General National Id Germany 02 light Site name Polder Altenheim Summary Ecological flooding has been introduced in a polder area next to the Rhine, near Altenheim in Germany. This measure improved the ecological functionality of the area, and created at the same time valuable space for recreation. Issues of forest management, a rising groundwater level and an increased mosquito population had to be dealt with. Light or indepth? Light NUTS Code Freiburg RBD code DE2000 Transboundary 0 Data provider Sabine Tutte, ACTeon Source(s) Auswirkungen der ökologischen Flutungen der Polder Altenheim The Integrated Rhine Programme, flood control and restoration of former floodplains along the upper rhine Integrated Rhine Programme Baden Wurtemberg NWRM(s) implemented in the case study Floodplain restoration and management Restoration and reconnection of seasonal streams Reconnection of oxbow lakes and similar features Forest riparian buffers Re-naturalisation of polder areas Longitude 7.809403 Latitude 48.464318 Site information Climate zone cool temperate dry Mean rainfall 800 Mean rainfall unit mm/year Average temperature 9,5 Mean runoff 1060 Mean runoff unit 600 - 750 mm Type Actual Test Site Average slope range 0-1% Monitoring maintenance Monitoring impacts effects 1 Monitoring location In-Stream Administrative annual costs 100000 Administrative annual cost information The Regional Council hopes that this number will decrease sooner or later due to new knowledge. Monitoring parameters Inside the polder several parameters were monitored to document the impact of ecological flooding on water and matter balance, state of groundwater, water courses and lakes, soil and biodiversity. Moreover, the water retention during flood events was documented. Performance Performance impact estimation method Catchment outlet Performance impact estimation information The amount of terrestrial plants and the domination of single species in different vegetation layers was determined by rough assuming. Aquatic macrophytes were documented by the estimation method of Kohler and Janauer. Beetles were counted by pitfalls, the diversity of birds was determined by observing and counting nests. Design & implementations Application scale Field Scale Installation date 1987 Age 27 Performance timescale Immediate Area (ha) 520 Area subject to Land use change or Management/Practice change (ha) 520 Design capacity description 17.6 Mio m³ Basis of design Use for retention approx. every 10 years. Inflow volume 40 Inflow volume unit m3/sec Peak flow rate 150 Public consultation 1 Design contractual arrangement Arrangement type Responsibility Role Comments Name Contractual agreement Responsible Treaty between France and Germany allowing France using the Rhine for Hydropower. Due to the construction of numerous dams the Rhine lost 90% of its floodplain and made the integrated rhine programme necessary Treaty of Versailles Organisational arrangement Supporting The riparian countries of the Rhine formed this comission to improve the water quality and the overall ecological state of the river. Navigability is moreover an important issue Comission for the Protection of The Rhine Design consultation activity Activity stage Key issues Name Comments Implementation phase Information evenings Since the ecological flooding is a quite new concept publicity has to be done in order that neighboring communities accept it. This has to be done continously. The polder Altenheim is a good exemple that shall calm down the worries of other communities were a polder shall be constructed Other site visits Design land use change Land use change type Design authority Authority type Role Responsibility Name Comments Other Determination of design details of the measure Regional Council Freiburg The Regional Council Freiburg is a sub division of the Ministry of the Environment in Baden Wurtemberg. It was in charge of the planning and design of the measures, as well as of the publicity Other Other District Council Approval of the measures Other Other Community of Neuried Member of the Mosquito fighting task force Forest owners Other Forest owners Needed planning reliability and supported therefore the ecological flooding approach NGO Initiation of the measure Environmental NGOs Supporter of the ecological flooding approach Lessons, risks, implications... Key lessons It is possible to adapt and modify the ecosystem inside a polder to water retention events by ecological flooding. Due to the measures the polder became a valuable recreational area for the citizens of the neighboring community. However, expensive protection measures for Altenheim are needed to avoid damage by rising groundwater level in consequence of ecological flooding. Financing mechanism 1 Financing mechanism information Land owners receive 20% of the value of their lot as compensation. In return, the regional council enters the title register in order to ensure that the lot can be used for flood protection even when the owner changes. Forest owners receive once a compensation. It would be difficult to discuss after every flood which damages on trees are recent or old. Since damages on fields happen only in the vegetation period, experts estimate after every inundation the damage. Afterwards the farmers are compensated. Financing difficulties 0 Success factor(s) Success factor type Success factor role Comments Attitude of decision makers main factor Financing possibilities main factor Attitude of relevant stakeholders secondary factor Financing Financing type Comments National funds 0.415 Sub-national funds 0.585 Barrier Barrier type Barrier role Comments Legal obligations / restrictions main barrier Ecological flooding does not reach the entire polder area. The good functioning of hydropower plants has priority. As a consequence, the flooding process depends on the Rhine discharge. Other secondary barrier During ecological flooding, humans have to be kept out of the area and its surroundings. During the first test ecological flooding, animals could not escape from the polder area, as they were scared by the humans which were watching on the dykes. Many deers drowned in the flood that was hyped by German tabloids as scandal. The principle and usefulness of ecological flooding is often not understood by citizens. On other planned retention areas (polder Schwanau) of the Integrated Rhine Programme communities went to court against the state of Baden Wurtemberg. They fear for example that rising groundwater levels could damage their houses, or that dirty Rhine water could affect the drinking water aquifer. Driver Driver type Driver role Comments Legal obligations main driver A sudden inondation of the polder would have caused a severe impact on the ecosystem. According to law, impacts have to be avoided, minimised or balanced. This led to the development of the ecological flooding concept. Legal obligations secondary driver Determines the amount of ecological flooding depending on the Rhine discharge. Financing share Financing share type Share Comments National funds 100 100% see above. 41,5% provided by the Federal Republic of Germany and 58,5% payed by the state of Baden-Württemberg. The total costs of the IRP are 1,3 billion €. View Policy, general governance and design targets Policy description Physical alteration of the channel, the river bed and the floodplain due to hydropower plants, flood protection and an easier navigability on the Rhine. Part of wider plan 1 Policy target Target purpose Increase Water Storage Peak-flow reduction Improved Biodiversity Policy pressure Pressure directive Relevant pressure Policy area Policy area type Policy area focus Name Comments Policy impact Impact directive Relevant impact Policy wider plan Wider plan type Wider plan focus Name Comments Integrated Rhine Programme The main focus of this programme is flood protection by restoring the floodplain on the upper Rhine upstream of Karlsruhe. Policy requirement directive Requirement directive Specification Socio-economic Direct benefits information Lease of land around the swimming lake. Ancillary benefits information Recreational value since the polder area is used for hiking, jogging, cycling and canoeing. Costs investment information The adaptation of the forest was "cost neutral" since the community of Altenheim used the money received by the state as compensation to place funds and the interests are invested into forestry. Costs capital 1300000000 Costs capital information This money had to be invested for the 13 retention areas of the Integrated Rhine Programme. Costs operation maintenance 450000 Costs operation maintenance Upkeeping costs per retention area. This depends on the length of the dykes, the number of pumping stations, the length of streets inside the polder etc. Costs total 700000 Compensations annual information Every landowner inside the polder receives 20% of the land value as compensation. In return the Regional Council Freiburg enters to the title register. Forest owners are compensated once, since it is too complex to discuss after every flooding whether damages are new or old. After flooding events experts assume the damage happen on fields and the farmers are compensated individually Ecosystem improved biodiversity 1 Information on Ecosystem improved biodiversity Due to ecological flooding alluvial plant and animal communities could be established. The floods diversify the water courses which thus became habitat of different invertebrate and fish species. Several groundbeetle and dragonfly species came back to the new established alluvial forest. However, the regular flood events are source of mosquito pests that require a treatment by the members of a taskforce. Ecosystem provisioning services 0 Ecosystem impact climate regulation No information available Biophysical impacts Information on increased water storage The water is stored in watercourses inside the polder and in case of retention also in the forest. Information on runoff reduction No data available. Information on Peak flow rate reduction During the last flood on the Upper Rhine in the 90's, the water retention inside the polder led to a reduction of the gauge of 24 cm and avoided thus the inondation of important industrial cities (Karlsruhe, Speyer, Mannheim). Information on Increased groundwater level Ecological Flooding leads to rising groundwater levels outisde the polder that can affect property. Therfore a complex drainage system including channels, wells,lakes and pumping stations was created. Information on Restoring hydraulic connections In order to distribute evenly water inside the polder, a system of water courses was reconnected and restored, the so called Schluten Water quality overall improvements Negative impact-WQ deterioration Information on Water quality overall improvements Measurements have shown that the overall water quality of the Rhine deteriorates when the water passes the polder. However, no danger for the drinking water supply exists. Soil quality overall soil improvements Positive impact-SQ improvement Information on Soil quality overall soil improvements Due to ecological flooding, the forest soil is constantly enriched by organic sediments serving as fertilizer for the plants. 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