Dublin City Council has commissioned ByrneLooby (BL) to develop and implement a flood alleviation scheme (FAS) for the River Dodder from Clonskeagh Road Bridge to Orwell Road Bridge including flood defence works on the Little Dargle stream at Braemor Road-Woodside Drive south-eastern junction. This project is known as the River Dodder Flood Alleviation Scheme Phase 3.
Public Consultation Day No. 1
We invited residents, businesses and interested parties to attend the Public Consultation Evening for River Dodder Flood Alleviation Scheme Phase 3.
Representatives from the scheme’s engineering design team, environmental consultants, the Office of Public Works, Dublin City Council and Dun Laoghaire County Council met with and explained the scheme’s objectives and aims to members of the public at the Dropping Wells Pub, Milltown, Dublin on the 14th January 2020.
We would still like to hear about your experience on past floods. Pictures/ Videos of the day/ night of any previous floods you have experienced will be informative to us.
At this early stage we welcome appreciate any ideas and thoughts on possibilities and limitations for flood Relief Scheme so we can take your views into account as we start to develop the scheme options.
Public Consultation Day No. 1 – Response
Dublin City Council, Dun Laoghaire-Rathdown County Council, the Office of Public Works and ByrneLooby would like to thank all attendees who took part in the Public Consultation Day held on the 14th January 2020 at Dropping Wells Pub, Dublin.
All questionnaires from the Public Consultation Day have been received via email, post and hand delivery.
At this early stage we would like to inform members of the public that a formal response with regards to the questions received shall be provided after all submissions have been reviewed and the early stages of the project have progressed to point where informed responses can issue.
Due to the ongoing COVID-19 pandemic, early stage works such as site walkovers and site visits to establish and scope surveys and environmental baselines may be affected.
Dublin City Council, Dun Laoghaire-Rathdown County Council, the Office of Public Works and ByrneLooby would like to advise that these activities will re-commence as soon as possible.
Progress has been steady over the past twelve months during the on-going COVID-19 Pandemic. At this early stage we would like to provide a brief update on the scheme activities from November to December 2020 as follows:
Data collection is complete at this juncture. If any members of the public have any information which could be of use, please contact us.
Dublin City Council have appointed Murphy Surveys to conduct topographical, channel, structural, flood defence and building threshold surveys. During this period, we urge the public to assist the nominated service providers by providing access where possible during their surveys.
Culvert Condition Survey:
Dublin City Council have appointed Ameilo Utilities Ltd to conduct culvert condition survey including CCTV. During this period, we urge the public to assist the nominated service providers where possible during their surveys by provide access.
The hydrological analysis, which includes an assessment of the frequency and magnitude of river flows over a range of scenarios is complete. This, along with the survey data, will provide the necessary inputs to the computer model as part of the hydraulic modelling.
Preparation of a baseline model will commence following receipt of the topographical survey information. It is expected this will occur in January 2021.
Dublin City Council has appointed a number of service providers for ecological surveys along the River Dodder and Little Dargle stream. These surveys include habitats, bat surveys, bird surveys, fish surveys, water quality surveys, invasive species surveys, noise & vibration surveys, land and visual surveys and architectural & cultural heritage surveys in addition other species or features of ecological or environmental interest. All these surveys are ongoing, and it is anticipated that surveys will be complete by February 2021.
A Constraints Report which summarises the main environmental and other project contracts is complete. This will inform the EIAR assessments once the proposed scheme has been defined. EIA screening report has commenced, this will establish whether an EIA is required for the scheme.
Progress has been steady over the past eighteen months during the on-going COVID-19 Pandemic. At this stage we would like to provide a brief update on the scheme activities from December 2020 to May 2021:
The Topographical Survey is complete which includes a level and position survey of the river channel and flood plain as well as all of the structures along the River Dodder including bridges, weirs, walls, etc. A building threshold survey for properties within the flood extent area was also undertaken. Dublin City Council and project team would like to thank the public in assisting the nominated service provider in the completion of the survey.
Culvert Condition Survey:
The Culvert Condition Survey is complete which includes route tracing, geometric measurement and CCTV survey as well as a condition assessment of culverts. Dublin City Council and the project team would like to thank the public in assisting the nominated service provider in carrying out this survey.
Riverbank and Structural Condition Assessment:
The riverbank and structural condition site surveys are completed. Formal and Informal flood defences assessed will be considered as part of the proposed flood alleviation measures for the scheme.
A rating review analysis of Waldron’s Bridge gauge station is currently underway. Results from the analysis will inform necessary inputs to the baseline hydraulic model development.
Overall, the environmental deliverable for the scheme is progressing in line with the required programme. This quarter, two key deliverables have been prepared as follows:
- Environmental Constraints Report for the whole scheme; and
- Environmental Impact Assessment (EIA) Screening Report for the whole scheme.
In addition, further specialist surveys have been continuing to ensure that an up-to-date baseline is established, which forms the basis of the EIA. Specialist surveys completed to date and/or ongoing include:
- Terrestrial ecology surveys (habitats, birds, mammals (e.g. badger, otter, bat), herpetofauna (e.g. reptiles and amphibians), flora, trees, invasive species).
- Aquatic ecology surveys (fish survey, Q values and macroinvertebrate, macrophytes survey, aquatic invertebrate).
- The 2020 invasive alien species survey was updated in March-April 2021.
The next key deliverable for the environmental team is the Environmental Impact Assessment Scoping report, which considers the potential issues relating to the proposed Flood Relief Scheme and discusses which issues are likely to be significant. It will outline how the EIA will deal with each of the issues raised, providing the scope for further desk-based study and site surveys as required. Screening for Appropriate Assessment will also be completed for the scheme as a whole.
Following this the EIA will be carried out with the EIA Report currently scheduled for delivery in Spring 2022.
Progress has been steady over the past twenty-three months during the on-going COVID-19 Pandemic. At this stage we would like to provide a brief update on the scheme activities from May 2021 to September 2021:
The draft hydrology report has been completed for the Scheme area. The report details the analysis completed to define the flows in the rivers during the flooding events. This is a key part in defining how the watercourses in the area respond during flood events. The hydrology focuses on the large Dodder Catchment and the Little Dargle catchments. Understanding how these catchments act a key step is in defining flood risk and developing flood protection measures for the Scheme.
The final hydrology report is currently underway with completion aimed for November 2021.
The hydraulic modelling for the scheme is done using a computer software package to model the watercourses, drainage infrastructure and overland surface. The calculated hydrology is an input to model which is used to represent flood mechanism and evaluate the technical viability of potential flood mitigation measure. Past flood events are used in calibrating the model to ensure it is representative of the flood history in the Scheme area.
Baseline model development is currently underway. The modelling results deduced will identify the properties in the Scheme area at risk of flooding.
A brief update on the scheme activities from October 2021 to December 2021 is provided below:
The draft hydrology report has been updated following completion of the baseline hydraulic model. The baseline model results represented the flows in the rivers during the flood events as well as the extents of the flooding. This provides confidence that the analysis completed of flows in the river mimics historic flood events that occurred. Previous flood event information received from the public and Dublin City and Dun Laoghaire-Rathdown County Councils is being used to verify the baseline model flood extents.
The baseline hydraulic model of the scheme is completed. The calibration and validation of the hydraulic model is underway using data from historical flood events to ensure that it provides an accurate representation of the flooding mechanisms. The baseline model calibration maps will be submitted to the Steering Group for review. Once this is approved the model will be used to produce flood maps and assess and compare various options to alleviate the flood risk.
The Environmental Impact Assessment (EIA) is currently awaiting finalisation of the scheme options before proceeding further. All specialist surveys and studies for aquatic and terrestrial ecology, landscape and visual, archaeology and cultural heritage, noise and vibration and air quality have been completed, with only the aquatic ecology and underwater archaeology reporting to be finalised.
Upon completion of the hydraulic modelling and options assessment, the environmental team will review the baseline ecological survey reports prior to commencing with the EIA Scoping Report. This report aims to provide detail of the potential environmental, social, cultural and heritage impacts of the scheme, and outline a methodology for how these impacts will be assessed in further detail within the Environmental Impact Assessment Report (EIAR).
A brief update on the scheme activities from January 2022 to April 2022 is provided below:
The hydrological analysis has been completed and agreed in principle for the scheme. The Hydrology Report has been finalised following completion of baseline hydraulic model. Flood flows for the watercourses in the area, including the River Dodder, Little Dargle and River Slang have been defined for the design flood event (1% AEP or 1 in 100-year flood event).
Substantial work has been completed on the hydraulic model. The baseline model has now been calibrated and was run for the existing situation. The modelling results identified the properties in the Scheme Area at risk of flooding for various flood events. The model was then revised to include proposed flood defences and run for a range of flood periods to assess the effectiveness of potential flood mitigation measures. These results will feed into the options appraisal for the scheme to the determine the preferred scheme.