Post on 11-Sep-2021
Eastern CFRAM Study HA10 Hydraulics Report - DRAFT FINAL
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DOCUMENT CONTROL SHEET
Client OPW
Project Title Eastern CFRAM Study
Document Title IBE0600Rp0028_HA10 Hydraulics Report
Model Name Kilcoole & Newcastle (draft models and reports combined at draft final stage)
Rev Status Author(s) Modeller Reviewed by Approved By Office of Origin Issue Date
D01 Draft Various Various S. Patterson G. Glasgow Limerick/Belfast
Issued as two separate draft reports in June 2014
F01 Draft Final
Various Various S. Patterson G. Glasgow Limerick/Belfast 10/02/2015
F02 Draft Final
Various Various S. Patterson G. Glasgow Limerick/Belfast 13/08/2015
Eastern CFRAM
Study
HA10 Hydraulics Report
Kilcoole & Newcastle Model
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Table of Reference Reports
Report Issue Date Report Reference Relevant Section
Eastern CFRAM Study Flood Risk Review
December 2011
IBE0600Rp0001_Flood Risk Review_F02 3.11.15, 3.11.18
Eastern CFRAM Study Inception Report UoM10
July 2012 IBE0600Rp0005_HA10 Inception Report_F02 4.3.2
Eastern CFRAM Study Hydrology Report UoM10
November 2013
IBE0600Rp0003_HA10_Hydrology Report_D01
4.5
Eastern CFRAM Study HA10 Wicklow Survey Contract Report
May 2013 IBE0600Rp0019_HA10 Wicklow Survey Contract Report_D01
1.2, 1.6, 1.7
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4 HYDRAULIC MODEL DETAILS
4.6 KILCOOLE & NEWCASTLE MODEL
4.6.1 General Hydraulic Model Information
(1) Introduction:
The Eastern CFRAM Flood Risk Review (IBE0600Rp0001_Flood Risk Review) highlighted Kilcoole and
Newcastle as AFAs for fluvial flooding based on a review of historic flooding and the extents of flood risk
determined during the PFRA.
The Kilcoole and Newcastle AFAs were modelled separately at draft hydraulic deliverables stage.
Following the completion of draft models, it was decided to combine the two existing models in order to
accurately represent floodplain interaction between these two AFAs. A combined model, mapping and
reporting has been prepared presenting the draft final results.
All of the watercourses in both AFAs flow to the low lying area to the rear of Leamore Strand behind the
railway embankments before draining to the sea at a point known as The Breaches. As floodwater from
both AFAs is constrained by the railway embankment to the east, this common discharge point at The
Breaches was found to cause considerable fluvial flooding when the outlet under the railway embankment
becomes tidally-locked. As both AFAs drain to the outlet at The Breaches and contribute to flooding, a
combined model was required to accurately represent flooding at this location.
The Kilcoole & Newcastle model represents the overall network of watercourses affecting the Kilcoole and
Newcastle AFAs. The system consists of five distinct catchments draining the inland area between the
coast and the foothills of the Wicklow Mountains to the west, the largest of which is locally known as the
Newtownmountkennedy which drains nearly 15km2. This watercourse is referred to as the Kilmullin for the
purpose of this model. The five main watercourses within the model are Kilcoole, Ballyloughlin, Kilmullin,
Leabeg and Newcastle (moving from north to south).
The catchments are all moderately steep with S1085 values ranging from 12 to 26 m/km. They are
predominantly pasture land with some degree of forest coverage in the mid to upper catchment. There is
some urbanisation in the middle and lower reaches of the catchments as they pass under the N11 and
through the villages of Kilcoole, Newcastle and Newtownmountkennedy.
There is one gauging station within the model extents with continuous flow data available called Druid’s
Glen (10038 – EPA) located on the Newtownmountkennedy watercourse downstream of the N11. The
station has been active since late 2001 and continuous flow data was provided by the EPA up to 2011. An
initial Qmed of 5.3m3/s was based on the AMAX flow data derived using the EPA rating. The EPA rating
suggests there is confidence in the rating up to 1.5m3/s which is approximately half the estimated Qmed and
as such there is little confidence in the observed value of 5.3 m3/s. Rainfall runoff modelling was
undertaken in an attempt to produce a flow record from which a Qmed could be derived. This yielded a Qmed
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value of 3.8m3/s. This value was used to adjust initial Qmed estimations on the Newtownmountkennedy
watercourse but was not considered suitable for use in the other four catchments due to lack of certainty in
the rating. Instead, a pivotal site review indicated that Carrickmines hydrometric station (Stn no. 10022)
was the most appropriate for adjusting initial Qmed estimations. Full details on the hydrological analysis are
included in the UoM10 Hydrology Report IBE0600Rp0003_HA10_Hydrology Report_D01, Chapter 4.5. In
summary, upwards adjustment was undertaken for initial index flow estimations at the HEPs on all five
catchments. This is consistent with the general pattern observed in FSU pivotal sites in that it suggests a
degree of upward adjustment is appropriate for catchments in HA10 and watercourses located along the
eastern coast.
All watercourses within the Kilcoole & Newcastle model have been identified as HPW, and have been
modelled as 1D-2D using the MIKE suite of software. Channel markers have been located at the right and
left banks of all cross sections. Flow within these markers is calculated by the 1D model component,
however when the water level rises sufficiently to meet the bank markers flow can enter the 2D domain
which represents the floodplain.
(2) Model Reference: HA10_KILC8
(3) AFAs included in the model: Kilcoole & Newcastle
(4) Primary Watercourses / Water Bodies (including local names):
Reach ID
1006M
1007A
1007M
1009
1009A
1009C
1011M
1012A
1015F
1015M_V0
Name
COOLDROSS
KILCOOLE TRIBUTARY 1
KILCOOLE
BALLYLOUGHLIN
KILMULLIN (NEWTOWNMOUNTKENNEDY)
BALLYLOUGHLIN TRIBUTARY 1
LEABEG
LEAMORE
KILLADREENAN
NEWCASTLE
(5) Software Type (and version):
(a) 1D Domain:
MIKE 11 (2011)
(b) 2D Domain:
MIKE 21 - Rectangular Mesh
(2011)
(c) Other model elements:
MIKE FLOOD (2011)
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4.6.2 Hydraulic Model Schematisation
(1) Map of Model Extents:
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Figure 4.6.1: Kilcoole & Newcastle Model Overview
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Figure 4.6.2: Kilcoole AFA Extent
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Figure 4.6.3: Newcastle AFA Extent
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Figure 4.6.1 to Figure 4.6.3 illustrate the extent of the modelled catchments, river centre line, HEP
locations and AFA extents as applicable. The Kilcoole & Newcastle catchments contain 8 Upstream Limit
HEPs, 4 Downstream Limit HEPs, 4 Intermediate HEPs, 4 Tributary HEPs and 1 Gauging Station HEP.
(2) x-y Coordinates of River (Upstream extent):
River Name x y
1006M COOLDROSS 331190 208122
1007A KILCOOLE TRIBUTARY 1 326422 208902
1007M KILCOOLE 326968 209453
1009 BALLYLOUGHLIN 328317 207060
1009A KILMULLIN 328490 206442
1009C BALLYLOUGHLIN TRIBUTARY 1 329059 207020
1011M LEABEG 328647 205852
1012A LEAMORE 330728 204125
1015F KILLADREENAN 327360 204638
1015M_V0 NEWCASTLE 327343 204056
(3) Total Modelled Watercourse Length: 30.8km (approx.)
(4) 1D Domain only Watercourse Length: 0km (5) 1D-2D Domain
Watercourse Length:
30.8km
(approx.)
(6) 2D Domain Mesh Type / Resolution / Area: Rectangular / 5m / 46.6km2
(7) 2D Domain Model Extent:
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Figure 4.6.4: 2D Model Grid
Figure 4.6.4 illustrates the modelled extents and the general topography of the catchment. The spatial
extent of the AFA boundary is outlined in black. The reach centre-line is presented in light-blue which also
represents the 1D modelled extent that is within the 2D area. Buildings are excluded from the mesh and
therefore represented as red. Refer to Chapter 3 for details on representation of buildings in the model.
Figure 4.6.5 shows an overview drawing of the model schematisation. Figure 4.6.6 to Figure 4.6.10 show
detailed views. The overview diagram covers the model extents, showing the surveyed cross-section
locations, AFA boundary and river centre line. It also shows the area covered by the 2D model domain.
The detailed areas are provided where there is the most significant risk of flooding. These diagrams
include the surveyed cross-section locations, AFA boundary and river centre. They also show the location
of the critical structures as discussed in Section 4.6.3(1), along with the location and extent of the links
between the 1D and 2D models. For clarity in viewing cross-section locations, the detail diagrams show
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the full extent of the surveyed cross-sections. Note that the 1D model considers only the cross-section
between the 1D-2D links.
Figure 4.6.5: Model Schematisation Overview
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Figure 4.6.6: Detailed Area of Model Schematisation showing Critical Structures
Figure 4.6.7: Detailed Area of Model Schematisation showing Critical Structures
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Figure 4.6.8: Detailed Area of Model Schematisation showing Critical Structures
Figure 4.6.9: Detailed Area of Model Schematisation showing Critical Structures
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Figure 4.6.10: Detailed Area of Model Schematisation showing Critical Structures
(8) Survey Information
(a) Survey Folder Structure:
First Level Folder Second Level Folder Third Level Folder
Murphy_E10_M08_WP3_1011M_121016
Newcastle
Murphy: Surveyor Name
E10: Eastern CFRAM Study Area,
Hydrometric Area 10
M08: Model Number 8
1011M: River Reference
WP3 : Work Package 3
Version: Most up to date
121016– Date Issued (16th OCT 2012)
ss V0_20121016_Ascii
V0_20121016_XS Drawings and
PDFs
V0_20121016_GIS and
Floodplain Photos
Flood_Defence_Register
Flood_Plane_Photos_and_Shap
efiles
Structure_Register
Surveyed_Cross_Section_Lines
Watercourse_Register
V0_20121016_Photos_
Videos
1011m00002I
Photos (Naming
convention is in the
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format of Cross-Section
ID and orientation -
upstream, downstream,
left bank or right bank)
(b) Survey Folder References:
Reach ID Name File Ref.
1006M COOLDROSS Murphy_E10_M08_WP3_1006M_121016
Murphy_E10_M08_WP3_1006A_121108
1007A KILCOOLE
TRIBUTARY 1
Murphy_E10_M08_WP3_1007a_121012
1007M KILCOOLE Murphy_E10_M08_WP3_1007m_121016
Murphy_E10_M08_WP3_1007b_121017
1009 BALLYLOUGHLIN Murphy_E10_M08_WP3_1009b_121012
Murphys_E10_M08_WP3_1009m_121023
1009A KILMULLIN Murphy_E10_M08_WP3_1009a_121016
1009C BALLYLOUGHLIN
TRIBUTARY 1
Murphy_E10_M08_WP3_1009c_121016
1011M LEABEG Murphy_E10_M08_WP3_1011M_121016
1012A LEAMORE Murphy_E10_M08_WP3_1012a_121012
1015F KILLADREENAN Murphy_E10_M08_WP3_1015f_121012
1015M_V0 NEWCASTLE Murphy_E10_M08_WP3_1015m_121017
(9) Survey Issues: The Leabeg watercourse was found to divert from the route outlined in the survey specification at section
1011M00145, chainage 2006. The survey report states that the watercourse turns south and flows through
the right bank away from the specified route, as shown in Figure 4.6.11. The surveyors were unable to find
where the reach flowed to. No channel was found at sections 1011M00135 and 1011M00125 (chainage
2117-2214) and survey drawings indicate that the channel has been filled in. A channel was surveyed
from section 1011M00115 to where this channel enters the Newcastle watercourse, however there is no
link between the upper and lower channels. The lower section of this channel is tidal and has a catchment
area less than 1km2, so it was therefore excluded from the hydraulic model.
The modelled centreline of the Leabeg watercourse was corrected based on aerial photography. The
alignment of this centreline was confirmed by a Senior RPS Technician who walked the route of the
Leabeg to its confluence with the Leamore. Cross-sectional data was added to this section of the
watercourse by interpolating between cross-sections 1011M00145 at the end of the Leabeg and
1012A00048 at the confluence point on the Leamore. This was considered to be a reasonable
methodology as no significant variation in river channel morphology was reported from the site visit. A
short pipe culvert was identified at the entrance to a farm, as shown in Figure 4.6.11, and reasonable
assumptions of diameter, length and invert levels were made based on the characteristics of this channel.
Note that an infill survey of this area has been requested to confirm the validity of these assumptions and
this will be reported on when available.
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Figure 4.6.11: Modelled and specified watercourse layout of Leabeg
The original survey specification for the Kilcoole watercourse (reach 1007M) suggested that the
watercourse splits into two channels at cross-section 1007M00243. This was based on the OPW Blue Line
Network. It was identified in the survey report for this watercourse that the 'original route' (the northern
channel) has been blocked, with the main channel now following the reach designated as 1007b. This
channel consists of dual piped culverts which pass through housing developments on the south side of
Kilcoole. Comments received from Local Authorities at a Draft Mapping workshop held on 22/05/2014 are
consistent with the survey report. The 'original route' to the north was therefore excluded from the model.
The survey data received for Cooldross (reach 1006M) did not extend as far upstream as originally
specified in the survey specification. Survey photos of the upstream end of the reach show that the area is
heavily overgrown making it difficult to locate the channel in this area. As the fluvial inflow from this
channel is relatively small it was considered sufficient to extend the 2D model domain extent to account for
the channel upstream.
The 2D domain was derived using 5m resolution LiDAR data supplied by OPW as described in Section
2.2.2. Localised post-processing of this data was carried out in order to generate an outlet boundary at the
south of the 2D grid. Levels in this area were lowered by approximately 20mm to a level of 1mOD Malin in
order to enable a level boundary to be applied to the edge of the 2D grid. This processing does not affect
design flood estimation in the Kilcoole and Newcastle AFAs.
Watercourse diverts
south at 1011M00145
Leabeg
Leamore Culvert at
farm entrance
Newcastle
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4.6.3 Hydraulic Model Construction
(1) 1D Structures (in-channel along
modelled watercourses):
See Appendix A.1
Number of Bridges and Culverts: 79
Number of Weirs: 20
On the Kilcoole watercourse, flow is restricted by the wall crossing 1007M00301 and the bridge
1007M00292D (Figure 4.6.12), resulting in out-of-bank flooding during design runs of 10% AEP or greater.
This flooding was found to affect agricultural land.
Figure 4.6.12: Wall crossing 1007M00301 and bridge 1007M00292D
Culverts 1007B00090I and 1007B00072I (Figure 4.6.13) on the Kilcoole watercourse become surcharged
during all model design runs, and these culverts were found to cause flooding of properties at Riverside
and Beechdale during design runs of 0.1% AEP. The R761 and Newtown Road were also found to be
affected by this flooding. It should be noted that culverts in this area are reported to be prone to blockage.
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Figure 4.6.13: Culvert 1007B00090I and Culvert 1007B00072I
Culvert 1007M00107I on the Kilcoole watercourse (Figure 4.6.14) was found to restrict flow and cause
flooding from the right bank immediately upstream during design runs of 10% AEP or greater. This
flooding was found to affect agricultural land before rejoining the Kilcoole watercourse downstream.
Overland flow was also found to travel south, away from the Kilcoole watercourse, during design runs of
1% AEP or greater.
Figure 4.6.14: Culvert 1007M00107I
On Ballyloughlin, culverts 1009B00020I and 1009M00321I were found to restrict flow, resulting in flooding
of agricultural land north of the Woodstock Road during design runs of 10% AEP or greater. Flooding was
only found to affect the Woodstock Road during design runs of 0.1% AEP. These culverts are shown in
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Figure 4.6.15.
Figure 4.6.15: Culvert 1009B00020I (left) and culvert 1009M00321I (right)
Culvert 1009M00242I on Ballyloughlin, as shown in Figure 4.6.16, was found to cause flooding on the
R761 during design runs of 1% AEP or greater. The restriction at this culvert is mainly caused by the
culvert profile at its downstream end, which is significantly smaller than that surveyed at the upstream end.
This culvert was therefore modelled based on the surveyed detail at the downstream end of the structure.
Figure 4.6.16: Culvert 1009M00242I
At Kilcoole Golf Course, there a number of restrictive structures which cause flooding during design runs
of 10% AEP or greater. Bridge 1009M00214D causes high afflux during all model design runs, resulting in
flooding from the left bank. Flood water flows into a car park on the left before flowing south through the
golf course. Bridge 1009M00195D also restricts flows, contributing to flooding on both banks during design
runs of 10% AEP or greater. In addition, weir 1009M00189W was found to cause a considerable
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restriction to flow through Kilcoole Golf Course. Flood waters exit the channel on the right bank upstream
of this weir during all model design runs, flowing south and east through the Golf Course. These structures
are shown in Figure 4.6.17.
Figure 4.6.17: Bridge 1009M00214D (top left), bridge 1009M00195D (top right) and weir
1009M00189W (bottom centre)
On Kilmullin, weir 1009A00205W was found to cause flow to back up, resulting in flooding immediately
upstream of bridge 1009A00210D during design runs of 1% AEP or greater. Bridge 1009A00179D was
also found to restrict flow, resulting in flooding from the right bank during design runs of 1% AEP or
greater. These two flooding sources were found to combine and affect the R761 road. These structures
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are shown in Figure 4.6.18.
Figure 4.6.18: Weir 1009A00205W (left) and bridge 1009A00179D (right)
On the Leabeg watercourse, flooding was found to occur during design runs of 0.1% AEP due to
restrictive bridges 1011M00238D and 1011M00225D, as shown in Figure 4.6.19. Flooding was found to
occur from the left bank at bridge 1011M00238D and the right bank at bridge 1011M00225D. Floodwater
flows across the R761 road and rejoins the Leabeg further downstream.
Figure 4.6.19: Bridge 1011M00238D (left) and bridge 1011M00225D (right)
Localised flooding affecting up to five properties and agricultural land was found to occur on the Newcastle
watercourse due to the combination of weir 1015M00500W causing flow to back up and spill over the left
bank, and culvert 1015M00490I restricting flow resulting in flooding from the right bank. These structures
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are shown in Figure 4.6.20.
Figure 4.6.20: Weir 1015M00500W (left) and culvert 1015M00490I (right)
Up to approximately five properties, the Sea Road and agricultural land are at risk of flooding from the
Newcastle reach during design runs of 1% AEP or greater due to bridge 1015M00315D (Figure 4.6.21)
restricting flow.
Figure 4.6.21: Bridge 1015M00315D
All the watercourses within the Kilcoole and Newcastle AFAs drain into a bar-built type estuary with a
common tidal inlet through the railway embankment at 1006A00002D on the Cooldross watercourse, as
shown in Figure 4.6.22. This structure is considered to be clear of debris and operating under normal
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conditions with the model, however it should be noted that the structure is known to become blocked due
to coastal processes depositing shingle at this location.
Figure 4.6.22 Bridge 1006A00002D
(2) 1D Structures in the 2D domain
(beyond the modelled watercourses):
None
(3) 2D Model structures: The hydraulically significant railway embankment located to the
east of the Kilcoole & Newcastle AFAs has been modelled in
the 2D domain. This embankment runs along the coast and
acts as the eastern model boundary from the Irish Sea. Flow
passes through this embankment at one location known locally
as The Breaches. As there is only one outlet location, this
embankment was found to cause fluvial flow from the five
catchments within the Kilcoole & Newcastle AFAs to back up,
resulting in a significant flood risk. As such, it was not deemed
appropriate to classify this embankment as a defence. The
location of this embankment is shown in Figure 4.6.23.
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Figure 4.6.23: Location of hydraulically significant railway embankment
(4) Defences:
None
(5) Model Boundaries - Inflows:
Full details of the flow estimates are provided in the Hydrology Report (IBE0600Rp0003_HA10
Hydrology Report_D01-Section 4.5 and Appendix D). The boundary conditions implemented in the model
are shown below.
Table 4.6.1: Model Boundary Conditions
Outlet at 'The Breaches'
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The layout of the Leabeg watercourse was found to differ from that originally specified in the hydrological
estimation, as discussed in Section 4.6.2(9). The hydrological inputs for this watercourse were reviewed
and it was concluded that it was a reasonable assumption to incorporate the original inputs into the new
watercourse layout as the overall catchment area had not changed substantially.
No adjustments were made to the timing of fluvial inflows. The timing of the downstream coastal boundary
was editing to ensure the peak TWL corresponds roughly with the peak fluvial flows. This is considered to
be a conservative approach for design flood estimation.
Figure 4.6.24 provides an example of the associated upstream hydrographs on the Cooldross,
Ballyloughlin, Kilmullin, Newcastle and Killadreenan at HEPs 10_1371_1, 10_1356_4_RPS,
10_1575_5_RPS, 1494_2_RPS and 10_514_1_RPS respectively during a 1% AEP design run.
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Figure 4.6.24: Inflow hydrographs at HEPS 10_1371_1, 10_1356_4_RPS, 10_1575_5_RPS,
1494_2_RPS and 10_514_1_RPS during 1% AEP design run
(6) Model Boundaries –
Downstream Conditions:
A time-varying water level boundary was applied at the downstream
model extent of the Cooldross (chainage 3950). This is plotted in Figure
4.6.25. This boundary is based on a representative tidal curve and a
normalised surge profile of 40 hour duration, scaled to achieve the ICPSS
50% AEP TWL at Kilcoole. The minimum bed level of the last cross-
section on the Cooldross was surveyed as -0.69mOD Malin, which is
higher than the low water level of the tidal profile. The TWL profile was
therefore edited and all values below -0.69mOD Malin were changed to -
0.68mOD Malin. This ensured that the bed did not dry out at this location
during model design runs and improved model stability. This technique
does not affect peak water level or discharge estimation, and therefore
has a negligible effect on model results.
A level boundary at the South of the 2D model extents was also
established in order to allow flow to leave the 2D domain. This was
required in order to prevent unrealistic water depths from being calculated.
Time
Flo
w (
m3/s
)
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Figure 4.6.25: 50% AEP TWL boundary
(7) Model Roughness:
(a) In-Bank (1D Domain) Minimum 'n' value: 0.030 Maximum 'n' value: 0.070
(b) MPW Out-of-Bank (1D) Minimum 'n' value: N/A Maximum 'n' value: N/A
(c) MPW/HPW Out-of-Bank
(2D)
Minimum 'n' value: 0.013
(Inverse of Manning's 'M')
Maximum 'n' value: 0.070
(Inverse of Manning's 'M')
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Figure 4.6.26: Map of 2D Roughness (Manning's n)
This map illustrates the roughness values applied within the 2D domain of the model. Roughness in the
2D domain was applied based on land type areas defined in the Corine Land Cover Map with
representative roughness values associated with each of the land cover classes in the dataset.
(d) Examples of In-Bank Roughness Coefficients
Killadreenan - 1015F00045 Cooldross - 1006M00232
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Figure 4.6.27: 1015F00045
Manning's n = 0.045
Natural stream - Clean, winding, some weeds and
stones.
Figure 4.6.28: 1006M00232
Manning's n = 0.070
Sluggish Reach - Weedy, deep pools.
Leamore - 1012A00083
Figure 4.6.29: 1012A00083
Manning's n = 0.045
Natural stream - Clean, winding, some weeds and
stones.
Newcastle - 1015M00359
Figure 4.6.30: 1015M00359
Manning's n = 0.050
Natural stream - clean, winding, additional stones.
Kilcoole - 1007B00082J Kilmullin - 1009A00264
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Figure 4.6.31: 1007B00082J
Manning's n = 0.045
Natural stream - Clean, winding, some weeds and
stones.
Figure 4.6.32: 1009A00264
Manning's n = 0.040
Natural stream - Clean, winding, some pools and
shoals.
4.6.4 Sensitivity Analysis
To be completed at Final version.
4.6.5 Hydraulic Model Calibration and Verification
(1) Key Historical Floods (From IBE0600Rp0005_HA10 Inception Report_F02 unless otherwise
specified):
(a) Oct 2011 During October 2011 flooding occurred in Kilcoole following a day of heavy rainfall.
It was reported that road flooding occurred between Greystones and Kilcoole.
Data at Druids Glen hydrometric gauging station (10038) was not available for the
flood event of October 2011, and therefore could not be used to provide an estimate
of the flood event frequency.
Design rainfall frequency was estimated using the FSU Depth Duration Frequency
model (FSU WP 1.2 ‘Estimation of Point Rainfall Frequencies’). No rainfall gauges
in close proximity to the Kilcoole AFA had data available for this event, so rainfall
data at Casement hourly station (approximately 30km North-West of the AFA) was
used. Recordings from this station indicate that 78.9mm of rain fell in an 8 hour
period from 11.00am to 7.00pm on 24th October 2011, equating to a rainfall event of
approximately 1.4% AEP. This should be treated with caution however due to the
considerable distance between the location this rainfall total was recorded at and
the Kilcoole AFA.
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The main road between Greystones and Kilcoole is the R761. Flooding was found
to occur at several locations along this road during model design runs as shown in
Figure 4.6.33. Good verification of model results was therefore achieved.
1. The R761 was found to flood during design runs of 0.1% AEP due to
insufficient capacity of culvert 1007B00090I of the Kilcoole watercourse.
2. Culvert 1009M00242I on Ballyloughlin was found to cause flooding on the
R761 during design runs of 1% AEP or greater.
3. Flooding was found to occur on the R761 during design runs of 1% AEP or
greater due to insufficient capacity of 1009A00179D on the Kilmullin
watercourse.
4. On the Leabeg watercourse, bridge 1011M00225D was found to restrict
flow and cause flooding on the R761 during design runs of 0.1% AEP.
Figure 4.6.33: Model flooding on the R761
(b) Recurring Recurring event. Dates not specified. Heavy rain causes the Newcastle River to
flood the Sea Road and make it impassable.
The model flood extents show flooding on the Sea Road in various locations during
all design runs, as shown in Figure 4.6.34. This is due to out-of-bank flooding from
1
2
3
4
Kilcoole
Ballyloughlin
Kilmullin
Leabeg
R761
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the Newcastle River, which is subject to both fluvial and tidal influences at this
location. Good verification of the model results has therefore been achieved.
Figure 4.6.34: Model flood extents on the Sea Road
Summary of Calibration
The Kilcoole & Newcastle model contains one active hydrometric gauging station, 10038 Druids Glen.
This gauging station has 15 minute flow and water level data available from October 2001 to June 2011,
however no reports of flood events were found for this period so data from this gauging station could not
be used to estimate the frequency of historical flood events.
Data from the hourly rainfall station at Casement (approximately 30km North-West of the AFA) was used
to estimate the frequency of the flood event in October 2011. This should be treated with caution
however due to the considerable distance between Casement rainfall station and the Kilcoole AFA.
Model flows were checked against the estimated flows at HEP check points where possible to ensure
the model is well anchored to the hydrological estimates. For example at HEP 10_1488_5_RPS, the
estimated flow during the 1% AEP design run was 12.36m3/s and the modelled flow was 12.32m
3/s. Full
flow tables can be found in Appendix A.3.
A mass balance check has been carried out on the model to make sure that the total volume of water
entering and leaving the model at the upstream and downstream boundaries balances the quantity of
water remaining in the model domain at the end of a simulation. Refer to Chapter 3.11 for details of
Sea Road
Leamore
Newcastle
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acceptable limits. The mass error in the 1% AEP design run was found to be -3.82%. Further analysis
was undertaken to determine the source of this mass error. Minor instabilities were identified in the tidal
reaches of the Newcastle and Cooldross watercourses. Each of these minor instabilities was reviewed
(as discussed in Section 4.6.6(2)), and as none of the instabilities were found to significantly affect model
results this mass error was considered to be acceptable.
Historical flood data for the Kilcoole and Newcastle AFAs is very limited, and as a result model
calibration could not be undertaken. Good model verification was achieved however from the limited data
available, specifically the Sea Road identified for recurring flooding and the station house which is also
known to flood frequently were found to flood during model design runs of 10% AEP or greater. The
R761 was also found to flood at numerous locations during various model design runs. Despite the
limited calibration and verification data, the model is considered to be performing satisfactorily for design
event simulation.
(2) Public Consultation Comments and Response:
At a Draft flood mapping workshop held on 22/05/2014, Local Authorities confirmed that the original
alignment of the Kilcoole watercourse to the north has been blocked and the watercourse now flows
through the channel to the south. The model is representative.
It was also reported that flooding has occurred in the Beechdale and Meadowbrook areas due to the
Kilcoole watercourse being overgrown and culverts becoming blocked. All bridges and culverts were
assumed to be clear of debris and operating under normal conditions for the model design runs, so these
conditions are not represented. Sensitivity testing for this model is to be undertaken and reported for the
Final version, and it is recommended that this testing incorporates an analysis of culvert blockage in this
area.
Further confirmation was received that the outlet under the railway embankment at the downstream end
of Cooldross is prone to becoming blocked due to shingle. Sensitivity testing for this model is to be
undertaken and reported for the Final version, and it is recommended that this testing incorporates an
analysis of this structure.
In the Newcastle AFA it was reported that the station house has been flooded a number of times. This
property is shown to flood during design runs of 10% AEP or greater, so the model is considered to be
representative.
PCD to be undertaken.
(3) Standard of Protection of Existing Formal Defences:
None
(4) Gauging Stations:
There is one active gauging station associated with this model, 10038 Druids Glen. This is an
unclassified gauge, with 10 years of record from October 2001 to June 2011. This station is an automatic
data logger with water level and flow data available at 15 minute intervals. The rating at the gauging
station is uncertain at flood flows with the highest spot gauging approximately half of the Qmed value.
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Comparison against the FSU estimated value and a value derived from hydrological modelling indicates
that flood flows may be significantly overestimated at this gauging station. This station was not specified
for rating review.
(5) Other Information:
(a) Wicklow Head Office Engineer Meeting No. 2 - Minutes (2005) - This report contains brief
descriptions of several areas of flooding relating to the Kilcoole & Newcastle areas.
'The Breaches (Kilcoole): The culvert at the Breaches is the only outlet for land behind the Railway
Embankment. Shingle washes into outlet causing blockage and flooding of marshlands. Severe flooding
in January 2005.' - A large area of the 'Breaches' was found to flood during fluvial design runs of 10%
AEP (combined with a 50% coastal event). Good verification of model results was therefore achieved.
More significantly, this report has provided an indication of the flooding mechanism associated with this
area, whereby the restriction and blockage of this outlet results in the flooding of a back-barrier area of
marshland. It is deduced that following storm events, storm waves are responsible for the re-deposition
of gravel, ultimately resulting in ridge construction at this location. The restrictive nature of the railway
bridge and associated engineering works at this location therefore prohibits this natural system from re-
establishing an equilibrium following storm events.
As the current model was constructed based on a single set of survey data, it cannot be expected to
reproduce flooding caused by sediment movement and the mechanism for flooding shown by the model
is likely to be different from that described above. Sensitivity testing for this model is to be undertaken
and reported for the Final version, and it is recommended that this testing incorporates an analysis of
this structure.
4.6.6 Hydraulic Model Assumptions, Limitations and Handover Notes
(1) Hydraulic Model Assumptions:
(a) The timing of the downstream coastal boundary was editing to ensure the peak TWL corresponds
roughly with the peak fluvial flows. This is considered to be a conservative approach for design flood
estimation.
(b) The in-channel roughness coefficients were selected based on normal bounds using photographs
delivered as part of the channel and structure survey - it is considered that the final selected values are
representative.
(c) The alignment of the Leabeg watercourse was found to differ from the survey specification. The survey
report states that the watercourse diverts south at cross section 1011M00145, chainage 2006. The
modelled river centreline for the Leabeg was therefore edited based on aerial photography and the
assumed alignment was confirmed during a site visit by a Senior RPS Technician. This is discussed
further in Section 4.6.2(9).
(d) Culvert 1015M00173I was left out of the model as there was inadequate survey information provided.
The location of this structure is shown in Figure 4.6.35. No opening was surveyed at this structure as it is
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heavily overgrown. The bed level of the channel was found to rise by over 1m at this location. The
surveyed section at this location was incorporated into the model and this was considered to provide a
representative restriction to flow due to the notable rise in bed level.
Figure 4.6.35: Location of culvert 1015M00173I
(e) The downstream end of culvert 1007A00020I at chainage 1150 on Kilcoole Tributary 1 could not be
located. The survey report states that manholes along the R774 dual carriageway were checked but none
of them related to this culvert. It is therefore assumed that this culvert joins culvert 1007M00470I on the
Kilcoole watercourse. The assumed layout is shown in Figure 4.6.36.
1015M00173I
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Figure 4.6.36: Assumed layout of culvert 1007A00020I
(2) Hydraulic Model Limitations and Parameters:
(a) The LiDAR data did not extend far enough south to capture the full extent of flooding. An outlet
boundary was therefore added to the model to allow water to leave the model rather than build up and
calculate unrealistic water levels. The 2D grid was not extended to the south using the NDHM as this
flooding is outside the Newcastle AFA extents and there are no receptors to flooding in this area.
(b) A grid resolution of 5 metres has been selected. This resolution was selected as it allows the area of
interest to be modelled in sufficient detail whilst also maintaining good computational performance of the
model.
(c) There is a minor instability at the downstream end of the Newcastle watercourse (chainage 7857).
This instability is mainly due to the tidal influence at this location. It was not possible to eradicate this
instability completely, so its significance and impact on model results was reviewed. This instability causes
fluctuations of up to approximately ±4m3/s in the discharge profile at this location as shown in Figure
4.6.37. This results in fluctuations of up to approximately ±60mm in the calculated water level at this
location. This instability was not found to affect estimations of peak water level, and no erroneous out-of-
bank flooding is caused, so its impact on model results was considered to be low. Peak discharge
estimations at this location should be treated with caution; however as this point is located within the tidally
influenced area of the model the significance of this is low.
Culvert 1007A00020I inlet
Culvert 1007M00470I
Kilcoole
Kilcoole Tributary 1
R774
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Figure 4.6.37: Water level and discharge profiles for 0.1% AEP design run at downstream end of
Newcastle watercourse
(d) There is a minor instability on the Cooldross upstream of its confluence with the Ballyloughlin
(approximate chainage 2531-3352). It was not possible to eradicate this instability completely, so its
significance and impact on model results was reviewed. This instability occurs at the start of the simulation
and causes fluctuations of up to approximately ±5m3/s in the discharge profile at this location as shown in
Figure 4.6.38. This results in fluctuations of up to approximately ±50mm in the calculated water level at
this location. As this instability is only present at the start of the simulation, it was not found to affect
estimations of peak water level or discharge, and no erroneous out-of-bank flooding is caused. Its impact
on model results was therefore considered to be low.
Figure 4.6.38: Water level and discharge profiles for 0.1% AEP design run at chainage 3083 on
Cooldross
(e) There is a minor instability at the downstream end of the Cooldross (chainage 3920), adjacent to
bridge 1006A00002D. This instability is mainly due to the tidal influence at this location. It was not possible
to eradicate this instability completely, so its significance and impact on model results was reviewed. This
Discharge
Water Level
Discharge
Water Level
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instability causes fluctuations of up to approximately ±10m3/s in the discharge profile at this location as
shown in Figure 4.6.39. This results in fluctuations of up to approximately ±50mm in the calculated water
level at this location. This instability was not found to affect estimations of peak water level, and no
erroneous out-of-bank flooding is caused, so its impact on model results was considered to be low. Peak
discharge estimations at this location should be treated with caution; however as this point is located
within the tidally influenced area of the model the significance of this is low.
Figure 4.6.39: Water level and discharge profiles for 0.1% AEP design run at downstream end of
Cooldross at bridge 1006A00002D
Hydraulic Model Parameters:
MIKE 11
Timestep (seconds) 1
Wave Approximation High Order Fully Dynamic
Delta 0.8
MIKE 21
Timestep (seconds) 1
Drying / Flooding depths (metres) 0.02 / 0.03
Eddy Viscosity (and type) 0.50 (Flux Based)
MIKE FLOOD
Link Exponential Smoothing Factor
(where non-default value used)
All links: 0.8
Discharge
Water Level
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Lateral Length Depth Tolerance (m)
(where non-default value used)
All default
(3) Design Event Runs & Hydraulic Model Handover Notes:
(a) The Cross-section and Network files are identical for all design run simulations. The parameters within
the HD parameter file are also identical.
(b) Steady state initial conditions have been used in the 1D model component during all design runs.
(c) Surface elevation initial conditions of -0.68mOD Malin have been used for all locations in the 2D
domain except the outlet boundary at the south of the grid where an initial surface elevation of 1.1mOD
Malin has been specified. As the minimum topographical level in the 2D domain is greater than -0.2mOD
Malin, these initial conditions mean the 2D domain is fully dry at the start of the simulation, except at the
outlet boundary where a low depth of water is present.
(d) The water level exceedance factor was increased to 20 in the Mike11.ini configuration file in order to
achieve model completion. Checks were carried out to ensure previous abnormal completions were not
due to instabilities.
(e) On the Newcastle watercourse, localised flooding of Glen Mill Golf Club was found to occur during
design runs of 10% AEP or greater due to weir 1015M00500W at chainage 1439 causing flow to back up
and spill out-of-bank. This is shown in Figure 4.6.40. Localised flooding from the right bank was also found
to occur during design runs of 10% AEP or greater due to culvert 1015M00490I at chainage 1572
becoming surcharged, as shown in Figure 4.6.40. Up to approximately five properties were found to be
affected by these two flooding mechanisms.
Figure 4.6.40: Model flood extents on the Newcastle watercourse
(f) Flooding was also found to occur from a low left bank on the Newcastle watercourse at section
1015M00465 (chainage 1826) during design runs of 10% AEP or greater, as shown in Figure 4.6.40. This
Glen Mill Golf Club
1015M00500W
1015M00490I
Newcastle Killadreenan
Low left bank at
section 1015M00465
Church Lane
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flooding was found to affect approximately 2 properties, agricultural land and Church Lane.
(g) Bridge 1015M00315D at chainage 3323 on the Newcastle watercourse restricts flow and causes out-
out-bank flooding from both banks during design runs of 1% AEP or greater, as shown in Figure 4.6.41.
Up to approximately five properties, agricultural land and the Sea Road were found to be affected by this
flooding.
Figure 4.6.41: Model flood extents on the Newcastle watercourse
(h) Considerable out-of-bank flooding was found to occur from the left bank of section 1015M00304
(chainage 3431) on the Newcastle watercourse during design runs of 10% AEP or greater, as shown in
Figure 4.6.41. This flooding is due to insufficient channel capacity. Widespread flooding of agricultural land
was found to occur before this flow rejoins the Leamore and Leabeg watercourses. No properties or roads
were found to be affected.
(i) Widespread flooding was found to occur on the lower reaches of the Newcastle watercourse and the
Leamore during design runs of 10% AEP or greater, as shown in Figure 4.6.42. These watercourses are
relatively flat and this area can become tidally locked, leading to severe out-of-bank flooding due to
insufficient channel capacity. This flooding is contained to the east by the railway embankment which runs
along the coastline. The design runs represent the scenario where the watercourse is tidally locked as
they have been undertaken using a 50% AEP coastal water level and the timing of the fluvial and coastal
peak have been roughly aligned. A large area of marshland and agricultural land was found to be affected,
as well as the Sea Road and the landing strip at Newcastle Airfield. The railway was not found to be
Low left bank at
section 1015M00304
Newcastle
Leamore
Leabeg
1015M00315D
Sea Road
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affected by flooding during any design run.
Figure 4.6.42: Model flood extents on the lower Newcastle watercourse
(j) On the Leabeg watercourse, flooding was found to occur due to culverts 1011M00238D and
1011M00225D restricting flow during design runs of 0.1% AEP, as shown in Figure 4.6.43. This flooding
was found to flow overland and affect Leabeg Lane, the R761 and an area of agricultural land before
rejoining the Leabeg downstream. The assumed bridge at the farm entrance lane (as shown in Figure
4.6.43) was also found to contribute to flooding during design runs of 0.1% AEP due to insufficient
capacity. The validity of the assumed dimensions of this structure will be confirmed once outstanding infill
survey data is available.
Newcastle
Outlet to Irish Sea
1006A00002D
Sea Road
Newcastle Airfield
Landing Strip
Leamore
Leabeg
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Figure 4.6.43: Model flood extents on Leabeg
(k) On the Kilcoole watercourse, the wall crossing 1007M00301 and the bridge 1007M00292D both cause
considerable restrictions to flow which results in out-of-bank flooding during design runs of 10% AEP or
greater, as shown in Figure 4.6.44. Agricultural land was found to flood, however no roads or properties
were found to be affected. The headloss effect of both of these structures can be seen in Figure 4.6.51 in
Appendix A.2.
Leabeg
1011M00238D
1011M00225D
Farm Bridge Assumption
R761 Leabeg Lane
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Figure 4.6.44: Model flood extents on the Kilcoole watercourse
(l) On the Kilcoole watercourse, culverts 1007B00090I and 1007B00072I (chainage 3851 and 4035
respectively) cause considerable headloss which results in flooding of properties in Riverside and
Beechdale during design runs of 0.1% AEP. Up to approximately 35 properties were found to be affected,
as well as the Newtown Road and the R761. The modelled flood extents in this area are shown in Figure
4.6.45 and the headloss across culverts in this area can be seen in Figure 4.6.51 in Appendix A.2. It
should be noted that comments received at a Draft flood mapping workshop on 22/05/2014 suggested that
culverts in this area are prone to blockage. Sensitivity testing for this model is to be undertaken and
reported for the Final version, and it is recommended that this testing incorporates an analysis of culvert
blockage in this area.
Kilcoole watercourse
1007M00301
1007M00292D
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Figure 4.6.45: Model flood extents on the Kilcoole watercourse at Riverside and Beechdale
(m) Culvert 1007M00107I at chainage 4752 on the Kilcoole watercourse was found to restrict flow,
resulting in flooding from the right bank immediately upstream during design runs of 10% AEP or greater,
as shown in Figure 4.6.46. This flooding was found to affect agricultural land before rejoining the Kilcoole
watercourse in design runs of 10% AEP. During design runs of 1% AEP or greater overland flow was
found to travel south, eventually joining overland flow from the Ballyloughlin.
Kilcoole Riverside
Beechdale
Newtown Road
R761
1007B00090I
1007B00072I
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Figure 4.6.46: Model flood extents on the lower Kilcoole watercourse
(n) Flooding was found to occur on the Ballyloughlin watercourse during design runs of 10% AEP or
greater due to insufficient capacity of culverts 1009B00020I and 1009M00321I at chainages 319 and 563
respectively. Flooding occurs from the right bank immediately upstream of culvert 1009B00020I, and from
the left bank immediately upstream of culvert 1009M00321I. This flooding was mainly found to affect
agricultural land, however during design runs of 0.1% AEP the Woodstock Road was also found to be
affected, as shown in Figure 4.6.47.
Kilcoole
1007M00107I
Cooldross
Overland flow
from Ballyloughlin
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Figure 4.6.47: Model flood extents on Ballyloughlin
(o) Substantial out-of-bank flooding was found to occur from Ballyloughlin in the vicinity of Druids Glen
and Kilcoole Golf Courses. Culvert 1009M00242I at chainage 1401 was found to have insufficient capacity
and cause flooding during design runs of 1% AEP or greater. As shown in Figure 4.6.48, this flooding
travels overland affecting both golf courses, the R761, up to approximately five properties and agricultural
land before joining overland flow from the Kilcoole watercourse. Further downstream on the Ballyloughlin
watercourse, a number of restrictive structures located within the grounds of Kilcoole Golf Course were
found to cause flooding during design runs of 10% AEP or greater. The main structures which were found
to contribute to flooding are 1009M00214D, 1009M00195D and 1009M00189W at chainages 1660, 1847
and 1890 respectively. The two bridges mentioned were found to have insufficient capacity and weir
1009M00189W was found to cause flow to back up and flood out-of-bank upstream. This results in
widespread flooding of Kilcoole Golf Course during design runs of 10% AEP or greater, and during design
runs of 1% AEP or greater overland flow was found to propagate east and affect agricultural land.
Ballyloughlin
1009B00020I
1009M00321I
Woodstock Rd
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Figure 4.6.48: Model flood extents on Ballyloughlin
(p) Weir 1009A00205W at chainage 1414 on the Kilmullin watercourse causes flow to back up and spill
out-of-bank upstream of bridge 1009A00210D during design runs of 1% AEP or greater. Bridge
1009A00179D at chainage 1688 was also found to restrict flow, resulting in a considerable headloss
across this structure which further exacerbates flooding during design runs of 1% AEP or greater. In
addition, the channel of the Kilmullin watercourse was found to have insufficient capacity in its lower
reaches (downstream of chainage 2173), which results in widespread flooding during design runs of 10%
AEP or greater. Up to approximately 10 properties, the R761 and a large area of agricultural land were
found to be affected by this flooding, as shown in Figure 4.6.49.
Overland flow from
Kilcoole watercourse
Ballyloughlin
1009M00242I
R761
1009M00214D
1009M00195D 1009M00189W Kilmullin
Cooldross
1009A00205W
1009A00210D
1009A00179D
Druids Glen
Golf Course
Kilcoole Golf Course
R761
Kilmullin
Ballyloughlin
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Figure 4.6.49: Model flood extents on Kilmullin
(q) As with the lower Newcastle watercourse, the Cooldross is relatively flat and is prone to becoming
tidally locked when coastal water levels at the Irish Sea are high. This condition has been simulated in the
model design runs as a 50% AEP coastal water level boundary has been applied to the downstream end
of the Cooldross where it discharges under the railway embankment. As floodwater is contained by the
railway embankment to the east, this results in widespread flooding of agricultural land and marshland
during fluvial design runs of 10% AEP or greater, as shown in Figure 4.6.50.
Figure 4.6.50: Model flood extents at Cooldross
(4) Hydraulic Model Deliverables:
Please see Appendix A.4 for a list of all model files provided with this report.
Cooldross
Kilcoole
Ballyloughlin
Kilmullin Newcastle
Outlet to Irish Sea
1006A00002D
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(5) Quality Assurance:
Model Constructed by:
Model Reviewed by:
Model Approved by:
Tanya Ballentine/ David Irwin
Stephen Patterson
Malcolm Brian
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APPENDIX A.1
MODELLED STRUCTURES
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Structure Details – Bridges and Culverts
RIVER BRANCH CHAINAGE ID LENGTH
(m) OPENING
SHAPE HEIGHT (m) WIDTH (m)
SPRING HEIGHT FROM
INVERT (m)
MANNING'S N
BALLYLOUGHLIN 238.1 1009B00027D-bridge 9.8 Irregular 1.13 1.55 N/A 0.013
BALLYLOUGHLIN 319.1 1009B00020I 2.9 Circular 0.90 N/A N/A 0.013
BALLYLOUGHLIN 384.4 1009B00010I 4.0 Circular 0.80 N/A N/A 0.013
BALLYLOUGHLIN 563.5 1009m00321I 4.1 Circular 0.65 N/A N/A 0.013
BALLYLOUGHLIN 733.9 1009m00308I 84.6 Circular 1.00 N/A N/A 0.013
BALLYLOUGHLIN 814.2 1009M00296D-bridge 4.1 Irregular 0.52 4.35 N/A 0.013
BALLYLOUGHLIN 971.7 1009M00280D-bridge 1.2 Irregular x2 1.03, 1.09 3.65, 3.40 N/A 0.013
BALLYLOUGHLIN 1055.4 1009M00272D-bridge 4.6 Irregular 1.24 5.06 N/A 0.013
BALLYLOUGHLIN 1163.5 1009M00261D-bridge 2.9 Irregular 1.35 5.62 N/A 0.013
BALLYLOUGHLIN 1247.9 1009M00252D-bridge 2.5 Irregular 0.74 3.83 N/A 0.013
BALLYLOUGHLIN 1271.8 1009M00250D-bridge 2.6 Irregular 0.68 3.68 N/A 0.013
BALLYLOUGHLIN 1401.5 1009m00242I 91.7 Circular 0.75 N/A N/A 0.013
BALLYLOUGHLIN 1660.3 1009M00214D-bridge 2.5 Irregular 0.44 1.46 N/A 0.013
BALLYLOUGHLIN 1847.3 1009M00195D-bridge 4.7 Arch x2 0.63, 0.76 0.48, 0.41 0.36, 0.57 0.013
BALLYLOUGHLIN 1939.0 1009M00186D-bridge 2.2 Irregular 1.00 7.59 N/A 0.013
BALLYLOUGHLIN 1966.3 1009M00183D-bridge 2.1 Irregular 0.82 4.08 N/A 0.013
BALLYLOUGHLIN 2010.1 1009M00178D-bridge 3.4 Rectangular
x2 0.44 0.63 N/A 0.013
BALLYLOUGHLIN 2113.3 1009M00168D-bridge 3.4 Irregular x2 0.59, 0.57 0.96, 0.86 N/A 0.013
BALLYLOUGHLIN TRIBUTARY 1
83.6 1009C00001D 2.5 Irregular 0.99 5.43 N/A 0.013
COOLDROSS 1657.2 1006M00231D-bridge 6.9 Irregular 0.54 0.97 N/A 0.013
COOLDROSS 1825.1 1006M00214D-bridge 7.4 Arch 1.12 1.47 0.78 0.013
COOLDROSS 2380.9 1006M159D 4.2 Irregular 0.67 2.66 N/A 0.013
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COOLDROSS 3444.1 1006M00052I 12.3 Circular 0.60 N/A N/A 0.013
COOLDROSS 3922.7 1006A00002D-bridge 4.7 Irregular x3 1.30, 2.70,
3.12 13.87, 14.56,
13.38 N/A 0.013
KILCOOLE 935.9 1007M00470I 46.5 Circular 1.80 N/A N/A 0.013
KILCOOLE 1881.6 1007M00373D 7.2 Arch 1.71 2.24 0.45 0.013
KILCOOLE 2592.2 1007M00301 6.0 Irregular 0.29 1.16 N/A 0.013
KILCOOLE 2636.6 1007M00298D-bridge 2.2 Irregular 0.91 2.96 N/A 0.013
KILCOOLE 2686.5 1007M00292D-bridge 1.0 Arch 0.43 0.90 0.00 0.013
KILCOOLE 2857.0 1007M00276I 5.3 Circular x2 0.60 N/A N/A 0.013
KILCOOLE 3435.8 1007B00131I 5.7 Circular x2 1.00 N/A N/A 0.013
KILCOOLE 3717.0 1007B00103I-bridge 15.4 Irregular x2 0.86, 0.83 0.66, 1.07 N/A 0.013
KILCOOLE 3757.1 1007B00100I 38.4 Circular x2 0.90 N/A N/A 0.013
KILCOOLE 3851.2 1007B00090I 20.1 Circular x2 0.90 N/A N/A 0.013
KILCOOLE 3911.6 1007B00084I 17.1 Circular x3 1.00 N/A N/A 0.013
KILCOOLE 4035.5 1007B00072I 16.3 Circular x2 0.90 N/A N/A 0.013
KILCOOLE 4251.7 1007B00049I 2.9 Irregular 1.04 4.38 N/A 0.013
KILCOOLE 4511.0 1007B00024I-culvert 13.1 Irregular 0.84 3.45 N/A 0.013
KILCOOLE 4574.7 1007B00018I-bridge 14.3 Irregular 0.88 3.44 N/A 0.013
KILCOOLE 4752.6 1007M00107I 5.9 Circular x2 0.90 N/A N/A 0.013
KILCOOLE TRIBUTARY 1*
582.1 1007A00077I 130.5 Circular 1.6-1.8 N/A N/A 0.013
KILCOOLE TRIBUTARY 1*
908.5 1007A00045I 159.9 Circular 1.80 N/A N/A 0.013
KILCOOLE TRIBUTARY 1*
1155.5 1007A00020I 164.5 Circular 0.60 N/A N/A 0.011
KILLADREENAN* 732.8 1015F00121I 221.9 Circular x2 1.20 N/A N/A 0.013
KILLADREENAN 854.1 1015F00094I_culvert 11.2 Circular 1.20 N/A N/A 0.013
KILLADREENAN 943.7 1015F00088I_culvert 16.0 Circular 1.20 N/A N/A 0.013
KILMULLIN 456.2 1009A00298D 4.3 Arch 1.66 3.98 0.60 0.013
KILMULLIN 570.2 1009A00287D 3.4 Arch 2.29 5.02 0.99 0.013
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KILMULLIN 625.6 1009A00281D 3.6 Arch 1.73 3.83 0.82 0.013
KILMULLIN 695.9 1009A00274D-bridge 3.1 Arch x5 Between 1.60-1.80
Between 3.00-3.15
Between 0.80-0.95
0.013
KILMULLIN 776.9 1009A00266D-bridge 2.9 Arch x3 3.23, 4.05,
4.50 4.44, 6.10,
6.72 1.21, 2.10,
2.49 0.013
KILMULLIN 907.7 1009A00253D-bridge 4.2 Arch 1.56 4.87 0.43 0.013
KILMULLIN 1002.5 1009A00242D-bridge 4.0 Arch 2.97 6.49 0.93 0.013
KILMULLIN 1236.3 1009A00223D-bridge 5.2 Arch x2 2.49, 3.00 2.62, 3.08 1.60, 1.75 0.013
KILMULLIN 1324.1 1009A00215D-bridge 4.4 Arch 3.85 5.32 2.88 0.013
KILMULLIN 1381.1 1009A00210D-bridge 4.7 Arch 1.86 4.13 0.50 0.013
KILMULLIN 1408.6 1009A00206D-bridge 2.2 Irregular 2.45 8.50 N/A 0.013
KILMULLIN 1430.0 1009A00203D-bridge 7.3 Arch 2.20 4.68 0.74 0.013
KILMULLIN 1688.2 1009A00179D-bridge 7.4 Arch x3 1.15, 1.49,
1.10 1.13, 2.64,
1.41 0.85, 0.80,
0.71 0.013
LEABEG 311.3 25BRDR00318I 83.6 Circular 0.30 N/A N/A 0.013
LEABEG 560.0 1011M00290IA 7.6 Circular 0.50 N/A N/A 0.013
LEABEG 560.0 1011M00290IB 7.6 Circular 0.50 N/A N/A 0.013
LEABEG 650.3 1011M00280I 12.8 Circular 0.50 N/A N/A 0.013
LEABEG 666.8 1011M00278I 3.4 Circular 0.50 N/A N/A 0.013
LEABEG 1073.7 1011M00238D 6.9 Irregular 0.52 0.83 N/A 0.013
LEABEG 1204.8 1011M00225D 8.8 Irregular 0.63 0.68 N/A 0.013
LEABEG 2715.0 Farm Bridge Assumption 2.0 Circular 0.60 N/A N/A 0.013
NEWCASTLE* 577.5 1015M00586I 155.0 Irregular 2.24 5.90 N/A 0.013
NEWCASTLE 1572.6 1015M00490I_culvert 6.9 Circular x6 0.60 N/A N/A 0.013
NEWCASTLE 1983.8 1015M00449D_bridge 1.9 Arch x2 1.34, 1.33 1.70, 1.75 0.90, 0.97 0.013
NEWCASTLE 1989.8 1015M00448D_bridge 4.4 Irregular 1.23 4.29 N/A 0.013
NEWCASTLE 2805.6 1015M00367D_bridge 11.1 Irregular x2 0.91, 1.33 2.43, 5.08 N/A 0.013
NEWCASTLE 3199.9 1015M00328D_bridge 12.2 Irregular 1.10 5.50 N/A 0.013
NEWCASTLE 3323.3 1015M00315D_bridge 5.5 Irregular 0.66 4.53 N/A 0.013
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NEWCASTLE 3608.2 1015M00286D_bridge 3.6 Irregular 0.90 3.91 N/A 0.013
NEWCASTLE 3823.2 1015M00266I_culvert 14.4 Circular 0.60 N/A N/A 0.013
NEWCASTLE 4377.2 1015M00210I_culvert 7.6 Circular 0.35 N/A N/A 0.011
NEWCASTLE 5510.9 1015M00099I 4.7 Circular 0.60 N/A N/A 0.013
NEWCASTLE 5658.0 1015M00095I 13.3 Rectangular 1.01 0.71 N/A 0.013
Structure Details – Weirs
RIVER BRANCH CHAINAGE ID MANNING'S N TYPE
BALLYLOUGHLIN 974.5 1009m00279W 0.013 Broad Crested Weir
BALLYLOUGHLIN 1043.0 1009m00274W 0.030 Broad Crested Weir
BALLYLOUGHLIN 1158.0 1009m00263W 0.045 Broad Crested Weir
BALLYLOUGHLIN 1245.8 1009m00252W 0.013 Broad Crested Weir
BALLYLOUGHLIN 1353.4 1009m00242W 0.013 Broad Crested Weir
BALLYLOUGHLIN 1624.0 1009m00216W 0.040 Broad Crested Weir
BALLYLOUGHLIN 1890.0 1009m00189W 0.013 Broad Crested Weir
BALLYLOUGHLIN 2014.8 1009M00177W 0.050 Broad Crested Weir
BALLYLOUGHLIN TRIBUTARY 1
52.9 10009c00004W 0.045 Broad Crested Weir
KILMULLIN 581.0 1009a00286W 0.013 Broad Crested Weir
KILMULLIN 631.0 1009A280W 0.013 Broad Crested Weir
KILMULLIN 672.3 1009a00276W 0.013 Broad Crested Weir
KILMULLIN 996.4 1009a00244W 0.050 Broad Crested Weir
KILMULLIN 1185.7 1009a00227W 0.013 Broad Crested Weir
KILMULLIN 1197.8 1009a00225W 0.013 Broad Crested Weir
KILMULLIN 1229.2 1009a00223W 0.013 Broad Crested Weir
KILMULLIN 1276.1 1009a00218W 0.013 Broad Crested Weir
KILMULLIN 1316.8 1009a00216W 0.013 Broad Crested Weir
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KILMULLIN 1414.7 1009a00205W 0.045 Broad Crested Weir
NEWCASTLE 1439.0 1015M00500W_weir 0.045 Broad Crested Weir
* Denotes structures incorporated as closed cross-sections only (and are therefore not included in the Network file).
** Structure ID Key:
D - Bridge Upstream Face
E - Bridge Downstream Face
I - Culvert Upstream Face
J - Culvert Downstream Face
W - Weir Crest
NB: All other weirs in the Network file are overtopping weirs which form part of a composite structure with the culvert/bridge at the corresponding chainage.
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APPENDIX A.2
RIVER LONG SECTION PROFILES
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Figure 4.6.51: Kilcoole watercourse 1% AEP design run
Right Bank
Left Bank
Peak Water Level
1007M00301 - Ch. 2595
1007M00292D - Ch. 2685
1007B00090I - Ch. 3851
1007B00072I - Ch. 4035
1007M00107I - Ch. 4752
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Figure 4.6.52: Ballyloughlin 1% AEP design run
Right Bank
Left Bank
Peak Water Level
1009B00020I - Ch. 319
1009M00321I - Ch. 563
1009M00242I - Ch. 1401
1009M00214D - Ch. 1660
1009M00195D - Ch. 1847
1009M00189W - Ch. 1890
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Figure 4.6.53: Kilmullin 1% AEP design run
Right Bank
Left Bank
Peak Water Level
1009A00205W - Ch. 1414
1009A00179D - Ch. 1688
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Figure 4.6.54: Cooldross 1% AEP design run
Right Bank
Left Bank
Peak Water Level
1006A00002D - Ch. 3920
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Figure 4.6.55: Leabeg 1% AEP design run
Right Bank
Left Bank
Peak Water Level
1011M00238D - Ch. 1073
1011M00225D - Ch. 1219
Farm Bridge Assumption - Ch. 2682
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Figure 4.6.56: Leamore 1% AEP design run
Right Bank
Left Bank
Peak Water Level
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Figure 4.6.57: Newcastle watercourse 1% AEP design run
Right Bank
Left Bank
Peak Water Level 1015M00500W - Ch. 1438
1015M00490I - Ch. 1563
1015M00315D - Ch. 3323
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APPENDIX A.3
ESTIMATED PEAK FLOW AND MODEL FLOW COMPARISON
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Peak Water Flows
River Name & Chainage AEP Check Flow (m3/s) Model Flow (m3/s) Diff (%)
KILCOOLE 837.991 10% 0.23 0.23 -2.17
10_30000_1 1% 0.43 0.41 -4.19
0.1% 0.78 0.75 -3.97
KILCOOLE 3109.13 10% 1.42 1.32 -7.11
10_1369_8_RPS 1% 2.66 2.72 2.07
0.1% 4.82 4.38 -9.11
KILCOOLE 4744.46 10% 1.92 1.72 -10.68
10_1369_11_RPS 1% 3.59 3.45 -3.93
0.1% 6.51 5.45 -16.28
KILCOOLE 5485.7 10% 1.92 1.60 -16.56
10_1369_Inter 1% 3.59 2.33 -35.04
0.1% 6.51 3.83 -41.18
KILCOOLE 5642.33 10% 2.60 1.62 -37.81
10_1369_13_RPS 1% 4.87 2.36 -51.46
0.1% 8.82 3.89 -55.86
BALLYLOUGHLIN 3104.61 10% 2.03 1.80 -11.33
10_1573_Inter 1% 3.75 3.00 -20.13
0.1% 6.69 4.75 -29.01
BALLYLOUGHLIN 3356.53 10% 2.27 3.45 52.07
10_1573_7_RPS 1% 4.25 5.27 24.05
0.1% 7.7 9.23 19.88
KILMULLIN 1369.26 10% 6.64 6.95 4.61
10038_RPS 1% 11.81 12.46 5.54
0.1% 20.22 21.49 6.27
KILMULLIN 2891.04 10% 6.85 6.52 -4.85
10_1575_12_RPS 1% 12.43 12.95 4.22
0.1% 21.81 22.35 2.49
LEABEG 3377.71 10% 1.04 0.98 -5.87
10_1581_2_RPS 1% 1.95 1.85 -5.28
0.1% 3.53 3.01 -14.70
LEAMORE 1100.41 10% 8.68 4.94 -43.08
10_1589_1_RPS 1% 15.65 10.34 -33.90
0.1% 27.18 22.85 -15.93
KILLADREENAN 1800.5 10% 1.12 1.17 4.38
10_514_5_RPS 1% 2.1 2.20 4.57
0.1% 3.8 3.74 -1.56
NEWCASTLE 3714.4 10% 6.95 6.79 -2.25
10_1488_5_RPS 1% 12.36 12.32 -0.33
0.1% 21.15 20.46 -3.28
The table above provides details of the flow in the model at every HEP intermediate check point, modelled
tributary and gauging station. These flows have been compared with the hydrology flow estimation and a
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percentage difference provided. It should be noted it was not practical to provide a comparison of modelled
and estimated flows on the Cooldross watercourse due to the extensive flooding in this area.
Good correlation was found between the estimated and modelled flows at HEP 10_30000_1 on the Kilcoole
watercourse, HEPs 10038_RPS and 10_1575_12_RPS on Kilmullin, HEP 10_514_5_RPS at the
downstream end of Killadreenan and HEP 10_1488_5_RPS on the Newcastle watercourse.
On the Kilcoole watercourse, structures 1007M00301 and 1007M00292D were found to restrict flow and
cause out-of-bank flooding, as shown in Figure 4.6.44. The attenuation effect of these structures was found
to cause the modelled flow to drop approximately 7% below the estimated flow at HEP 10_1369_8_RPS
during the 10% AEP design run, however during the 1% AEP design run a higher proportion of flow is able to
overtop bridge 1007M00292D so the modelled flow was found to be approximately 2% higher than the
estimated flow. The modelled flow during the 0.1% AEP design run was found to be approximately 9% lower
than the estimated flow due to the lack of capacity at the wall crossing 1007M00301 and as this structure
could not be overtopped, this leads to a significant headloss.
The differences between modelled and estimated flows at HEP 10_1369_11_RPS on the Kilcoole
watercourse were found to be similar to HEP 10_1369_8_RPS. The modelled flow was found to have
reduced relative to the estimated flow for each design run due to numerous culverts restricting flow including
1007B00090I and 1007B00072I. This was most evident in the 0.1% AEP design run, where the modelled
flow was found to be approximately 16% lower than the estimated flow as out-of-bank flooding was found to
occur due to these culverts during this design run as shown in Figure 4.6.45.
The modelled flow at HEPs 10_1573_Inter and 10_1369_13_RPS on the Kilcoole watercourse was found to
be lower than the estimated flow during all design runs. This is partly due to the restrictive effect of culvert
1007M00107I causing out-of-bank flooding during design runs of 10% AEP or greater, as shown in Figure
4.6.46. The difference between modelled and estimated flows at these HEPs was found to be considerably
greater during design runs of 1% AEP or greater due to overland flow travelling south and bypassing the
HEP checkpoints. This flowpath is shown in Figure 4.6.46.
The modelled flow at HEP 10_1573_Inter on Ballyloughlin was found to be lower than the estimated flow
during all design runs. Considerable flooding was found to occur on this reach in the vicinity of Kilcoole Golf
Course during design runs of 10% AEP or greater, as shown in Figure 4.6.48. This flooding is caused by a
large number of restrictive structures including 1009M002424I, 1009M00214D, 1009M00195D and
1009M00189W, and results in considerable attenuation of the flow in this reach.
The modelled flow at the downstream end of Ballyloughlin (HEP 10_1573_7_RPS) was found to be higher
than the estimated flow during all model design runs. There is considerable flooding at the confluence of
Ballyloughlin and Kilmullin as shown in Figure 4.6.48. The modelled flow at the downstream end of
Ballyloughlin therefore contains a considerable flow contribution from Kilmullin which is not accounted for in
the hydrological estimation, so these differences are considered to be acceptable.
The modelled and estimated flows at the downstream end of Leabeg (HEP 10_1581_2_RPS) shows good
correlation during the 10% AEP and 1% AEP design runs. The modelled flow during the 0.1% AEP design
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run was found to be approximately 14% lower than the estimated flow due to the restrictive effect of culverts
1011M00238D, 1011M00225D and the assumed bridge under the farm lane. These cause flooding as
shown in Figure 4.6.43.
The modelled flow at HEP 10_1589_1_RPS was found to be lower than the estimated flow during all design
runs. This checkpoint is subject to tidal influences, and as such a reliable comparison between modelled and
hydrological estimations of flow is not possible due to tidal flows acting in the opposite direction to fluvial
flows. It is noted however that the modelled flows were found to be approximately 4m3/s lower than the
hydrological estimates for each design run, which provides support for the conclusion that the difference is
only due to the tidal influence within the model.
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APPENDIX A.4
DELIVERABLE MODEL AND GIS FILES
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Fluvial Model Files
MIKE FLOOD MIKE 21 MIKE 21 RESULTS
HA10_KILC8_MF_DES_4_Q10 HA10_KILC8_M21_DES_3_Q10 HA10_KILC8_M21_DES_3_Q10
HA10_KILC8_MF_DES_4_Q100 HA10_KILC8_M21_DES_3_Q100 HA10_KILC8_M21_DES_3_Q100
HA10_KILC8_MF_DES_4_Q1000 HA10_KILC8_M21_DES_3_Q1000 HA10_KILC8_M21_DES_3_Q1000 HA10_KILC8_DFS2_OpenBnd HA10_KILC8_DFS2_FPR HA10_KILC8_DFS2_ISE
MIKE 11 - SIM FILE & RESULTS FILE MIKE 11 - NETWORK FILE MIKE 11 - CROSS-SECTION FILE MIKE 11 - BOUNDARY FILE
HA10_KILC8_M11_DES_9_Q10 HA10_KILC8_NWK_DES_9 HA10_KILC8_XNS_DES_9 HA10_KILC8_BND_DES_2_Q10
HA10_KILC8_M11_DES_9_Q100 HA10_KILC8_BND_DES_2_Q100
HA10_KILC8_M11_DES_9_Q1000 HA10_KILC8_BND_DES_2_Q1000
MIKE 11 - DFS0 FILE MIKE 11 - HD FILE & RESULTS FILE
HA10_KILC8_DFS0_Q10 HA10_KILC8_HD_DES_4_Q10
HA10_KILC8_DFS0_Q100 HA10_KILC8_HD_DES_4_Q100
HA10_KILC8_DFS0_Q1000 HA10_KILC8_HD_DES_4_Q1000
HA10_KILC8_DFS0_Coastal_shifted
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GIS Deliverables - Hazard
Flood Extent Files (Shapefiles) Flood Depth Files (Raster) Water Level and Flows (Shapefiles)
Fluvial Fluvial Fluvial
E22EXFCD100C0 E22DPFCD100C0 E22NFCDC0
E22EXFCD010C0 E22DPFCD010C0
E22EXFCD001C0 E22DPFCD001C0
Flood Zone Files (Shapefiles) Flood Velocity Files (Raster) Flood Defence Files (Shapefiles)
E22ZNA_FCDC0 To be issued with Final version of this report N/A E22ZNB_FCDC0
GIS Deliverables - Risk
Specific Risk - Inhabitants (Raster) General Risk - Economic (Shapefiles) General Risk-Environmental (Shapefiles)
Fluvial E22RIFCD100C0 E22RIFCD010C0 E22RIFCD001C0