APPROACH TO THE SPANISH WATER ORGANISATION IMPROVING FLOOD HAZARD MAPPING, LAWS AND AUTHORITIES COORDINATION

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1 "Workshop On Land Use Planning And Water Management, With Focus On Flood Risk Management Oslo, Norway. Wednesday 31 January and Thursday 1 February 2007 APPROACH TO THE SPANISH WATER ORGANISATION IMPROVING FLOOD HAZARD MAPPING, LAWS AND AUTHORITIES COORDINATION Speaker Javier Lastra Northern Spain Water State Corporation Environmental Government Department Member of the Spanish Working Group F on Flood jlastra@acunor.es

2 APPROACH TO THE SPANISH WATER ORGANISATION IMPROVING FLOOD HAZARD MAPPING, LAWS AND AUTHORITIES COORDINATION What are we talking about? - Rise of urban pressure on floodplains and exposure to flooding - Wrong response: usual unsuitable structural initiatives - Types of floods: Mediterranean ephemeral streams & mountain torrents - Floodplains retain flood potentially - Legal amendments (a protected space for the river, new definitions) - National system for flood hazard mapping - Approach to the Spanish water organisation. Authorities coordination

3 Urban pressure Since 30 years ago, a rise of settlements in floodplains has been produced, causing an increase of exposure to flooding. TRADITIONAL SETTLEMENTS IN NO FLOODING AREAS Years Years 2000 URBAN PRESSURE IN THE FLOODPLAINS INCREASE OF FLOODING PROBLEMS FIND SOLUTIONS

4 WRONG DESIGN Caused by using exclusively hydrological criterion, avoiding geomorphological analysis, historical data recopilation or sediment load consideration. SENSE OF FALSE SECURITY Structural initiatives that lack of necessary protection level. Wrong response Quinzanas meander Asturias Channelization September 1993 LACK OF STRUCTURAL MAINTENANCE Non estructural initiatives are more sustainable in the long term. Good Practices Document (WD, Athens, June 2003) This structural initiative increase flood hazard (lack of geomorphological analysis and maintenance) Flooding December 1993

5 Wrong response Wrong design Conflictive sites

6 Types of floods - Directive. Whereas 9. [ ] different types of floods occur, such as river floods, flash floods, urban floods and floods from the sea in coastal areas. [ ] - Directive. Article 2. "flood" definition [ ] shall include floods from rivers, mountain torrents, Mediterranean ephemeral water courses [ ] The Mediterranean ephemeral streams are gravel-bed fluvial systems that are usually dry most part of the year. The typical flood events in these currents are a combination of the basin physical characteristics of these areas (steep slopes, sparse vegetation, thin soils and permeable rocks), and intense, heavy and irregularly distributed rain. Runoff generation is sudden, resulting in a flash flood with sharp, narrow hydrographs with short time lags. FIGURE S SOURCE: Flood events in Mediterranean ephemeral streams (ramblas) in Valencia region, Spain. A.M. Camarasa Belmonte, F. Segura Beltrán. Catena 45(2001)

7 Types of floods The mountain torrents refers to the debris and mud flows, landslides and floodwater that happened in mountainous area caused by heavy rainfall. GRAO, 1921 VILLAMOREY (SOBRESCOBIO) ASTURIAS CANGAS DE ONÍS, ASTURIAS December 1996 The technical analysis about Mediterranean ephemeral streams and mountain torrents floods is quite different to the typical Europeans rivers, because the amount of sediment load is very high and the processes of erosion causes morphological and river path changes. The classic engineering approach based on water and transport sediment equations results weak without taking into account geomorphological and sedimentological studies.

8 Types of floods The effects of this kind of floods are impressive. These are some examples occurred in Spain: in 1957 a 2,500 m 3 /s flow of the River Turia (Valencia) killed 86 people; in 1962 a 1,200 m 3 /s in the Riera de Rubí dry bed (Barcelona) killed 973 people; in 1982 a convective storm with 300 mm precipitation in a single day caused the collapse of the Tous Dam (Valencia) resulting in a flood peak of 15,200 m 3 /s killing 38 people; in 1995 a storm produced flash flood killing 10 people in Yebra (Tagus basin). in people dead in Biescas s campsite by a mountain torrent caused by a 160l rainfall in 1 hour that carried tonnes of sediments in a 500 m 3 /s flood. BIESCAS, 1996 IMPROVING FLOOD HAZARD MAPPING, RIERA DE RUBÍ, 1962

9 Key issue! Floodplains retain flood potentially Removing floodplains suppose the reduction of areas with a high potential to retain flood water and sediment transported load. It contributes to aggravate flood damages. Directive. Article 7.3. Flood risk management plans shall take into account relevant aspects such as costs and benefits, flood extent and flood conveyance routes and areas which have the potential to retain flood water, the environmental objectives of Article 4 of Directive 2000/60/EC, soil and water management, spatial planning, land use, nature conservation, navigation and port infrastructure. AVILÉS Sediment trasported load IMPROVING FLOOD HAZARD MAPPING, ESVA RIVER room for the river Floodplain retains sediment

10 Legal amendments - A protected space for the river - To obtain the aims of preserving the good state of the water mass and preserve the role of floodplains in the lamination of water and sediments, the areas where the flow is essentially concentrated will be protected. Only will be authorized in this area the non-vulnerable activities that will not reduce the outflow capacity. Room for the river

11 Legal amendments - A protected space for the river - Floodplain limit Water rise Frequent flood Occasional flood Alluvial fans Torrential fans

12 Legal amendments - A protected space for the river - Main channel Very frequent flood Frequent flood Occasional flood Exceptional flood Bridge (light channel affec.) Bridge (mild channel affec.) Bridge (severe channel affec.) Artificial narrowing Piping under infrastructure Overflowing zone Water jump Dangerous junction Detail of a flood hazard map - Zonification -

13 Legal amendments - A protected space for the river - Very high-hazard flood area High velocity and depth High-hazard flood area Moderate velocity and depth Study area limit Land use restrictions Detail of a flood hazard map - Flow Velocity and depth analysis -

14 National system for flood hazard mapping The river basin districts from national administration will develop a National System for Flood Hazard Mapping in collaboration with the regional units of management. This system will include a detailed topographical analysis (LIDAR?), historical records and geomorphological-hydrological-hydraulic analysis. These maps will delimitate the public watercourse and the protected areas, including the areas where the flow is essentially concentrated. Historical records Geomorphological analysis Secundary channels Erosive evidences Interpretation & Zonation

15 Legal amendments - Improving definitions - Why definitions must be improved? Present definitions were defined from an hydrological point of view only. New definitions try to contribute also the geomorphological and ecological point of view. Watercourse definition [additions] The natural watercourse of a continuous or discontinuous flow is the area covered by water in the maximum ordinary rise. This area must be decided on the base of the geomorphological and ecological characteristics and taking into account the availability of historical data, photographic or cartographic. Flooding area definition [additions] A flooded area is considered when flooding of a terrain occurs during non-ordinary rise of lakes, reservoirs, rivers or streams and when it is suitable for retention of flow or solid transported load during rises.

16 Coordinated management Participative and coordinated management between authorities is needed to design the best solutions and not to fall into contradictory initiatives. Developing of a management directive must involve flood control, land use planning, fluvial and riparian systems restoration and water management. Key issue! The distribution of competent authorities in Spain for flood management in Spain involves mainly to: River basin districts Regional and local units of management Civil protection National administration Regional administration Regional and local administration National administration Regional administration To administer and to control the public hydraulic domain Land use management Emergencies management

17 Coordinated management The river basin districts must inform to the land use planning competent authority about the available studies and data related with flooding. This information must be taken into account for land use management, especially for the authorizations of nonvulnerable activities in flooding areas. River basin districts Regional unit managements