River space design second edition by Birkhäuser

Adding bed load ∆ Agriculture ∆ Art objects and relicts ∆ Attachable protection elements ∆ Backwaters ∆ Bank reinforcement as needed ∆ Bioengineered groynes ∆ Boulders and stepping stones ∆ Branches ∆ Broad riverbank steps ∆ Building over the existing reinforcement ∆ Buildings on piles ∆ Bypass culverts ∆ 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 ∆ Perceptible changes in fluvial patterns ∆ Piers and balconies ∆ 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 ∆ Stabilised wetland ∆ Stone revetment ∆ Submerged groynes ∆ Submergible boardwalks ∆ Submergible furniture ∆ Submergible planting ∆ Submergible riverside paths ∆ Superdikes ∆ Surmounting the embankment wall ∆ Suspended pathways ∆ Terraced gabion revetments ∆ 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. This book contains a comparative analysis of more than 60 successful projects alongside rivers and streams worldwide, 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. For this second and enlarged edition, 12 best-practice case studies mostly from North America and Asia and several design tools were added.

River. Space. Design. Second and Enlarged Edition

Planning Strategies, Methods and Projects for Urban Rivers Martin Prominski Antje Stokman Susanne Zeller Daniel Stimberg Hinnerk Voermanek Katarina Bajc

∂

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 ∆ 144 Process Space A Embankment Walls and Promenades ∆ 148 Allegheny River, Pittsburgh, USA 150 East River, New York, USA ∆ 152 Elster and Pleiße Millraces, Leipzig, Germany ∆ 156 Fox River, Green Bay, USA ∆ 160 Leine, Hanover, Germany ∆ 162 Limmat, Zurich, Switzerland (Factory by the Water) ∆ 164 Limmat, Zurich, Switzerland (Wipkingerpark) ∆ 166 Rhône, Lyon, France ∆ 168 Seine, Choisy-le-Roi, France ∆ 172 Spree, Berlin, Germany ∆ 174 Wupper, Wuppertal, Germany ∆ 176

Process Space B Dikes and Flood Walls ∆ 178 Elbe, Hamburg (Promenade Niederhafen), Germany ∆ 180 IJssel, Doesburg, the Netherlands ∆ 182 IJssel, Kampen, the Netherlands ∆ 184 Main, Miltenberg, Germany ∆ 188 Main, Wörth am Main, Germany ∆ 190 Nahe, Bad Kreuznach, Germany ∆ 194 Regen, Regensburg, Germany ∆ 198 Waal, between Afferden and Dreumel, the Netherlands ∆ 200 Waal, Zaltbommel, the Netherlands ∆ 202

Process Space C Flood Areas ∆ 204 Bergsche Maas, between Waalwijk and Geertruidenberg, the Netherlands ∆ 206 Besòs, Barcelona, Spain ∆ 208 Buffalo Bayou, Houston, USA ∆ 210 Ebro, Zaragoza, Spain ∆ 212 Elbe, Hamburg (HafenCity), Germany ∆ 216 Gallego, Zuera, Spain ∆ 218 Guadalupe River, San Jose, USA ∆ 222 Ihme, Hanover, Germany ∆ 226 IJssel, Zwolle, the Netherlands ∆ 228 Kyll, Trier, Germany ∆ 230 Maas, Maasbommel, the Netherlands ∆ 232 Petite Gironde, Coulaines, France ∆ 234 Rhine, Brühl, Germany ∆ 238 Rhine, Mannheim, Germany ∆ 240

Seine, Le Pecq, France ∆ 242 Waal, Gameren, the Netherlands ∆ 244 Wantij, Dordrecht, the Netherlands ∆ 248 Wupper, Müngsten, Germany ∆ 250 Yiwu and Wuyi Rivers, Jinhua, China ∆ 252 Yongning River, Taizhou, China ∆ 256

Process Space D Riverbeds and Currents ∆ 258 Ahna, Kassel, Germany ∆ 260 Alb, Karlsruhe, Germany ∆ 262 Birs, Basle, Switzerland ∆ 264 Kallang River, Bishan, Singapore ∆ 266 Leutschenbach, Zurich, Switzerland ∆ 270 Neckar, Ladenburg, Germany ∆ 272 Seille, Metz, France ∆ 276 Soestbach, Soest, Germany ∆ 278 Wiese, Basle, Switzerland ∆ 280 Wiese, Lörrach, Germany ∆ 282

Process Space E Dynamic River Landscapes ∆ 284 Aire, Geneva, Switzerland ∆ 286 Emscher, Dortmund, Germany ∆ 290 Isar, Munich, Germany ∆ 294 Losse, Kassel, Germany ∆ 298 Schunter, Braunschweig, Germany ∆ 300 Wahlebach, Kassel, Germany ∆ 302 Werse, Beckum, Germany ∆ 304

Appendix Project Credits and References ∆ 307 Further Reference Projects ∆ 315 Glossary ∆ 319 Selected Bibliography ∆ 322 Indices ∆ 325 Authors ∆ 331 Acknowledgements ∆ 331 Illustration Credits ∆ 332

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.∂ Piers and 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 relicts ∆ 85 B6.3 Perceptible changes in fluvial patterns ∆ XX

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

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

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∂

C∂.8 Bypass culverts ∆ XX

C2.∂ Mounds ∆ 97

D2.2 Extending the flow length ∆ ∂∂9

C2.2 Mound principle with buildings ∆ 97 C2.3 Buildings on piles ∆ 98

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

C2.4 Escape routes ∆ 98 C2.5 Cableways ∆ 99

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

Placing over the water ∆ 96

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 C3.9 Stabilised wetland ∆ ∂03 C3

Evading ∆ ∂04 C4.∂ Warning signs and barriers ∆ ∂05 C4.2 Electronic warning systems ∆ ∂05 C4

Adapting ∆ ∂06

D2 Grading the channel ∆ ∂∂8 D2.∂ Widening the channel ∆ ∂∂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

D4.7 Terraced gabion revetments ∆ ∂25 D5 Varying the riverbed reinforcement ∆ ∂26 D5.∂ Fish passes ∆ ∂27

C5.∂ Floating and amphibious houses ∆ ∂07

D5.2 Varying the riverbed and transverse structures ∆ ∂27

C5.2 Marinas ∆ ∂07

D5.3 Ramps and slides ∆ ∂27

44 45

Design Catalogue Introduction

C3 Tolerating

All design tools in C3 can be combined with – – – – – – – – C∂.∂ Setting back the dike C∂.2 Branches C∂.3 Flood channels C∂.4 Reprofiling the flood plain C∂.5 Backwaters C∂.6 Polder systems C∂.7 Retention basins C4.∂ Warning signs and barriers C4.2 Electronic warning systems

Amenities in the flood plain must be able to withstand the force of floodwater and tolerate temporary submersion. For most of the year, when rivers run at medium or low water levels, unlimited use of the flood area is possible. At high water level these places are no longer or only partially accessible. For this reason temporary uses must be found that can tolerate high water such as sports facilities, playgrounds and campsites, festival grounds or also quasi-natural areas with typical riparian vegetation. The facilities are permanently installed and the materials selected to be able to withstand longer flood periods. Elements that cannot resist flooding must be removed for storage elsewhere in case of a high water event. Permanently installed elements in the flood area may not obstruct floodwater discharge. At a larger scale, the type and location of the open spaces in the topography play an importatnt role in the design of flood areas. More complex, costly and high-maintenance areas such as sports facilities can be planned for higher-lying areas of the flood plain because these are flooded less frequently. Thus the facilities can be used for most of the year and need not be cleaned of sediment after flooding so often.

C3.∂

C3.2

C3.3

Paths within the flood plain

Sports facilities and playgrounds

Flood-tolerant buildings

Ebro, Zaragoza, embankment in the city centre

Gallego, Zuera, bullring

Elbe, Hamburg, Fish Auction Hall

Setting up a road and pathway concept involves zoning and differentiating between inaccessible, seldom used and frequently used areas of the flood plain. The path networks can be built as narrow footpaths or broad, surfaced access. Complex and costly boardwalk constructions, such as in Zaragoza on the River Ebro, dramatise the natural flood plain. Cleaning the path of deposits after flooding may be necessary depending on the sedimentation patterns of the river. Low dike lines within the flood plain that restrain less dramatic summer high water events are, because of their linear character and elevated position, well-suited for use as the foundations of pathways.

Sports and play facilities promote recreational uses of flood plain areas. They can be designed in very diverse ways, ranging from the use of a meadow for ball games through more complex sports grounds or golf courses through to exceptional uses like the bullring in Zuera in Spain, whose round arena is submerged by up to 1 m during high water events. At the waterside there are often playgrounds that, though they may not use the water directly, still enhance the water experience.

An appropriately adapted and equipped flood-tolerant building can be subjected to flooding without sustaining significant damage. This means, for example, tiled floors and walls and specially protected electrical installations. Traditionally, many buildings in flood areas such as the centre of Cologne or the Fish Auction Hall in Hamburg were adapted in this way; today these concepts are being discussed anew in the light of more stringent flood protection regulations. In Kampen on the River IJssel in the Netherlands, sections of the existing built area were not included in the new flood protection system due to their awkward locations and the buildings were equipped to be flood-tolerant instead. A tolerant attitude to flooding can reduce the costs and effort involved in building protection systems.

– – – – – – – – Ebro, Zaragoza Δ 212

– – – – – – – – Gallego, Zuera Δ 218 + Rhine, Düsseldorf, Lausward Golf Course Δ 317

Gallego, Zuera Δ 218 IJssel, Zwolle Δ 228

– – – – – – – –

Yiwu and Wuyi Rivers, Jinhua Δ 252

IJssel, Kampen Δ 184

+ Ebro, Zaragoza, Riverbank Improvements

+ Elbe, Hamburg, Fish Auction Hall Δ 315

in the City Centre Δ 315

100 101

Design Catalogue Flood Areas

Allegheny River Allegheny Riverfront Park, 1994–1998 Pittsburgh, USA River data for project area Catchment area: 30 000 km² Mean discharge (MQ): ~ 550 m³/s Width of riverbed: 220 m Location: 40° 26’ 41” N – 80° 00’ 08” W

Design tools – – – – – – – – A1.1 Intermediate levels A2.1 River access parallel to the bank A5.4 Submergible riverside paths A5.5 Submergible boardwalks and overhangs A5.7 Submergible furniture

Pittsburgh, Pennsylvania, developed rapidly as a result of industrialisation, and in spite of the plans of Frederick Law Olmsted Jr. for creating a park system adjacent to the riverside in 1911, subsequent years saw the riverbanks of the Allegheny River being filled with highways and dense urban fabric. Access to the river in the town centre was thus fully obstructed with the exception of the Point State Park at the river’s confluence with the Monongahela River. In 1984 the Pittsburgh Cultural Trust was created with the task of revitalising 14 neglected blocks in central Pittsburgh to the south of the Allegheny River and developing a new cultural district. Enhancing access to the Allegheny riverfront on this section and improving its urban quality was identified as an important aspect of the project’s overall success.

A5.8 Submergible planting A5.9 New embankment walls

150 151

Project Catalogue Embankment Walls and Promenades

A park on two levels

The site had many challenges, such as the 7 m difference in elevation between its two levels, its narrow longitudinal shape, periodical flooding and several highways dissecting the space on both levels. The park design was therefore divided in two sections, lower and upper, each with its own function and design language. The lower park was intended to offer direct contact to the river; however, it was extremely limited in terms of space, with a highway on one side and water on the other. To solve this issue, the designers proposed to cantilever the promenade to gain more space for the lower-level park. The overhang needed to be counterweighted by concrete slabs, which also serve as seating distributed along the edge of the promenade. The lower park is connected to the town above it via ramps linked to the iconic Andy Warhol Bridge in the middle of the site, named after this artist since he was a native of Pittsburgh. Ramps provide a soft transition between the different levels and effectively act as a barrier against noise from the highway. With their plantings of Virginia creeper (Parthenocissus quinque-

folia), they provide a green buffer for the site. The upper part of the park runs alongside the existing flood wall, which reaches a height of 7 m to protect the city and the upper park from flooding. The course of the adjacent highway was shifted to one side to enlarge the upper park, which is designed as an urban plaza with seating and spectacular views across the river.

Floodwater resilience The lower park level and the highway are completely inundated during flood events. Water typically rises 1 m during annual floods and occasionally up to 6 m, as in 2004. Accordingly, the lower level of the park is planted with native, successional, flood plain species typical of the upriver Allegheny banks, such as silver maple (Acer saccharinum), river birch (Betula nigra), red maple (Acer rubrum), cottonwood (Populus) and red bud (Cercis canadensis). Very young saplings were planted at the site enabling them to adapt gradually and thus increase their resilience to flood conditions. Species such as river birch were also chosen because of their ability to re-sprout if the trunk is damaged during a flood. Large bluestone boulders were brought to the site to evoke a wild, natural atmosphere. They provide protection for the trees during flood conditions by anchoring the root balls, slowing down the floodwaters, mitigating erosion and causing silt to be deposited.

1 The lower park promenade is situated on the overhang or cantilevers above the water. 2 Schematic cross-section showing the submergible overhang construction of the lower park, the highway and the upper park located on the edge of a wall 7 m above street level. 3 Access ramp to the park [A2.1]. An undulating bronze handrail custom-designed by the artist Ann Hamilton evokes the riverâ&#x20AC;&#x2122;s tactile aesthetics 4 The highway parallel to the ramp is submerged in the event of flooding. 5 The lower park encourages contact with the river and activities such as fishing and boating.

Fox River River Decks and Promenade ‘CityDeck’, 2012 Green Bay, USA River data for project area Catchment area: 16 650 km² Mean discharge: ~ 120 m³/s Width of riverbed: ~ 200 m Location: 44° 31 ‘01” N – 88° 00’ 56” W

Design tools – – – – – – – – A 4.1 Piers and balconies A 5.5 Submergible boardwalks and overhangs A 5.7 Submergible furniture A 6.1 Floating jetties

The Fox River floods regularly, so the riverbanks in Green Bay, Wisconsin, have been engineered and reinforced in the course of time. As in many other geographically similar towns, central Green Bay had turned its back on the river, as the edge of the water was no longer attractive, nor was it accessible due to the high bulkhead walls. The aim of the CityDeck project was to challenge this situation and revitalise the riverfront, creating a flexible space for gatherings, and thus increasing opportunities for social life. Reanimating the waterfront was also one of the development strategies for raising interest in adjacent, underused inner-city parcels of land. The CityDeck was the starting point for this multiphase redevelopment project. The site comprises a strip along the river less than 20 m wide.

B 2.1 Integrating flood protection walls

New waterfront boardwalk CityDeck

160 161

Project Catalogue Embankment Walls and Promenades

The project consists of a boardwalk deployed at the riverbanks, extending usable riverside space by constructing a wooden platform overhanging or floating on the water. The deck also spreads out over the existing steel bulkhead walls, which were built in six different sections over a long period of time, each time with a different structural system. The wooden platform hides those complex structures underneath. The ‘folds’ of the wooden deck also act as urban furniture in the shape of seats, benches and lounges and they extend further over the river as a boardwalk with shallow steps descending to the water. Attached floating piers and jetties for recreational boats provide another link between the city and river life previously missing. On the city side, the surface ‘folds’ again to protect adjacent buildings from flooding. Seating elements in this area conceal a rainwater infiltration zone and a low flood protection wall. The paving is of pervious material, allowing water to recede quickly after flood events and heavy rain. Both the robustly built wooden deck as well as the wooden furniture can tolerate occasional flooding and provide a varied leisure space in the dry season.

1 The CityDeck extends and activates a narrow public space between the river and the urban fabric. 2 Typical cross-section of the wooden deck, floating elements and outdoor furniture [A4.1, A6.1] 3 The system of floating and fixed promenades along the riverbank [A5.5] 4 In the event of flood, the deck and its outdoor furniture are temporarily submerged [A5.7]. 5 Outdoor furniture is integrated into the promenade and conceals the rainwater infiltration strip, flood protection elements and steel bulkhead walls underneath [B2.1]. 6 Access to the floating elements

Yiwu and Wuyi Rivers Yanweizhou Park, 2014 Jinhua, China River data for project area Catchment area: < 6000 km² Width of riverbed: Yiwu River 226 m; Wuyi River 173 m Location: 29° 05’ 35” N – 119° 39’ 58” E

Design tools – – – – – – – – A5.5 Submergible boardwalks and overhangs C1.4 Reprofiling the flood plain C2.3 Buildings on piles C3.1 Paths within the flood plain C3.4 Parks within the flood plain C3.5 Extensive natural areas C3.8 Events grounds D4.2 Living revetment

Jinhua City, Zhejiang Province, lies at the confluence of the Wuyi and Yiwu Rivers, where both meet to form the Jinhua River; here one finds the Yanweizhou wetland, covering 26 hectares. It is the last piece of natural riparian wetland to remain relatively intact in the urban fabric of Jinhua, although it has suffered from fragmentation, erosion and sand quarrying. A monsoon climate is characteristic of Jinhua, and the Yanweizhou riparian wetland is affected by annual monsoon flooding. The initial proposal made by Jinhua city officials to tackle these challenges was to protect the wetland against 20-year and 50-year floods by erecting high concrete retaining walls. These had already been applied to enhance flood protection and land reclamation elsewhere in the city; however, their cumulative effect worsened the destruction caused by the floods. Implementing the wall would also have had the effect of impeding water flow and the silt deposits that sustain and rejuvenate the lush wetland ecology. It would have further severed the connection between the riparian flood plains, the river and the city. Therefore, the designers opposed the idea and advocated demolishing the existing artificial floodwater infrastructure on that site.

The flooded landscape

252 253

Project Catalogue Flood Areas

Instead they proposed a terraced river embankment planted with native flood-tolerant vegetation to accommodate annual flooding. This was achieved by the cut-and-fill technique and by adapting the site to the earlier topographical interventions and pioneer vegetation which had emerged as a result of quarrying for sand. The secondary growth of poplar trees (Populus canadensis) and Chinese wingnut (Pterocarya stenoptera) was predominant in the existing wetland, providing a habitat for native birds such as egrets. This biodiversity was increased by additionally planting other native vegetation supportive of local wildlife. The terraces are reachable via steps and equipped with urban furniture and pavilions, which are submergible and not accessible

during floods. A riparian habitat with tall grasses on the terraces is rejuvenated by each such event, as the water irrigates the site and deposits fertile silts. Stormwater, which flows in the opposite direction from the park into the river, is filtered and purified when passing through wetland vegetation of the terraced river embankment. During flooding the inner lake also functions as a retention area which expands and eventually merges into the adjacent rivers. During the dry season the water from the rivers percolates through the gravel layers into the lake, undergoing filtering in the process. The lake thus provides cleaner and calmer water in a safer environment in comparison to the riverbanks. Therefore here, on the lake, one finds areas where people can come into direct contact with the water. The park is covered with a layer of permeable material and has a system of circular bio-swales to enhance stormwater infiltration.

1 The park extends across a flood plain at the confluence of the Wuyi and Yiwu Rivers. The area is well-connected to the city on both riverbanks via an extensive pedestrian network across the Bayong Qiao Bridge, which can be used even in times of flooding [C3.4]. The colourful bridge alludes to the Bench Dragon Dancing tradition and has become a landmark for the entire city. 2 The schematic cross-section shows the riparian bank and the terraced embankment, which is inundated during floods. 3 Another path system runs almost at water level to connect parts of the park across the water bodies [C3.1]. 4 Visitors are given several opportunities to come into contact with water at the lake in the heart of the park. The lake itself serves as a retention waterbody and is submerged during monsoon floods, thus reconnecting with the river. 5 The paths are covered with gravel and thus permeable. They lead to all parts of the park, including the terraced embankment, which is dense with native flood-tolerant vegetation.

Bayong Qiao Bridge Connectivity in the park is ensured by flood-adapted boardwalks, paths and ramps leading to the wetland area, which are submerged during 20-year flood events. An iconic new bridge meanders above the park for 700 m, linking it with the northern and southern districts of the town on both sides of the confluence, even when the park itself is submerged. It lies higher than the 200-year floodwater level, with ramps leading to various locations in the city. Powerful flood dynamics can be observed from above and remind people of the enormous strength of the bodies of water surrounding them. In the dry season it gives visitors the opportunity to observe the natural riparian habitat from above without disturbing it. The bridge has become an important landmark and a cultural asset for the city.

254 255

Project Catalogue Flood Areas

6 An aerial view of the park during the dry season 7 Vegetation was chosen due to its capacity for flood-resilience and planted to revitalise former sand quarries, which had degraded the landscape. 8 The native grasses display vivid colours throughout the year. 9 The iconic Bayong Qiao Bridge 10 An aerial view of the park during the monsoon season shows areas submerged during a 20year flood. 11 The concrete flood wall needed to be removed to build the terraced embankment. The cutand-fill earthmoving method meant that earth from the cut equalled the amount of fill. 12 Submergible boardwalks [A5.5] 13 A structure on piles overlooking the wetlands [C2.3]

River. Space. Design.

River. Space. Design. Second and Enlarged Edition

Planning Strategies, Methods and Projects for Urban Rivers Martin Prominski Antje Stokman Susanne Zeller Daniel Stimberg Hinnerk Voermanek Katarina Bajc