flood management systems
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Flood Management Systems
Edward Walsh
DT117/4
C06515036
Sonya Daly
Flood Management Systems Edward Walsh
Table of Contents
WHAT IS FLOODING?..................................................................................................................... 4
FLOOD POLICY IN IRELAND......................................................................................................... 4
FLOOD RISK ASSESSMENT........................................................................................................... 5
FLOOD RISK MANAGEMENT PLANS.......................................................................................... 6
SUSTAINABLE URBAN DRAINAGE SYSTEMS (SUDS)...........................................................7
REFERENCES.................................................................................................................................. 10
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Table of Figures
FIGURE 1: TRENDS IN PRECIPITATION IN IRELAND................................................................................................4
FIGURE 2: SOURCES, PATHWAYS AND RECEPTORS OF FLOODING........................................................................6
FIGURE 3: SWALE AND FILTER STRIP.....................................................................................................................8
FIGURE 4: FILTER DRAIN AND PERMEABLE SURFACE............................................................................................8
FIGURE 5: INFILTRATION BASIN AND SOAKWAY...................................................................................................9
FIGURE 6: DETENTION POND.................................................................................................................................9
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What is Flooding?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.
Figure 1: Trends in Precipitation in Ireland
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.
Flood Policy in Ireland
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.
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
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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.
These guidelines will require the planning system at national, regional and local levels to
follow the following requirements:-
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
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
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The stages of assessment include:
1. Screening Assessment- identifies if there are any flooding or surface water issues
with the development that may require further investigation.
2. 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.
3. 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
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:-
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
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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)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.
The four main methods of control are:-
1. Filter strips and swales
Figure 3: Swale and Filter Strip
2. Filter drains and permeable surfaces.
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Figure 4: Filter drain and Permeable Surface
3. Infiltration devices.
Figure 5: Infiltration Basin and Soakway
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4. Basins and ponds.
Figure 6: Detention Pond
References
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)
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