European flooding from 1998-2007 caused 700 deaths and displaced 500,000 people with €25 billion in insured losses from 100 major floods from 1998-2002. From 2003-2007 there were 345 deaths and 120 major floods, resulting in €12 billion in insured losses. A catchment flood risk management plan was developed for the 121 square kilometer Dodder catchment area, which identified 1,467 properties at risk of flooding during a 1% annual exceedance probability flood event. The preferred flood risk management option identified was 1,683 meters of flood walls and 351 meters of flood embankments to protect the area from flooding. A strategic environmental assessment was conducted as part of the planning process.

2. European Flooding 1998 - 2002 2003 – 2007
Fatalities 700 345
Major Floods 100 120
Displaced people 500,000 -
Insured economic
Losses
€25 Billion €12 Billion
Figures from Emergency Disasters Database (EM-DAT)
 2002 August (1:100 to 1:500 year event)
 Czech Republic, Slovakia, Italy, Spain, Germany, Romania, Bulgaria, Croatia,
Hungary, and Ukraine
 Vltava, Elbe and Danube rivers reached record highs
 2005 August (>1:200 year event)
 Romania, Germany, Austria, Moldovia, Switzerland, Poland Slovenia,
Serbia
 Danube Rhine

4.  Catchment Flood Risk Management Plan (CFRMP)
 Inception Report
 Hydrology Report
 Hydraulics Report
 Preliminary Options Report
 Urban Drainage Accommodation Report
 Draft Final Report
 Maintenance Report
 Sediment transport model
 Final Report
 Strategic Environmental Assessment (SEA)
 Appropriate Assessment (AA)

5.  121 sq. kilometres (47 sq.
miles)
 Three LA’s DCC, SDCC and
DLRCC
 Main Channel 19km d/s two
reservoirs
 Tallaght Stream 5 km
 Owendoher 10 km
 Whitechurch 8 km
 Little Dargle 8 km
 Dundrum Slang 8 km
 Tidal Region 2 km
 Very steep with a history of
flooding (gradient 1:115)

6.  Hydrometric Data
 Survey data, property
registers
 Environmental areas
 Geotechnical surveys
 Defence Asset Data
 Flooding History
 Previous studies
 Individual Risk Receptors
(IRR), hospitals, fire
stations etc.

7.  Cross-sectional survey
 Bridge & culvert survey
 Weir Survey
 Defence Asset Survey
 Silt surveys
 Large inlet surveys
 Light Detection And Ranging (LiDaR)

8.  Review of historic Floods
 Analysis of Hydrometric & Meteorological data
 Estimation of design floods
 Sensitivity tests for uncertainty
 Climate change
 Catchment changes

9.  Build and verify hydraulic Model
 Model runs for 2,5,10,25,50,100,200 &1000
years flows.
 Sensitivity testing of model
 Freeboard

11.  Development of historical flood maps
 Developing flood extent (risk) maps for 10,
100 (200 tidal) and 1,000 year modelled
events (10%, 1% and 0.1% AEP)
 Development of flood hazard maps
(properties, risk receptors & major
infrastructure under threat)
 Defence failure scenario’s, protected areas
 Risk analysis for Global Warming Scenario

14. Example flood
depth mapping in
the Dodder
Catchment
Example flood hazard
mapping in the
Dodder Catchment

15.  Existing developed land
 Development Plans for
each LA
 Draft Development Plans
 Local Plans
 Area Plans
 Other Plans (drainage,
etc.)

16.  Do nothing
 Tidal Barrage
 Improvement to channel
conveyance
 Relocation of properties *
 Flood Warning system*
 Culverting*
 Diversion of watercourses
 Catchment wide SuDS*
 Proactive Maintenance
 Reactive Maintenance
 Overland Floodways
 Public Awareness Campaign
 Rehabilitation of existing
defences
 Deculverting/ replacing
bridges
 Individual property protection
 Upstream Storage
 Walls and Embankments

17. Core Criteria Objective
Economic
( 30%)
a
Ensure flood risk management expenditure is risk based
Benefit Cost Ratio, 10.0=+30%, 1.0=0%, 0.1=-30%.
Social
( 30%)
a Human Life. Minimise health and safety risk of flood risk management options
b Protect key infrastructure
c Protect existing, and where possible create new waterside access
and recreational and community facilities
d Maintain, and where possible increase, existing waterside access for fishing
Environmental &
Heritage
( 30%)
a Safeguard and promote sustainable land use in keeping with WFD
b
Support the achievement of good ecological status/good ecological potential (GES/GEP)
under the WFD. Particularly morphology as a supporting element to ecological status
c Protect the flora and fauna of the catchment and, where possible, enhance biodiversity,
Remove Alien Species
d Protect, and where possible enhance, fisheries within the catchment
e Protect, and where possible enhance, landscape character and visual amenity
f
Protect and where possible enhance known features of cultural heritage importance and
their settings
Technical
( 10%)
a
Ensure flood risk management options are operationally viable and to minimise
maintenance required.
b Ensure flood risk management options are technically and logistically viable
c Ensure flood risk managed effectively into the future
Other a No increase in flood risk to other areas
• Overall scenario must score positive to become viable option
• Benefit Cost Ratio ≥ 1

18.  Strategic Environmental Assessment of
Dodder CFRAMS.
 SI 436/2004 Planning & Development
(SEA) Regulations 2004, Revoke Art.6 of
2003 Regs.
 Fall out of EU Regs 2001/42/EC.

19. Mammals
Six species of bat were found during the
preparation of the Dodder Habitats
Management Plan. These are;
•Pipistrelle (Pipistrellus pipistrellus)-
most frequently recorded,
•Soprano pipistrelle (Pipistrellus
pygmeaus),
•Leisler’s bat (Nyctalus leisleri),
•Daubenton’s (Myotis daubentonii),
•Brown Long-eared bat (Plecotus
auritus), and
•Whiskered/Brandt’s bats (Myotis
nysticanus/brandti).

20. Cormorant 1 Goosander 1 Sand Martin 3
Wigeon 1 Coot 1, 2 Swallow 3
Teal 1
Black-headed Gull
1
Spotted Flycatcher
1,3
Pochard 1 Common Tern 1 Redpoll 1
Tufted Duck 2 Kingfisher 1, 3
Amber List Species of Medium Conservation
Concern in Ireland recorded in the River
Dodder Conservation Area (adapted from
Newton et al., 1999).

22. Assessment Unit Dodder AU, DS Donnybrook APSR
Water bodies Dodder
Preferred flood risk management option Hard Defences
Flood risk (1% AEP event)
The flood extent maps show that 1467 residential and commercial properties are at risk from flooding from the River Dodder during a 1% AEP
event. The hydraulic model shows that the flood risk is from a combination of out of bank flooding and overland flow.
Receiving Environment
Properties Utility Assets
(No)
Transport
Routes
(length km)
Agricultural Land
(hectares)
Social Amenity (No)
Residential
(No)
Commercial
(No)
1362 105 0 13.13 0 0
Other features and receptors
4 CSOs
11 listed monuments including water mills, bridges, religious sites, houses and enclosures
Land cover – discontinuous urban fabric, industrial and commercial units
Fishery habitat is good for all salmonid life stages throughout most of the Dodder system
No designated protected areas in the vicinity
Important areas of green space which are of significant ecological and natural heritage importance
WFD ecological status is poor
WFD objective is to restore to at least good status by 2021 (extension due to highly impacted sites)
This option consists of hard defences along the left and right bank of the River Dodder. The map shows an indicative line of the location and
extent of the flood defences that would protect the APSR during a 1% AEP event. The preferred option would involve the construction of
1,683m of flood walls and 351m of flood embankments averaging 1.2m above ground level.
Multi Criteria Analysis (MCA) Results
Benefit Cost Ratio (BCR) MCA scores

24.  Sent to EU with plan, SEA & AA statements.
 Every 6 years subsequently
 Major alteration(s) occurs in catchment

25.  OPW
 Suir
 Lee
 Fingal,
East
Meath
 Dodder

36. Thank you
Any Questions?