General National Id Denmark_01 Site name Odense river catchment Summary The Odense is a river in southern Denmark. It was channelized and deepened in the late 1940s to improve agriculture. The NWRM consists of a series of measures to restore floodplain connectivity along a 17 km section of the river. The measures will prevent flooding in downstream towns and cities. This will have a number of effects on the pressures relevant for the WFD. Reduced risk for flooding of urban environment reduces the risk for storm overflows from sewers as well as diffuse pollution resulting from flooding in general. Re-meandering reduces the pressure from previous physical alterations for flood protection and agricultural purposes. It will also potentially have a positive effect on ground water recharge in temporarily flooded areas. Light or indepth? In-depth The in-depth description of the case study cs-dk-01-final_version.pdf NUTS Code Syddanmark RBD code DK1 Transboundary 0 Data provider Mats Ivarsson, Enveco Source(s) Linking floodplain hydraulics and sedimentation patterns along arestored river channel: River Odense, Denmark Vandtillbageholdelse i vådområder: Odense Å case område Odense Å ved Brobyværk NWRM(s) implemented in the case study Wetland restoration and management Floodplain restoration and management Re-meandering Riverbed material renaturalization Longitude 10.2824 Latitude 55.2196 Site information Climate zone cool temperate moist Mean rainfall 727 Mean rainfall unit mm/year Average temperature 8,19999980926514 Mean runoff 316 Mean runoff unit 450 - 600 mm Average runoff coefficient 0,430000007152557 Type Actual Test Site Monitoring maintenance Monitoring impacts effects 1 Performance Performance impact estimation method Laboratory Performance impact estimation information Exploration of the linkages between floodplain hydraulics and in situ observed sedimentationpatterns by: (i) performing a validation of a dynamic 2D river andfloodplain model based on in situ measurements of water depth and flow velocity for a section of a re-meandered 5th order Danishriver channel and floodplain; (ii) compare floodplain flow velocities with measured net deposition of sediment, phosphorus and organicmatter; and (iii) test if simple empirical relationships between floodplain hydraulics and sediment deposition could be developed. Design & implementations Application scale Field Scale Age 10 Performance timescale 5 - 10 years Area (ha) 43,7999992370605 Area subject to Land use change or Management/Practice change (ha) 125 Design capacity description Maximum water detention capacity for the investigated part of the restored river stretch (5%): 3648 m3. If it is assumed thar the remaining 95% of the restored river stretch behave in the same manner, this figure thus represents 5% of the total water volume that can be detained. Basis of design The area affected by flooding during extreme precipitation events was for the investigated river stretch 43,8 ha. If the remaining 95% of restored river stretch behaves in the same manner, the figure only represents 5% of the entire area affected. Constraints The land use in affected areas have to be transformed permanently from e.g. intensively cultivated land to grazed meadows. This will induce a cost to the farmer which requires compensation, either by an annual compensation based on market values for crops or some other metric, or by land aquisition. Re-meandering and creation of wetlands might also be in conflict with infrastructure and residential or commersial housing. Favourable preconditions The evident need to mitigate the effects of the re-occuring flooding events in the downstream towns and villages in the catchment area, together with the availability of land for the purpose of floodplain restauration and wetland creation. Design contractual arrangement Arrangement type Responsibility Role Comments Name Design consultation activity Activity stage Key issues Name Comments Design land use change Land use change type Design authority Authority type Role Responsibility Name Comments Other Implementation Fyn County Faaborg-Midtfyn Municipality is the responsible authority for the project. However it was the former Fyn County who actually carried out the project. After the county decommissioning in 2006 the municipality took over. Lessons, risks, implications... Key lessons Water detention through temporary flooding of wetlands can play a significant role in cutting of flow peaks, and thereby decreasing water levels and floodrisk in downstream towns and villages during incidents of extreme precipitation. Success factor(s) Success factor type Success factor role Comments Specific incentives for stakeholder involvement main factor Financing Financing type Comments National funds Basically it was finaced by a state program under the Danish Nature Agency. However, as time went by, the land prices became higher and higher and in the end the County had to hold the remaining finacing (approx. 50 %). Barrier Barrier type Barrier role Comments Other main barrier The main barriere was the willingness of the landowners to participate in the project, However - the "toolbox" contained several measures (including land consolidation) to overcome this problem. Therefore project succeded in reaching voluntary agreements among the landowners in this project. Driver Driver type Driver role Comments Other main driver The project was part of the national action plan II for the aquatic environment from 1998. The objective was to restore 16.000 ha of wetlands in Denmark to retain nitrogen. The main drivers of the project were the former Danish Counties (they were decommisoned in 2006). Financing share Financing share type Share Comments Policy, general governance and design targets Policy description The measure will prevent flooding in downtream towns and cities. This will have a number of effects on the pressures relevant for the WFD. Reduced risk for flooding of urban environment reduces the risk for storm overflows from sewers ( PN 1.1) aswell as diffuse pollution resulting from flooding in general (PN 2.1). Re-meandering reduces the pressure from previous physical alterations for flood protection and agricultural purposes (PN 4.1.1 and 4.1.2). It will also potentially have a positive effect on ground water recharge in temporarily flooded areas (PN 6.1). Part of wider plan 1 Policy target Target purpose Peak-flow reduction 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 Policy requirement directive Requirement directive Specification Socio-economic Direct benefits information There are no monetary valuation of the direct benefits accruing from the re-meandering and wetlands available. Qualitatively, the direct benefits can be described as reduced risk for flooding in down stream villages, towns and land adjacent to the Odense Å during events of extreme precipitation. Ancillary benefits information The aditional benefits from this measure are connected to the reduction of nutrient leakage and consequent eutrophication in the Odense Å and in the coastal water receiving the river discharge. The riverbed restoration also bring about a strengthened biodiversity as migrating fish and benthos return to the stream. Positive effects can also be anticipated on cultural ecosystem services such as recreation in the affected areas. Costs investment 3120 Costs investment information The figure represents the investment cost per hectare in (in 2014 prices). Costs land acquisition 11400 Costs land acquisition unit €/ha Costs land acquisition information In 2014 prices Costs operation maintenance Not available Costs total 14520 Costs total information The figure represents the investment cost per hectare including cost for land acquisition but exkluding maintenance costs. Ecosystem improved biodiversity 1 Information on Ecosystem improved biodiversity Restoration of riverbeds and re-meandering are themselves measures that strengthen biodiversity in terms of improved biotopes for stream benthos. The periodical flooding of wetlands in connection to the restored river enhances this effect for a number of species, both flora and fauna. Ecosystem provisioning services 0 Ecosystem impact climate regulation Reduced energy use (farm operations) Information on Ecosystem impact climate regulation The conversion from arable land to grazed meadows of land adjacent to the river will result in decreased energy use in farm operations. Biophysical impacts Information on retained water At maximum water detention, approximately 3650 m3 are detained in the investigated area (%5 of the restored river stretch). Assuming that the remaing 95% of the restored river stretch behave in the same manner, the correct figure would be 72 960 m3. Information on increased water storage Since the storage is done in temporary wetlands formed during events of extreme precipitation and consequent flooding of grazing meadows (previously cultivated land) the entire volume can be considered to be an increase compared to the previous situation. Information on runoff reduction Null Water quality overall improvements Positive impact-WQ improvement Information on Water quality overall improvements The removal of nitrogen in the wetlands along the re-meandered river stretch is estimated to 235 kg N/ha/yr Soil quality overall soil improvements N/A info Full Context Pathway(aka Context) Default view Area(aka Level or Site) ALL