Flood Management Systems<br />Edward Walsh <br />DT117/4<br />C06515036<br />Sonya Daly<br />Table of Contents<br /> TOC o "
h z u What is Flooding? PAGEREF _Toc257215904 h 4<br />Flood Policy in Ireland PAGEREF _Toc257215905 h 4<br />Flood Risk Assessment PAGEREF _Toc257215906 h 5<br />Flood Risk Management Plans PAGEREF _Toc257215907 h 6<br />Sustainable Urban Drainage Systems (SUDS) PAGEREF _Toc257215908 h 7<br />References PAGEREF _Toc257215909 h 10<br />Table of Figures<br /> TOC h z c "
Figure 1: Trends in Precipitation in Ireland PAGEREF _Toc257215888 h 4<br />Figure 2: Sources, pathways and receptors of flooding PAGEREF _Toc257215889 h 6<br />Figure 3: Swale and Filter Strip PAGEREF _Toc257215890 h 8<br />Figure 4: Filter drain and Permeable Surface PAGEREF _Toc257215891 h 8<br />Figure 5: Infiltration Basin and Soakway PAGEREF _Toc257215892 h 9<br />Figure 6: Detention Pond PAGEREF _Toc257215893 h 9<br />What is Flooding?<br />Flooding is a natural process that can occur at any time in any location and in inevitable part of life in Ireland today. They are mainly caused by overflowing of seas and rivers but prolonged and intense rainfall can cause sewer flooding, overland flooding and groundwater flooding. Flooding has become a more frequent event over the last decade in Ireland causing devastation to people’s properties that are at risk. This increase is primarily due the effect of climate change. Climate change will affect the levels of precipitation in Ireland with an increased hydrological cycle. Changes in weather patterns will occur along with the amounts and characteristics of precipitation. <br />Figure SEQ Figure * ARABIC 1: Trends in Precipitation in Ireland<br />While we cannot prevent flooding from occurring, we can prepare for it and reduce resulting damage and suffering. It is important that a reduction in these future potential flood risks be achieved by incorporating the assessment of flood risk into the planning phase. <br />Flood Policy in Ireland<br />In September 2008, the Department of Environment, Heritage and Local Government and the Department of Finance with responsibility for the OPW published new planning guidelines on The Planning System and Flood Risk Management. This was aimed at ensuring a more consistent, rigorous and systematic approach to fully incorporate flood risk assessment and management into the planning system.<br />These new guidelines are focused on providing for the wide-ranging consideration of flood risk in regional, development and local area plans as well as assessing planning permission applications in line with the proper principles and sustainable development. They also take account of environmental considerations including the need to manage the inevitable impacts of climate change, biodiversity etc., and the EU Directives on Flooding and the Water Framework Directive which established the concept of river basin management.<br />These guidelines will require the planning system at national, regional and local levels to follow the following requirements:-<br />
Building and development is to be evaded in areas with a risk to flooding unless the risk can be managed or reduced to an appropriate level without increasing flood risk elsewhere; and where are sustainable grounds that validate suitable development.
It is of practice to adopt a sequential approach to flood risk management and plan developments away from areas that have been identified as flood prone through flood risk assessment.
Flood risk assessment should be included when making decisions in the planning process.
Flood Risk Assessment <br />
To undertake a flood risk assessment, it is necessary to understand the source of the water, how and where it flows and the hazards that will occur to people and assests affected by it.
Figure 2: Sources, pathways and receptors of flooding<br />The stages of assessment include:<br />
Screening Assessment- identifies if there are any flooding or surface water issues with the development that may require further investigation.
Scoping Assessment- identify the sources of flooding that will affect the site and scope of the extent of the risk, the potential impacts on the development and the possible mitigation measures.
Appropriate Risk Assessment- assessment of flood risk issues in specific detail and provide appraisal of the potential impact on flooding elsewhere and effectiveness of any propped mitigation measures.
Flood Risk Management Plans<br />The aim of Flood Risk Management is to minimise the risks arising from flooding to people, property and the environment. After the assessment phase has been completed, the next stage is to design a flood risk management system. The following actions should be taking into consideration when devising a flood risk management system:- <br />
Flood hazard and potential risk should be identified and considered at the earliest stage in the planning process.
Risks should be reduced or eliminated by developing areas with little or no flood risk.
Development should only be granted in areas of flooding risk where there are no alternative, lower risk sites available in the area.
Future effects of climate change and coastal erosion should only be taken into consideration when designing developments in areas of high risk. A precautionary approach should be employed so that future occupants are no subject to unacceptable risks.
Thorough assessments of flood risks should be undertaken before a review of development plans to ensure compliance with the guidelines, to ensure that land is not zoned or developments granted permission before the risk is fully known.
Land which will be required for future sustainable flood risk management should be identified on local area plans to avoid development in these areas.
Flood risk to, and arising from, new development should be managed through location, layout and design incorporating sustainable drainage systems. E.g. SUDS.
Strategic Environmental Assessment (SEA) of Regional Planning Guidelines, Development and Local Area Plans should include flood risk as one of the key environmental criteria against which such plans are assessed where flood risk has been identified.
The SEA planning guidelines will be updated to reflect the need for flood risk to be identified, assessed and managed.
Sustainable Urban Drainage Systems (SUDS)<br />Sustainable Urban Drainage Systems (SUDS) is an approach to drainage that recognises the wider consequences of urban development. In built-up areas, rainfall has little or no natural drainage route, and so must rely heavily on drainage infrastructure. This concept considers the long term environmental factors in decisions about drainage. They can consist of one or more structures which combined with good management of a site, prevent flooding and pollution. Its main objective is to minimize storm water runoff and to collect and treat this water as close to the source as possible. <br />The four main methods of control are:-<br />
Filter strips and swales
Figure 3: Swale and Filter Strip<br />
Filter drains and permeable surfaces.
Figure 4: Filter drain and Permeable Surface<br />
Figure 5: Infiltration Basin and Soakway<br />
Basins and ponds.
Figure 6: Detention Pond<br />References<br />
Wavin- What is SUDS (n.d.) [Online] Available:
http://ie.wavin.com/master/master.jsp?FOLDER%3C%3Efolder_id=2534374305437765&middleTemplateName=oc_middle_research_sub_sub (Accessed on 23rd March 2010)
Department of Environment, Heritage and Local Government- The Planning System and Flood Management Guidelines (2008)
Department of Environment, Heritage and Local Government (2007) [Online] Available: http://www.environ.ie/en/DevelopmentandHousing/PlanningDevelopment/NationalSpatialStrategy/News/MainBody,18440,en.htm (Accessed on 23rd March 2010)