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Eastern CFRAM Study HA10 Hydraulics Report - DRAFT FINAL

IBE0600Rp0028 F02

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


IBE0600Rp0028 F02

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


IBE0600Rp0028 4.6-1 F02

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


IBE0600Rp0028 4.6-2 F02

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


IBE0600Rp0028 4.6-5 F02

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:


IBE0600Rp0028 4.6-8 F02

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


IBE0600Rp0028 4.6-9 F02

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



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(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.


IBE0600Rp0028 4.6-14 F02

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


IBE0600Rp0028 4.6-15 F02

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.


IBE0600Rp0028 4.6-16 F02

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


IBE0600Rp0028 4.6-17 F02

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


IBE0600Rp0028 4.6-18 F02

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


IBE0600Rp0028 4.6-19 F02


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


IBE0600Rp0028 4.6-20 F02


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


IBE0600Rp0028 4.6-21 F02

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.


IBE0600Rp0028 4.6-22 F02

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'


IBE0600Rp0028 4.6-23 F02

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.


IBE0600Rp0028 4.6-24 F02

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

)


IBE0600Rp0028 4.6-25 F02

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')


IBE0600Rp0028 4.6-26 F02

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


IBE0600Rp0028 4.6-27 F02

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


stones.

Newcastle - 1015M00359

Figure 4.6.30: 1015M00359

Manning's n = 0.050

Natural stream - clean, winding, additional stones.

Kilcoole - 1007B00082J Kilmullin - 1009A00264


IBE0600Rp0028 4.6-28 F02

Figure 4.6.31: 1007B00082J

Manning's n = 0.045


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.


IBE0600Rp0028 4.6-29 F02

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


IBE0600Rp0028 4.6-30 F02

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


IBE0600Rp0028 4.6-31 F02

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.


IBE0600Rp0028 4.6-32 F02

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


IBE0600Rp0028 4.6-33 F02

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


IBE0600Rp0028 4.6-34 F02

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


IBE0600Rp0028 4.6-35 F02

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


IBE0600Rp0028 4.6-36 F02

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


IBE0600Rp0028 4.6-37 F02

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


IBE0600Rp0028 4.6-38 F02

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


IBE0600Rp0028 4.6-39 F02

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


IBE0600Rp0028 4.6-40 F02

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


IBE0600Rp0028 4.6-41 F02

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


IBE0600Rp0028 4.6-42 F02

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


IBE0600Rp0028 4.6-43 F02

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


IBE0600Rp0028 4.6-44 F02

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


IBE0600Rp0028 4.6-45 F02

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


IBE0600Rp0028 4.6-46 F02

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


IBE0600Rp0028 4.6-47 F02

(5) Quality Assurance:

Model Constructed by:

Model Reviewed by:

Model Approved by:

Tanya Ballentine/ David Irwin

Stephen Patterson

Malcolm Brian


IBE0600Rp0028 4.6-48 F02

APPENDIX A.1

MODELLED STRUCTURES


IBE0600Rp0028 4.6-49 F02

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 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 1847.3 1009M00195D-bridge 4.7 Arch x2 0.63, 0.76 0.48, 0.41 0.36, 0.57 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


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


IBE0600Rp0028 4.6-50 F02

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 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


908.5 1007A00045I 159.9 Circular 1.80 N/A N/A 0.013


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



IBE0600Rp0028 4.6-51 F02


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 1236.3 1009A00223D-bridge 5.2 Arch x2 2.49, 3.00 2.62, 3.08 1.60, 1.75 0.013



KILMULLIN 1408.6 1009A00206D-bridge 2.2 Irregular 2.45 8.50 N/A 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




IBE0600Rp0028 4.6-52 F02


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 2014.8 1009M00177W 0.050 Broad Crested Weir


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









IBE0600Rp0028 4.6-53 F02


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.


IBE0600Rp0028 4.6-54 F02

APPENDIX A.2

RIVER LONG SECTION PROFILES


IBE0600Rp0028 4.6-55 F02

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


IBE0600Rp0028 4.6-56 F02

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


IBE0600Rp0028 4.6-57 F02

Figure 4.6.53: Kilmullin 1% AEP design run

Right Bank

Left Bank

Peak Water Level

1009A00205W - Ch. 1414

1009A00179D - Ch. 1688


IBE0600Rp0028 4.6-58 F02

Figure 4.6.54: Cooldross 1% AEP design run

Right Bank

Left Bank

Peak Water Level

1006A00002D - Ch. 3920


IBE0600Rp0028 4.6-59 F02

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


IBE0600Rp0028 4.6-60 F02

Figure 4.6.56: Leamore 1% AEP design run

Right Bank

Left Bank

Peak Water Level


IBE0600Rp0028 4.6-61 F02

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


IBE0600Rp0028 4.6-62 F02

APPENDIX A.3

ESTIMATED PEAK FLOW AND MODEL FLOW COMPARISON


IBE0600Rp0028 4.6-63 F02

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


IBE0600Rp0028 4.6-64 F02

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


IBE0600Rp0028 4.6-65 F02

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.


IBE0600Rp0028 4.6-66 F02

APPENDIX A.4

DELIVERABLE MODEL AND GIS FILES


IBE0600Rp0028 4.6-67 F02

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_Coastal_shifted


IBE0600Rp0028 4.6-68 F02

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

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