E2.3 Adding bed load ∫ ∂37

D3.∂ Sand and gravel beaches on inner bends ∫ ∂2∂

D2.2 Extending the flow length ∫ ∂∂9

D3.2 Sand and gravel beaches in bays ∫ ∂2∂ D3.3 Creating scour holes ∫ ∂2∂ D4 Varying the bank reinforcement ∫ ∂22 D4.∂ Partially naturalising the riverbank ∫ ∂23 D4.2 Living revetment ∫ ∂23 D4.3 Stone revetment ∫ ∂24 D4.4 Terraced stone revetment ∫ ∂24 D4.5 Masonry riverbank revetment ∫ ∂24 D4.6 Building over the existing reinforcement ∫ ∂25

Creating new channels ∫ ∂38 E3.∂ Creating meanders ∫ ∂39 E3.2 Incorporating a straightened channel ∫ ∂39 E3.3 Creating multiple channels ∫ ∂39 Restricting channel dynamics ∫ ∂40 E4.∂ ‘Sleeping’ riverbank reinforcement ∫ ∂4∂ E4.2 Bank reinforcement as needed ∫ ∂4∂ E4.3 Selective bank reinforcement ∫ ∂4∂ E4

C4.2 Electronic warning systems ∫ ∂05

Adapting ∫ ∂06 C5.∂ Floating and amphibious houses ∫ ∂07 C5.2 Marinas ∫ ∂07 C5

D5 Varying the riverbed reinforcement ∫ ∂26 D5.∂ Fish passes ∫ ∂27 D5.2 Varying the riverbed and transverse structures ∫ ∂27 D5.3 Ramps and slides ∫ ∂27

44 45

Design Catalogue Introduction

Embankment Walls and Promenades

Leine, Hanover

From a hard embankment edge to a differentiated riverside area. Through the transformation, the boundary lines lose their separating character and a usable transitional area between water and land emerges. The scope for action is frequently limited to the steep embankment wall itself. 46 47

Design Catalogue Embankment Walls and Promenades

A∂ Linear spatial expansion

∫ All design tools in A∂ can be combined with – – – – – – – – A3.∂ Closable access A5.∂ Underwater steps A5.2 Boulders and stepping stones A5.3 Foreshores A6.∂ Floating jetties A6.3 Moored ships

This design strategy presents various linear expansion possibilities to differentiate the riverbank more strongly and at the same time create somewhat more space for the water to spread sideways. This is achieved by terracing the riverbank walls. The flood limit (green line) shifts landwards, and the waterside area is stepped in terraces or stairs. This creates differentiated spaces within the flood area allowing direct access to the water. Elements made entirely of masonry or concrete such as steps are possible, but so are grassed terraces; the important factor is their resistance to erosion, as the terraces or riverbank steps also serve as bank revetment. They determine the edge of the watercourse (red line) and at the same time allow access to the water. The terraces or steps can be confined to a small stretch, or line a longer linear run along the watercourse. Spaces thus created are exposed, according to the height of the terraces, in varying degrees by fluctuations in flood levels; the height of the terraces determines the level and frequency with which they are flooded. Fluctuations in discharge are thus appreciably different, compared to the previous steep riverbank wall; for instance, the number of submerged steps make fluctuations discernible – how many steps are underwater today? Various design tools employ this strategy and differ in the design of the height and breadth of the steps or terraces used; the decision in favour of smaller or larger steps has an immediate bearing on possible uses for the new spaces – as steps, as seating or as intermediate terraces. This reconfiguration of the riverbank makes it possible to directly interweave the urban structure with the water space and can thus elevate formerly insignificant or degraded watercourses into prominent parts of the townscape and make them accessible again. Direct contact with the water is facilitated, and uses such as swimming or canoeing are made possible.

A∂.∂

A∂.2

A∂.3

Intermediate levels

Terraces

Broad riverbank steps

Nahe, Bad Kreuznach

Rhône, Lyon

Nahe, Bad Kreuznach

A broader intermediate level offers spaces for lingering by the waterside and temporary uses such as summer cafés. This element, frequently used over longer sections of a river, is conceivable when space is limited. The divisive character of a vertical riverbank is ameliorated and the flood area is improved by broadening the cross-section. In Bad Kreuznach, such a space was created with boat hire and a café by the water.

A staged transition to the water over several broad terraces permits several uses to coexist: in Lyon, ball games areas were laid out beside tree plantings. The design emphasises the twofold function of this area, on one hand access to the river and on the other an interesting recreational area beside the river. To develop its effect fully, this approach is suitable for longer stretches of a river. A gradual transition to the adjacent urban space can be created, without a perceptibly hard borderline.

Broad riverbank steps create public space beside the water, offering direct contact with the river at various water levels. By opening new sightlines they can achieve striking connections between the urban surroundings and the river. Diverse structuring of the steps enhances their various functions as movement spaces and pleasant places to linger, similar to the tiers of a sports stadium. The new riverside steps in Bad Kreuznach open up a wide vista to the surroundings.

Rhône, Lyon Δ ∂60

– – – – – – – –

Nahe, Bad Kreuznach Δ ∂84

Limmat, Zurich, Factory by the Water Δ ∂56

Elster and Pleiße Millraces, Leipzig

Rhône, Lyon Δ ∂60

Δ ∂50

Nahe, Bad Kreuznach Δ ∂84

Limmat, Zurich, Wipkingerpark Δ ∂58

+ Limmat, Zurich, Bathing Facility Oberer

IJssel, Doesburg Δ ∂72

Letten Δ 280

Nahe, Bad Kreuznach Δ ∂84

– – – – – – – – Leine, Hanover Δ ∂54

+ Elbe, Hamburg, New Elbe Promenade Δ 279

52 53

Design Catalogue Embankment Walls and Promenades

Selective spatial expansion

∫ All design tools in A2 can be combined with – – – – – – – – A∂.2 Terraces A3.∂ Closable access A5.2 Boulders and stepping stones A5.3 Foreshores A5.8 Submergible planting

Unlike A1, here the continuous vertical limitation on the space is breached at just one location or opened at a selected point. Narrow access to the water via a ramp or terrace is created, ending in a beach situation sloping into the riverbed. This gently sloping access can be used as bathing beach, waterside playground, slipway or canoe landing place. As with design strategy A1 (Linear spatial expansion), the flood limit (green line) is pushed back, and the space that emerges is subject to variations in the water level; fluctuations in the river volume flow rate can be appreciated, in contrast to steep embankment wall, through the water spreading sideways. Depending on how the idea is executed, the bank reinforcement (red line) can be dispensed with at the beach cove that is created. As a calm area of water is created in the shallow inlet, currents are weaker and the slower flow means that sedimentation can be expected. Depending on the type of watercourse, a gravel or sandy beach can develop or mud can accumulate. The zones with reduced flow rate act as small ecological niches. In heavily built-up urban watercourses, usually with high flow rates, such a marginal foreshore offers space for special riparian plants, the various sediments enhance biotope diversity, and waterland access is created for amphibians and mammals. Thus, despite the artificiality of the watercourse, small habitats can develop. The two design tools shown here demonstrate possibilities of making selective periodic openings to the water. Choosing the direction in which access is laid – parallel to the bank (A2.1) or perpendicular to the bank (A2.2) – has various consequences for the organisation of the surrounding space.

A2.∂

A2.2

River access parallel to the bank

River access perpendicular to the bank

Leine, Hanover

Limmat, Zurich, Factory by the Water

Wupper, Müngsten

Where the riverbank wall is breached at a single point a place to linger at the waterside can be created. One space-saving solution to access this place and overcome the height difference is with steps or a ramp from the promenade running parallel to the riverbank. In Hanover, on the socalled Hohes Ufer and next to the floating café Leine Suite, a ramp-like pathway allows immediate access to the River Leine.

In the ‘Factory by the Water’ project (Fabrik am Wasser) on the River Limmat in Zurich an old, formerly filled-in branch canal was used to re-establish terraced access to the water.

An opening to the watercourse at right angles to the bank is the spatial counter-concept to parallel access (A2.1). The foreland topography is more strongly influenced, as the access cuts into the higher land. The angle of the embankment determines the length of the access, opening charming views of the water from above. The ‘Brückenpark Müngsten’ employs an alternation of open spaces far from the waterline and beach-like inlets.

– – – – – – – – Leine, Hanover Δ ∂54 Limmat, Zurich, Factory by the Water Δ ∂56

– – – – – – – – Wupper, Wuppertal Δ ∂68 Wupper, Müngsten Δ 230 Ahna, Kassel Δ 234 Soestbach, Soest Δ 248

54 55

Design Catalogue Embankment Walls and Promenades

A3 Temporary resistance

∫ All design tools in A3 can be combined with – – – – – – – – A∂.∂ Intermediate levels A∂.2 Terraces A2.∂ River access parallel to the bank A2.2 River access perpendicular to the bank A5.4 Submergible riverside paths A5.5 Submergible boardwalks B6.∂ High water marks

Movable flood protection elements can supplement protective walls when there is a threat of flooding and also offer an opportunity to create breaks in the walls or build walls of more moderate height. Movable elements are only used temporarily, during periods of high water. However, their permanent mountings and closable watertight flood doors or windows make design references to the high water events; the visibility of protection measures sensitises people to the danger of flooding. The use of movable elements requires a sophisticated flood protection strategy, including operational planning to erect the elements storage facilities. Sufficient advance warning of flood events is also a precondition for the use of such elements. Preserving views (A3.2 Retaining sightlines) and accessibility (A3.1 Closable access) by using movable elements means that urban spaces which need a higher level of flood protection can maintain a close relationship to the river. Depending on how high above mean water level the elements are installed, they may be intended for use only rarely, in times of extreme flood events, or may need to be installed and dismantled again fairly frequently.

A3.∂

A3.2

Closable access

Retaining sightlines

Waal, Zaltbommel

IJssel, Kampen

Openings in flood protection walls can create direct access to areas which are subject to flooding. For example, closable doors or gaps are installed that are a precondition for use of the open space in front of the flood protection line. Both movable, temporary dam beams and permanently installed watertight gates or shutters are feasible. In Zaltbommel, a gap that can be sealed with a dam beams affords access to the lower lying harbour area.

By installing removable flood bariers or window flaps, sightlines and visual connections can be retained despite the need to increase the height of flood protection structures. Along with a clear view from the city to the water, the vista from the water or across the river to historical town waterfronts can be kept open. In Kampen, using temporary elements that can be mounted on top of the wall means that views of the river IJssel and the historical townscape remain uninterrupted.

– – – – – – – – Seine, Choisy-le-Roi Δ ∂64

– – – – – – – –

IJssel, Kampen Δ ∂74

Nahe, Bad Kreuznach Δ ∂84 Waal, Zaltbommel Δ ∂90

56 57

Design Catalogue Embankment Walls and Promenades

Dynamic River Landscapes

Isar, Munich

From constrained channel to dynamically meandering river â&#x20AC;&#x201C; the static riverbank reinforcement at the mean water line is shifted or removed, and a river space with its own developmental dynamics evolves in which, over a long period, the banks and the position of the entire channel can continually change. â&#x2C6;&#x201A;28 â&#x2C6;&#x201A;29

Design Catalogue Dynamic River Landscapes

E∂

Allowing channel migration

∫ All design tools in E∂ can be combined with – – – – – – – – C∂.4 Reprofiling the flood plain C3.5 Extensive natural areas E2.∂ Reprofiling the channel cross-section E2.2 Introducing disruptive elements E2.3 Adding bed load E3.∂ Creating meanders E3.3 Creating multiple channels E4.∂ ‘Sleeping’ riverbank reinforcement E4.2 Bank reinforcement as needed E4.3 Selective bank reinforcement

The simplest and most radical way of restoring a river to its natural fluvial dynamics is to remove the existing riverbank reinforcements and thereby the limits on its self-dynamic development. The riverbank revetment and low weirs that seal the bed and define the river’s course are taken out. One objective of this strategy is that the watercourse can attain a quasi-natural state with a meandering channel without additional human intervention, solely through its own dynamic processes. If a river is capable of regaining its dynamic equilibrium within a reasonable period, then this approach without artificial interventions is advantageous for both economic and ecological reasons. If a river has been drastically straightened, however, just removing the riverbank reinforcement is often insufficient; when a watercourse has very little dynamic of its own it can take decades to achieve semi-natural structures, while if the flow rates are fast, with correspondingly high tractive forces, there is a danger that the watercourse will cut too deeply into the bed at first until a form develops within which dynamic equilibrium can evolve. When removing the riverbank reinforcement, adapting the channel maintenance regime is an important aspect. Traditional river channel maintenance is usually concerned with keeping the discharge cross-section clear and thus passing water downstream as fast as possible. Responsibility for channel maintenance rests with the respective owner – in Germany the municipal water and ground authority for smaller watercourses and the national waterways and shipping administration for major rivers – whose traditional role was limited to maintaining a defined condition of each river – the riverbed was regularly desilted, aggradations and scour holes removed, the banks reinforced or shored up after collapsing, and riverbank vegetation regularly mown. Today channel maintenance – in Germany following the new version of the water resources law (WHG) of 31 July 2009 – pursues the aim of ecological enhancement of rivers with stronger self-dynamic channel development, encouraged through the introduction of ‘disruptive’ elements (see also E2 Initiating channel dynamics). Crucially, it must be realised that this self-dynamic development requires sufficient space. Removing steep riverbank reinforcement has direct and positive consequences for the accessibility of the river. Permitting natural vegetation and aggradation processes enhances the experiential quality but can also convey an impression of unkemptness and running wild. To ensure that such measures are welcomed by local residents and to assuage their concerns, a broad-based information campaign and opportunities for citizen involvement are recommended.

E∂.∂

E∂.2

E∂.3

Removing riverbank and riverbed reinforcement

Semi-natural riparian management

Regulating water extraction

Wahlebach, Kassel

Losse, Kassel

Isar, Munich

Taking out the riverbank and riverbed reinforcement can happen either in its entirety or in part – the type and extent of the intervention will influence the river’s inherent dynamic and its channel development. Removal of bank reinforcements can, for example, be on just one side, as on the River Isar in Munich, or on both sides along a considerable stretch of the watercourse as on the Wahlebach stream in Kassel. It is possible to reuse the removed materials as disruptive elements on the riverbed or to build a new flood protection line.

More extensive, adaptive channel maintenance permits natural development processes in flowing water. Abandoning measures such as regular desilting and the removal of aggradations, scour holes and bank collapses while permitting or deliberately introducing disruptive elements such as dead wood or aquatic plants leads to differentiation in the flow pattern and works on the riverbed to initiate sedimentation and erosion processes. The river’s self-dynamic channel development of a meandering course with cut banks and slip-off banks begins. On the delta of the River Losse in Kassel, once the works had been completed, refraining from regular maintenance has actually been the design tool that allows the river’s own dynamic to create new branches and vegetation zones. It is only when the situation is critical, for example when floodwater backs up or erosion goes too far, that conventional riparian management measures are employed.

Large amounts of water are taken from some rivers by hydroelectric power stations with supply canals, as along the River Isar in Munich, and for the irrigation of agricultural land in dry areas, leaving – especially in the dry summer months – very little water (‘residual water’) in the watercourse. On the one hand this has a negative effect on the appearance and ecology of the river, and on the other it is insufficient to drive the self-dynamic river channel development. By adjusting water extraction the residual water quantities can meet the ecological and aesthetic needs of the river; this can, as in Munich, mean curbing or even interrupting power station operations in especially dry months.

– – – – – – – – Emscher, Dortmund Δ 256 lsar, Munich Δ 260 Schunter, Braunschweig Δ 266 Wahlebach, Kassel Δ 268 Werse, Beckum Δ 270

– – – – – – – – Isar, Munich Δ 260

– – – – – – – – Kyll, Trier Δ 2∂0 Emscher, Dortmund Δ 256 Losse, Kassel Δ 264 Schunter, Braunschweig Δ 266 Werse, Beckum Δ 270

∂34 ∂35

Design Catalogue Dynamic River Landscapes

Initiating channel dynamics

∫ All design tools in E2 can be combined with – – – – – – – – C∂.4 Reprofiling the flood plain C3.5 Extensive natural areas E∂.∂ Removing riverbank and riverbed reinforcement E∂.2 Semi-natural riparian management E3.∂ Creating meanders E3.2 Incorporating a straightened channel E3.3 Creating multiple channels E4.∂ ‘Sleeping’ riverbank reinforcement E4.2 Bank reinforcement as needed E4.3 Selective bank reinforcement

Selective interventions in the river, in the form of specific shifting of substrate along the banks or on the riverbed, stimulate morphodynamic processes. This strategy is applied when the desired effect of channel development out of the river’s inherent dynamic would come about only after a very long time. Its aim is to optimise the framework conditions for the inherent dynamics to create a structurally rich watercourse more quickly. These redeployments, then, serve merely to prime a strong internal dynamic under which the initial condition of the river will quickly disappear. Within a short period, varied habitats can arise that facilitate speedy colonisation by flora and fauna. At the same time the appearance of the river can also alter quickly, making it easier to communicate the intervention to the public although the actual course of the river channel is not changed at first. Most design tools to introduce morphodynamic processes exert an influence on the currents in the river, setting erosion and sedimentation processes in motion through their specific variation. Broadening the river at certain points slows down the flow and thus creates aggradations, while disruptive elements placed in the current can deflect it towards one bank and initiate erosion. As design leitmotif, it is possible to strive for a semi-natural appearance, for instance by using dead wood, or conversely to make the deflection of the current obvious by using plainly artificial elements. Introducing disruptive elements also means expanding habitat diversity, and stepping stones can facilitate direct contact with the water. A further option is to influence the framework conditions for the discharge and sediment transport processes. Direct mechanical deposition of sediment on the riverbed makes it easier for sand- and gravel banks or natural beaches to arise, while stimulating the discharge dynamics reinforces the operative forces and thus accelerates developments.

E2.∂

E2.2

E2.3

Reprofiling the channel cross-section

Introducing disruptive elements

Adding bed load

Isar, Munich

Schunter, Braunschweig

Isar, Munich

Excavating the flood plain and flattening out the banks makes it possible for the river to develop beyond the former riverbank line. Selective excavations or shifting substrate within the riverbed creates sinks or shallow water zones; varying the crosssection raises the flow variation and a low water channel is created in the fasterflowing areas which serves to sustain the continuity of flow even during an extreme drought. Depending on the speed of the current, sediments of various particle sizes settle on the riverbed, as on the Isar in Munich, ranging from sand through gravel to larger stones – thus further enhancing the river’s structural diversity.

Disruptive elements are set at specifically chosen places in the riverbed to deflect the current towards the bank and catalyse erosion processes, or to encourage sedimentation on their sheltered downstream side. Disruptive elements can be just as well attached to the bank as placed in midstream. On the Schunter in Braunschweig fixed dead wood is used to divert the current and thus erode the opposite riverbank and create a steep slope. The disruptive elements enhance structural diversity and provide places to play and linger by on the waterside.

Many urban rivers lack natural sedimentation. Weirs or other cross-stream structures hinder the movement of bed load and the rivers suffer from sediment deficit. Deliberate deposition of sediments typical for the river provides material for riverbed enhancement. On the Isar in Munich, artificial sand or gravel banks were dumped, to be carried further downstream by the next high water event. If the lack of bed load is caused by weirs and ground sills, single openings in the structure can let the bed load overcome the barriers and contribute to the development of the next stretch of river.

– – – – – – – – Isar, Munich Δ 260

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Losse, Kassel Δ 264

Isar, Munich Δ 260

Emscher, Dortmund Δ 256

Schunter, Braunschweig Δ 266

Isar, Munich Δ 260

Werse, Beckum Δ 270

Wahlebach, Kassel Δ 268 Werse, Beckum Δ 270

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Design Catalogue Dynamic River Landscapes

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Process Space A: Embankment Walls and Promenades Elster and Pleiße Millraces, Leipzig, Germany: New Riverbanks ∆ ∂50 Leine, Hanover, Germany: Leine Suite ∆ ∂54 Limmat, Zurich, Switzerland: Factory by the Water ∆ ∂56 Limmat, Zurich, Switzerland: Wipkingerpark ∆ ∂58 Rhône, Lyon, France: Berges du Rhône ∆ ∂60 Seine, Choisy-le-Roi, France: Quai des Gondoles ∆ ∂64 Spree, Berlin, Germany: Bathing Ship ∆ ∂66 Wupper, Wuppertal, Germany: Wuppertal 90° ∆ ∂68

Process Space B: Dikes and Flood Walls IJssel, Doesburg, the Netherlands: IJsselkade Residential Area ∆ ∂72 IJssel, Kampen, the Netherlands: Flood Protection in Kampen-Midden ∆ ∂74 Main, Miltenberg, Germany: Flood Management Concept ∆ ∂78 Main, Wörth am Main, Germany: Flood Management for the Old Town ∆ ∂80 Nahe, Bad Kreuznach, Germany: Flood Management Concept ∆ ∂84 Waal, between Afferden and Dreumel, the Netherlands: Tapered Dike ∆ ∂88 Waal, Zaltbommel, the Netherlands: Waalkade Promenade ∆ ∂90

Process Space C: Flood Areas Bergsche Maas, between Waalwijk and Geertruidenberg, the Netherlands: Overdiepse Polder ∆ ∂94 Besòs, Barcelona, Spain: Ecological Restoration ∆ ∂96 Ebro, Zaragoza, Spain: Parque del Agua ∆ ∂98 Elbe, Hamburg, Germany: HafenCity ∆ 202 Gallego, Zuera, Spain: Parque Fluvial ∆ 204 IJssel, Zwolle, the Netherlands: Vreugderijkerwaard ∆ 208 Kyll, Trier, Germany: Renaturation of the Kyll Mouth ∆ 2∂0 Maas, Maasbommel, the Netherlands: Floating Homes in Gouden Ham ∆ 2∂2 Petite Gironde, Coulaines, France: Parc de la Gironde ∆ 2∂4 Rhine, Brühl, Germany: Koller Island Polder ∆ 2∂8 Rhine, Mannheim, Germany: Riverbank Renaturation and Lido Restaurant on Reiß Island ∆ 220 Seine, Le Pecq, France: Park Corbière ∆ 222 Waal, Gameren, the Netherlands: Gamerense Waard Flood Plain Renaturation ∆ 224 Wantij, Dordrecht, the Netherlands: Plan Tij Housing Estate ∆ 228 Wupper, Müngsten, Germany: Müngsten Bridge Park ∆ 230

Process Space D: Riverbeds and Currents Ahna, Kassel, Germany: Renaturation ∆ 234 Alb, Karlsruhe, Germany: Near-natural Restoration ∆ 236 Birs, Basle, Switzerland: Birsvital ∆ 238 Leutschenbach, Zurich, Switzerland: Restoration ∆ 240 Neckar, Ladenburg, Germany: Green Ring ∆ 242 Seille, Metz, France: Parc de la Seille ∆ 246 Soestbach, Soest, Germany: Daylighting of the Soestbach ∆ 248 Wiese, Basle, Switzerland: Revitalisation ∆ 250 Wiese, Lörrach, Germany: Wiesionen ∆ 252

Process Space E: Dynamic River Landscapes Emscher, Dortmund, Germany: Retention Basin Mengede and Ellinghausen ∆ 256 Isar, Munich, Germany: Isar-Plan ∆ 260 Losse, Kassel, Germany: Losse Delta ∆ 264 Schunter, Braunschweig, Germany: Restoration ∆ 266 Wahlebach, Kassel, Germany: Near-natural Restoration ∆ 268 Werse, Beckum, Germany: Near-natural Development ∆ 270

Embankment Walls and Promenades

â&#x2C6;&#x201A;48 â&#x2C6;&#x201A;49

Project Catalogue Embankment Walls and Promenades

Leine, Hanover

Limmat Wipkingerpark, 2003–2004 Zurich, Switzerland River data for project area Catchment area: 2176 km2 Mean discharge (MQ): 96 m3/s One-in-100-year flood discharge (HQ100): 590 m3/s Width of riverbed: 60 m; Width of flood plain: 70 m Location: 47° 23’ 43’’ N – 08° 30’ 16’’ E

The riverside as contact space ∫ Design tools – – – – – – – – A∂.3 Broad riverbank steps A5.∂ Underwater steps A5.2 Boulders and stepping stones

A number of different interventions have turned a hitherto unused section of the Limmat with its derelict riverbank wall into a public park. Within a densely populated neighbourhood and a section of the riverside that is still being used by industry, a new public place near the water’s edge has been created. With regard to design, considerable emphasis has been put on the zone where the water meets the land. The riverside was made accessible to pedestrians by flattening the ground and building a 180 m long path with steps; its particular design offers promenaders the opportunity to come into contact with the water. The last step lies below the water surface making the water accessible right into the river. As an additional measure, the concrete flight of steps that leads down to the water was extended into the Limmat for another 12 m using roughly hewn granite boulders. For that purpose, the embankment zone was slightly raised. The surfaces of the stones lie either just below the water level or just above it.

Visible dynamics

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Project Catalogue Embankment Walls and Promenades

The rough surfaces of the stones break the current of the river, dramatising its flow as a visual and haptical experience. Through these stepping stones the river itself becomes accessible. The subtle level differences of the stones make even minor water fluctuations recognisable. At low water levels, one can walk far into the river, but if the water is high even those stepping stones that are usually well above the water surface are submerged. Apart from giving access to the water, the stones interrupt the flow of the river causing varying currents. This also creates an artificial shallow water zone in the Limmat, which, in the strong current of the river, may serve as a resting zone for fish and as a small enclave and rare habitat for some animal and plant species. The

flight of steps also reinforces the riverbank. In this way, both sedimentation and erosion processes are prevented. The straightforward line of the concrete steps is interrupted by roughly hewn granite boulders as well as the loosely arranged stepping stones at their bases. The design of the stairs also dramatises the transition from the artificial element of the park to the natural element of the river. Both the stepping stones and the baffles look like broken-off or eroded fragments of the stairs. They highlight the natural dynamics of the water without pretending to imitate the forms of a natural watercourse.

1 The new steps [Aâ&#x2C6;&#x201A;.3] reach far into the water. The varying water levels are clearly recognisable and influence how the riverside is used. 2 Schematic section: Alongside the stairs, the embankment was sloped in order to create a shallow water zone which can be accessed via the stepping stones. 3 Depending on the water level, the stepping stones are either submerged or reach well out of the water. 4 Fishing, sunbathing, strolling along the waterâ&#x20AC;&#x2122;s edge â&#x20AC;&#x201C; the steps near Wipkingerpark can be used in many different ways. 5 The stepping stones look like broken-off fragments of the stairs. 6 The new park with its promenade, the generous flight of steps and the small stepping stones and baffles in front [A5.2].

Rhône Berges du Rhône, 2004–2007 Lyon, France River data for project area Catchment area: ~ 20 300 km2 Mean discharge (MQ): ~ 600 m3/s One-in-50-year flood discharge (HQ50): ~ 4150 m3/s Width of riverbed: 150 m; Width of flood plain: 160–220 m Location: 45° 45’ 26’’ N – 04° 50’ 24’’ E

∫ Design tools – – – – – – – – A∂.∂ Intermediate levels A∂.2 Terraces A∂.3 Broad riverbank steps A4.∂ Balconies A5.4 Submergible riverside paths A5.6 Surmounting the embankment wall A5.7 Submergible furniture A5.8 Submergible planting A6.3 Moored ships D3.∂ Sand and gravel beaches on inner bends D4.6 Building over the existing reinforcement

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Project Catalogue Embankment Walls and Promenades

The riversides of the Rhône were practically cut off from the amenities of Lyon by a busy street, and cars were parked on the wharfage immediately next to the water. ‘The design of the 5 km long stretch along the Rhône banks in Lyon was aimed at creating a new open space in the inner city, strengthening nature’s presence in the town and making the river accessible for the inhabitants’, explained David Schulz, project manager of the landscape design practice In Situ Architectes-Paysagistes. The first step was to reduce the space for riverside roads in the re-landscaped section, which links the Parc de la Tête d’Or in the North with the Parc de Gerland in the South and to move stationary traffic to an underground car park, creating open spaces near the river on its roof. In the remaining sections, the former wharfages – the so-called low pier, which lies immediately adjacent to the water at the foot of a high riverbank wall – were transformed into a promenade with playgrounds and sports fields, restaurants and an uninterrupted network of paths. As the Rhône has very short yet violent floods, there is the possibility that the new promenade will be completely flooded at times. The low pier is situated only just above the mean water level in some parts.

Sequences of riverside views The design theme of the riverside, which is in some places only 7 m and in other places up to 70 m wide, varies depending on the position and relationship to the town. From its extremes towards its centre, the promenade steadily becomes more urban and the variety of its possible uses increases. After each bridge that crosses the promenade the design changes so that near-natural riverside spaces alternate with both paved and multifunctional sections and almost garden-like riverside sections.

On the northern edge, an urban natural landscape has developed in front of the riverbank walls. Here, shallow beaches and small islands have emerged which, due to their location on a slip-off slope of the Rhône with decelerated flow, have not been stabilised and extend into the river. Beavers have settled here quite close to the town. The near-natural riverbanks in front of the promenade are still accessible: here, the planners have created a microtopography. Meandering ditches, which fill up to different levels, run through riparian woodland. The riverside thus has the appearance of a beach, but with only small fluctuations in water level, it turns into a series of islands. Silting and erosion processes in the river have formed sandy beaches in the upper reaches of the Rhône, which have in turn inspired the elliptic shape of the elaborately planted garden islands in the next section. At the end of this stretch of the promenade, the islands of plants on the otherwise predominantly paved low pier open into elongated ribbons of meadows planted with ornamental grasses.

1 Different path surfaces and the strip-like plantings [A5.8] structure the new promenade at the Rhône on the former low pier [A5.4]. 2 Schematic section of the northernmost part of the riverside, with sandbanks in front of the riverbank wall. 3 Schematic section of the part of the promenade where houseboats can be moored 4 A playground uses the difference in level at the riverbank wall [A5.6]. Equipment and benches are flood-resistant [A5.7]. 5 The near-natural sandy banks on the slip-off slope of the Rhône [D3.∂] in front of the embankment path. 6 New wooden surfaces serve as additional terraces for the restaurant boats [A6.3].

Dynamic River Landscapes

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Project Catalogue Dynamic River Landscapes

Isar, Munich

Isar Isar-Plan, since 2000 Munich, Germany River data for project area Stream type: Large rivers in the alpine foothills Catchment area: 2814 km2 Mean discharge (MQ): 64 m3/s One-in-100-year flood discharge (HQ100): 1050 m3/s Width of riverbed: 50–60 m; Width of flood plain: 150 m Location: 48° 06’ 35’’ N – 11° 33’ 35’’ E ∫ Design tools – – – – – – – – B3.∂ Invisible stabilisation C∂.4 Reprofiling the flood plain D∂.2 Dead wood D5.∂ Fish passes E∂.∂ Removing riverbank and riverbed

reinforcement

E∂.3 Regulating water extraction E2.∂ Reprofiling the channel cross-section E2.2 Introducing disruptive elements E2.3 Adding bed load E3.3 Creating multiple channels E4.∂ ‘Sleeping‘ riverbank reinforcement

260 26∂

Project Catalogue Dynamic River Landscapes

As early as the middle of the 19th century the Isar was canalised and straightened. The ‘torrential water’, as the Celts called the river, was steadily altered as its riverbanks were reinforced, its forelands closely mown, and the flow rate restricted with low weirs, thus preventing fish from migrating and sediment from being transported. In addition, in the south of Munich nearly all of the water in the river was diverted into a parallel canal in order to generate electricity. Only about 5 m3/s continued to flow within the tight profile, little more than a rivulet. As negotiations about the establishment of a new residual flow in this section of the river began, a discussion about the conversion of the Isar was also set in motion. Today 15 m3/s flow through the actual riverbed. The Isar is a gravel-dominated river in the alpine foothills prone to violent and sometimes sudden floods. The project area of the so-called Isar-Plan begins upstream of the city proper and stretches over 8 km to the centrally located Museum Island. The plan is a joint project of the City of Munich and the Free State of Bavaria, represented by the Munich Water Authority. The intent of the Isar-Plan is to increase contact with nature, improve flood management and offer more activities for rest and relaxation. Broadening the average width of the river from 50 m to up to 90 m was ecologically prudent and also increased the discharge cross-section. Due to this broadening, the height of the existing dikes did not have to be increased and the existing trees on them could be preserved. The dikes were stabilised, however, by adding an underground wall construction to their cores.

A wild river with dynamic boundaries

In terms of improving the quality of the river, the concept will promote the development of large-scale morphodynamic processes within clearly defined boundaries. In this way the river can, within specific limits, develop its own course within the flood plain. In order to restore some of the Isar’s original momentum, it was important to free the river of its canal-like corset: The trapezoidal profile made of stones and concrete was broken up and other protective measures removed. In order to protect the dikes ‘sleeping’ bank reinforcements were put in place, i.e., underground layers of stones that prevent the areas behind them from eroding. The river’s gravelly banks are subject to continuous change and are used by Munich’s residents as a large urban beach in the summer. It’s the perfect place for bathing, barbecuing, sunbathing and for ballgames. It’s also a perfect place for small children, who can splash around in the shallow water, for dogs, and even for people on horseback. The long gravel beach is only interrupted near the various bridges that cross the river. In these locations the riverbank needs to be sealed and the gravel is replaced by stone steps or walls. At the steps it’s possible to see just how much the river’s level fluctuates. The steps also create an interesting contrast to the wild gravel banks and are used as waterside seating areas.

1 Steps secure critical bottlenecks and make the entire riverbank usable [E4.3]. 2 Schematic section: The location of the ‘sleeping’ reinforcement is clearly visible [E4.∂]. Dikes were stabilised by using a concrete core [B3.1]. 3 In the redesigned sections flat and constantly changing gravel beaches, like here at the Flaucher, have replaced steep grass-covered slopes. 4 Dead wood structures are held in place by foundations and initiate new processes of erosion and sedimentation. They are also very popular with playing children [D∂.2]. 5 The amount of water diverted into another branch of the river to produce energy has been reduced [E∂.3].

A learning process The floods in 2005 caused erosion damage beyond what had been planned for, and in doing so provided information about how the flood management strategy should be adapted. As there is no planned or paved network of paths near the edge of the riverbank, a rough trail running directly on top of the ‘sleeping’ bank reinforcement was created, which has destroyed the protective grass cover. Barriers have now been put in place to prevent people from using the trail. In some places the ‘sleeping’ reinforcement has even been washed out. And while in some areas this condition has been allowed to persist, the river will continue to be carefully monitored. In this way, the conversion of the river can be seen as a learning process.

River. Space. Design.

River. Space. Design. Planning Strategies, Methods and Projects for Urban Rivers Martin Prominski Antje Stokman Susanne Zeller Daniel Stimberg Hinnerk Voermanek