General National Id Ireland_001 Site name River Tolka Summary The River Tolka runs through Dublin, Ireland. A series of measures was applied to the urban sections of the river to slow flood flows, reduce pollution and support wildlife. These included the establishment of retention ponds to manage runoff storage; bank engineering to slow flows and prevent erosion; and planting trees along the river to slow runoff. Two phases of retention pond construction have been carried out, the latter as part of a wider ‘Greenway’ project to develop a green corridor with cycling route. Light or indepth? In-depth The in-depth description of the case study cs-ire-01-final_version.pdf Location description The River Tolka is located in eastern Ireland. It flows eastwards through Dublin and in to the Irish sea. The improvement sites are located along the urban reaches of the Tolka, particularly at the Tolka Valley Park. NUTS Code Southern and Eastern RBD code IEEA Transboundary 0 Data provider Heather Williams, AMEC Source(s) The Tolka catchment - fulfilling multiple roles: local government perspectives Tolka Valley Greenway opening speech by Lord Mayor Performance Assessment of an Integrated Constructed Wetland-Pond System in Dublin, Ireland The Tolka catchment - fulfilling multiple roles: local government perspectives Biodiversity Survey of the Integrated Constructed Wetland at Tolka Valley Park, Finglas, Co. Dublin Impact Assessment Of Urbanisation On Hydrology For The River Tolka In Dublin, Ireland: A Case Study Of Remote Sensing Supported Hydrological Modelling NWRM(s) implemented in the case study Wetland restoration and management Urban forest parks Natural bank stabilisation Basins and ponds Longitude -6.303277 Latitude 53.377121 Site information Climate zone cool temperate moist Mean rainfall 715 Mean rainfall unit mm/year Average temperature 11 Mean runoff 357 Mean runoff unit 450 - 600 mm Average runoff coefficient 0,5 Type Case Study Info Monitoring maintenance Monitoring impacts effects 1 Monitoring parameters There has been varied monitoring at the Tolka. Monitoring relevant to the NWRMs include ecology surveys (incl. macrophytes, amphibians, invertebrates), and water quality monitoring. Performance Performance impact estimation method Catchment outlet Performance impact estimation information Performance of the retention ponds/ wetlands is monitored by measurements of water quality and observation of fauna and flora Design & implementations Application scale River Installation date 2000 Performance timescale < 1 year Area (ha) 18.2 ha Area specifications The total size of the Tolka Valley Park is 18.2 ha. Constraints Constructed wetlands depend on suitable hydrological regime that allows permanent presence of water in them. Favourable preconditions Availability of parkland space prior to the project 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 Initiation of the measure Dublin City Council City Council Other Financing National Transport Authority Funded Greenway NGO Other Tolka Trout Anglers Volunteer work Other Atkins Global Consultants Lessons, risks, implications... Key lessons - Parks in urban areas can serve as biodiversity reserves and offer opportunities to contribute to achieving good ecological status of waterbodies under the WFD. - Soft engineering techniques can be cost-effective and enhance the biodiversity potential of urban cactchments. - Local community involvement is key to project success. Success factor(s) Success factor type Success factor role Comments Attitude of relevant stakeholders main factor Attitude of the public secondary factor Financing Financing type Comments Barrier Barrier type Barrier role Comments Driver Driver type Driver role Comments Balancing different objectives main driver There were multiple objectives to the improvements to the Tolka, relating to the WFD, Floods Directive, EU LIFE Project, "Greenway" development, recreational and access objectives in Dublin Financing share Financing share type Share Comments Policy, general governance and design targets Policy description The Tolka has poor ecological status (WFD) due to diffuse pollution (urban runoff) and point pollution (waste disposal sites) Part of wider plan 1 Policy target Target purpose Pollutants Removal Peak-flow reduction Improved Biodiversity Oher Societal Benefits 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 National Environment & Biodiversity Renew4GPP (Ireland pilot project) Control of invasive species Policy requirement directive Requirement directive Specification Socio-economic Costs total 4100000 Costs total information Full cost of the 'Greenway' programme of which the ponds and wetlands were part Compensations annual information Assume none (land was already public parkland prior to implementation) Information on Economic costs - income loss Assume none (land was already public parkland prior to implementation) Ecosystem improved biodiversity 1 Information on Ecosystem improved biodiversity The ecology of the river has improved as a result of these measures and other improvements in the catchment. Otter and salmon have now returned to the Tolka catchment (altough NWRMs are only some of the actions that have contributed to this). Ecosystem provisioning services 1 Information on Ecosystem provisioning services Angling quality has improved as a result of these and other actions in the Tolka catchment. Ecosystem impact climate regulation No specific impact Biophysical impacts Ecosystem erosion control 1 Water quality overall improvements Positive impact-WQ improvement Information on Water quality overall improvements The wetland influences water quality on its own. In addition, barley straw bales were added to ponds in 2012 to prevent algal blooms (and can be assumed to have been successful, since there has been no evidence of the algae since). Information on Ecosystem erosion control impact Before and after photos of sediment capture measures reveal less exposed soil on river banks. Wq Improvements n unit % reduction pf pollutant Information on Water quality Improvements (N) The constructed integrated wetland achieved: - 91% reduction in ammonia concentrations - 16% reduction in nitrate concentrations - 6.5% reduction in nitrite concentrations. The addition of barley straw provided further benefits, reducing ammonia by 55% and nitrate by 38% Information on Water quality Improvements (e.coli) The addition of barley straw to the pond/weltand achieved a 99% reduction in e-coli concentrations Soil quality overall soil improvements N/A info Information on Soil quality overall soil improvements Some erosion control measures were implemented on the floodplain of the River Tolka. These measures may improve soil quality by retaining soils, but no specific information was available. Full Context Pathway(aka Context) Default view Area(aka Level or Site) ALL