Final studies project RESEARCH mention - FLOOD RISK CULTURE : FROM USE TO DESIGN

FINAL STUDIES PROJECT - RESEARCH MENTION

THEME: ARCHITECTURE AND URBAN PLANNING

GWENDOLINE CHARREAU

2022-23

RISQUE : Le premier risque d’inondation en Ile-de-France est celui des crues de la rivière La Seine. C’est le euve le plus important de la région autour duquel est notamment le plus gros rassemblement démographique de France.

DIAGNOSTIQUE : En Ile-de-France, l'eau est une ressource indispensable aux activités humaines, elle participe aussi à la structuration du paysage. De nos jours, les dégâts des eaux comptent parmi les risques naturels les plus dommageables et sont susceptibles de devenir plus fréquents, plus pertinents et plus douloureux à l'avenir en raison des e ets de l'augmentation de la population et de l'impact du changement climatique. CATALOGUE ET

VULNERABILITÉS : Il existe beaucoup de vulnérabilité sur le territoire de la région Ile-de-France, mais les trois principales qui ont déterminé cette recherche sont : la densité de population, les territoires fréquemment inondés et la vulnérabilité sociale des riverains.

ENJEUX : L’Ile-de-France, et surtout Paris avec ces communes proches, sont à fortes enjeux démographique, économique et patrimoniale.

FLOOD RISK CULTURE : FROM USE TO DESIGN

STRATÉGIE : Proposer un aménagement résilient aux inondations d’une communauté en bord de Seine. Le projet prendra pour language paysager, architectural et urbain les usages des riverains.

ENSA-VERSAILLES

TEACHERS:

INGRID TAILLANDIER : DPLG - DIRECTOR OF THE FRENCH/CHINESE MASTER IN URBAN PLANNING

EMILIE GASCON : TEACHER RESEARCHER - PHD - URBAN ARCHITECTURAL DESIGN

USAGE DE LA COMMUNAUTÉ

RIVERAINS & EXPERTS

SCALE OF REFLECTION

TERRITORY & FLOOD

FLOOD : MORE THAN JUST WATER

A flood is an overflow of water usually submerging dry land. Floods can be classified into 6 types: river floods, coastal floods, reservoir/dam floods, sewer floods, groundwater floods and surface water floods.

When researching about floods, it is important to understand their multiplicity. Indeed, different types of floods can occur at the same time. Of all these types of water overflow, there is only one really addressed in this PFE research: river flooding.

The submersion of the land at the time of the flood is not the only element of this natural crisis, indeed, the floods are part of a more complexe cycle.

PREVENTION& MITIGATION

Redraw in 2022 from data: The risk management cycleAtkinson et al, 2006

Pourcentage d’occurrences de catastrophes naturelles par type de catastrophe (1995-2015) - Dans le rapport “The Human Cost of Weather Related Disasters” du Centre de recherche sur l’épidémiologie des catastrophes (Centre for Research on the Epidemiology of Disasters) - 2017

WATER: RESOURCE & DANGER

Water is an essential resource for human and economic activities. It structure landscapes, is an ecosystem, has shaped our environment through it and still shapes it.

Obviously, water is also, and has always been, a risk factor, especially flooding. However, civilizations have been built around water, because it is a vital asset for life, despite floods.

Water damage is one of the most damaging natural hazards today and is likely to become more frequent, more relevant and more important in the future due to the effects of increasing population and the impact of climate change.

Australian Government - bureau of meteorology - Article - Explainer: what is a flood? - 04 July 2019

FLOOD RISK MANAGEMENT

Île-de-France region flood risk management strategy is mainly focused on retention basins, some of which date back to the 1970s. However, this is not the only solution and through a state of the art study of flood risk management, we can determine on a large scale 6 types of devices:

1.1 MITIGATE

Use natural or man-made structures and spaces to reduce water velocity and/or turbidity. This increases the time it takes for a given volume of water to move along the track and provides an increased opportunity for infiltration.

1.3 CREATION

Construct or generate new landforms/structures in or near water bodies on which development and/or alternative land uses may be assigned.

1.5 REALIGN

Reduce exposure to flood risk by repositioning the receptor (e.g. community, critical infrastructure, property) or changing land use classification.

1.2 RESISTANCE

To reduce a community’s exposure to flood risk by preventing water ingress through the use of flood risk management measures.

1.4 RELIEVING

Increase the capacity of a water supply system (o provide additional floodable areas?) to reduce peak flood levels and limit the extent to which vulnerable locations are at risk of flooding.

1.6 TO LIVE WITH

Use flood-resilient design to organize the built and natural environment. A range of spatial tactics can be applied depending on a particular context, scale or timescale to the presence of water.

Data : Rettrofitting for flood resilience - A guide to building and community design - RIBA -2022

RESISTANCE OR RESILIENCE : SOFT & HARD ADAPTATION

The concept of “resilience” attributed to floods questions the way of thinking about urban planning and its ability to adapt to disturbances. Resilience as a word has many definitions. However, for this study, flood resilience is the improvement of the built environment and the rapid recovery of its community after such floods.

It’s a whole new experience that continues a trend of “living with water” that began about 50 years ago. Even though the word “resilience” comes from the Latin word “resilire, resilio”, meaning “to bounce back”, it will only be used here as a new tool / a new philosophy of flood risk management.

Traditionally, society at risk has tended to adopt a resistance-based strategy of resistance, also known as “hard” flood defenses. Historically, cities took refuge behind their walls to counter the risk of looting during wars. The same was true for natural hazards. From then on, the flood walls became levees. The construction of these resistance / “hard adaptation” strategies and equipment poses two major problems.

The socioeconomic state in dry condition

The socioeconomic state in dry condition

Floods

Floods preventable Flood magnitude

Floods beyond the threshold create desasters and move the system out of the desirable regime

Floods beyond the threshold create desasters and move the system out of the desirable regime

The socioeconomic state in dry condition

Floods pre-

Floods beyond the threshold create desasters and move the system out of the desirable regime

Floods beyond the threshold create desasters and move the system out of the desirable regime

Redraw in 2022 from reference : The risk management cycle - Atkinson et al, 2006

ILE-DE-FRANCE RISK = HAZARDS x VULNERABILITIES x EXPOSURE

The risk can be calculated simply by adding the hazards zones, the exposure and the vulnerabilities. The greatest benefits can be obtained by reducing vulnerability to natural hazards.

The vulnerability analysis of the region points to the center of Ile-de-France region.

To deepen the study, Kenji Fujiki’s work, “Prospective study of the social impacts of a major flood in the Ile-de-France region” has been added as social vulnerability.

Ile-de-France region: hydrographic network

EXPOSURE HAZARDS

The most vulnerable area in terms of flood risk in the Ilede-France region. There are 4 departments: Paris, Haut-deSeine, Val-de-Marne, SeineSaint-Denis.

VULNERABILITY

REFERENCES QGIS :

1- DRIEE-shapefile - 2020

2- Data.gouv Limites

Départementales et communales - 2022

3- Découpe morphologique d’Ile-de-France - Data.

gouv.fr - 2016

4- Corine Land Cover2021

5- Data.gouv.fr, Enjeu écoonomique, patrimoine et mobilité - 2013

SOCIAL VULNERABILITIES

Areas most affected by floods and social inequalities

Combinaison de l’indice SVEAI et de l’indice de risque géophysique à l’échelle du TRI « Métropole francilienne » (Données : DRIEE, IGN, INSEE). - Page 114 de :

Prospective study of the social impacts of a major flood in the Ile-de-France region

Etude prospective des impacts sociaux d’une inondation majeure en régionIle-de-France. Disparités socio-spatiales dans la prise en charge des populations franciliennes ensituation de crise et post-crise : une analyse cartographiée et quantifiée des besoins des ménages, de l’évacuation à la reconstruction.

Thèse de DOCTORAT DE L’UNIVERSITE DE LYON opérée au sein de l’Université Jean Moulin Lyon 3

Ecole Doctorale N° 483

Sciences Sociales

Discipline de doctorat : Géographie – Aménagement

SCALE OF REFLECTION

UPSTREAM SEINE

The most interesting area to research several case studies seems to be in the southern suburbs of Paris. In the department of Val-de-Marne (94), in the upstream area of the river La Seine.

The Communes (municipalities) along the Seine and part of the department of Val-de-Marne, are 9 in total.

All these 9 municipalities have part of their territory in a flood zone. For some of them, the flood return period of the Seine varies between 2 to 10 years. Which was not the case 20 years ago. In these municipalities, resilient flood risk management is an essential strategy.

While looking closely, one town in particular seems to stand out: Villeneuve-Saint-Georges.

Scale of study : Upstream

TERRITORY ANALYSIS

VILLENEUVESAINT-GEORGES MUNICIPALITY

MUNICIPALITY IN DANGER

This municipality is the most flood-prone because of its exposure to the overflows of the Seine and the Yerres rivers.

The rise in water is generally slow for the Seine but can take 3 to 4 weeks to leave.

The Belleplace-Blandin neighborhood is particularly impacted by the overflows of the Yerres while the Seine river floods the Villeneuve-Triage neighborhoods.

Those neighborhoods were the most damaged areas during the floods of June 2016, January 2018 and 2021, causing significant damage and requiring numerous evacuation operations.

Avenue de Choisy - Photo : Le Figaro - Inondation 2016

TRIAGE NEIGHBORHOOD

ABANDONED TERRITORY

Following the increase in the return of flood periods, areas in Villeneuve-Saint-Georges such as the BelleplaceBlandin district on the banks of the Yerres and the Triage district on the Seine, are gradually being abandoned.

Indeed, the increasingly numerous and close evacuations, as well as the cost of repairs, are pushing many to sell or abandon their place of residence. An increasingly pronounced desertification is thus observed in these areas.

The fate of the district on the Yerres is already to relocate all the inhabitants and leave the place to the water. However, the Triage district could present a new face in the face of flooding and allow residents to live with the water without moving.

To improve the living conditions of local residents, it would therefore be necessary to:

1- Ensure a good quality of life on site during floods and avoid evacuation at all costs;

2- Ensure the resilience of structures and equipment;

3- If evacuation is necessary, ensure that it goes smoothly.

Villeneuve-Saint-Georges Triage : Aléas d'inondation

HAZARD RISK MAP OF TRIAGE NEIGHBORHOOD

RISK CULTURE

MISUNDERSTOOD RESILIENCES & RESISTANCE OF THE INHABITANTS

In view of the existing and future challenges, whether human, economic, social or environmental, it is necessary to reduce vulnerabilities and improve the resilience of territories.

But how? There are many axes in the risk management policy, including the risk culture.

However, for this project, the axis of study allows us to note a resistance in the face of resilience, in particular through the study of residents’ uses.

Indeed, the residents of Triage have their own measures to deal with floods and sometimes these even go against the principles of resilience despite the arrangements made in this direction.

Permeable pavers filled in due to lack of risk culture

Edge of the Seine - Pavers nomore permeable - Triage - Villeneuve Saint GeorgesApril 2022 - Photo: G.C.

GESTION DES RISQUES D’INONDATIONS : SOLUTIONS DE LA VILLE

GESTION DES RISQUES D’INONDATIONS : SOLUTIONS DES HABITANTS

FROM USE TO DESIGN

LOCAL RESIDENT USES

It has been proven that the flood prevention strategy with the culture of risk, as it is used at present, does not seem to work at best, despite the attempts of the State and the municipalities (1) .

To avoid a misunderstanding of the resilience mechanisms and the resistance of local residents, the problem can be reversed and the uses of said local residents can be made resilient.

The combinations of devices used on the previous page and the uses in the face of flooding help us to define a strategy.

Thus, uses can design the space to be more resilient.

(1) RAPPORTS - Service Prévention des risques et des nuisances - Bureau de la Planification du SGZDS - Décembre 2016 -

1: Use of a boat to travel during floods

2: Observation of a street not adapted to flooding and/or use by local residents during floods

3: Designing from uses and resilience