River Dee flood risk assessment

Date: 18^th July 2023 To: Dr. Sally Mack­en­zie From: cbec eco engin­eer­ing UK Ltd Pro­ject: River Dee Val­ley Res­tor­a­tion Sub­ject: Flood Risk Assessment

1. INTRO­DUC­TION

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1.1 PUR­POSE OF STUDY The aim of this pro­ject is to under­take a detailed design study for the pro­posed res­tor­a­tion of a 3.6 km reach of the River Dee, between Allan­quoi­ch and Allan­more, west of Brae­mar. This will involve full or par­tial embank­ment remov­al along the river left bank, re-instat­ing chan­nel-flood­plain con­nectiv­ity and thereby improv­ing the qual­ity of in-stream and flood­plain hab­it­ats at the land­scape scale. The study site can be seen in Fig­ure 2.1.

As part of this study, this flood risk assess­ment (FRA) has been com­pleted in sup­port of the pro­posed con­struc­tion, assess­ing any flood risk con­cerns raised by the pro­posed scheme in accord­ance with Scot­tish Plan­ning Policy (SPP).

1.2 SCOPE OF STUDY The assess­ment is a com­pre­hens­ive, risk-based assess­ment of poten­tial flood­ing from all pos­sible sources, includ­ing flu­vi­al flood­ing from adja­cent water­courses, ground­wa­ter and sur­face water run­off. The assess­ment also iden­ti­fies and exam­ines the resid­ual flood risk to the site and any neigh­bour­ing prop­er­ties. The aim of this report is primar­ily to con­sider flood risk and sat­is­fy require­ments under SPP.

Data and inform­a­tion have been obtained from the fol­low­ing sources:

• SEPA; 19/06/2023
• Aber­deen­shire Coun­cil; 19/06/2023
• North East Loc­al Plan Dis­trict — Loc­al Flood Risk Man­age­ment Strategy (LFRMS);
• River Dee Catch­ment Flood Man­age­ment Plan (CFMP)
• topo­graph­ic­al sur­vey data;
• hydraul­ic mod­el­ling results

River Dee Detailed Design Flood Risk Assess­ment 20/07/23 1 cbec eco-engin­eer­ing UK Ltd.

1. BACK­GROUND INFORMATION

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2.1 DEVEL­OP­MENT SITE The devel­op­ment site can be seen in Fig­ure 2 – 1 below:

RIVER DEE VAL­LEY RES­TOR­A­TION — LOC­A­TION MAP

Study Reach River Dee Chan­nel Catch­ment Boundary

RIVER DEE BRAE­MAR CRATHIE

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BIRKHALL N

2150259 PARK AUTHOR­ITY Date 13 JUN 2023 BRAE­MAR CLI­ENT CAIRNGORMS NATION­AL Pro­ject no. PRO­JECT RIVER DEE VAL­LEY 0 5 10 km Drawn Designed RES­TOR­A­TION Reviewed ED GF Scale @ A4‑1:180,000 Brit­ish Nation­al Grid GCS OSGB 1936

Fig­ure 2 – 1 Devel­op­ment site location

The site is rur­al and situ­ated along the River Dee just west of Brae­mar with­in the Cairngorms Nation­al Park. The approx­im­ate grid ref­er­ence for the upstream extent is NO 12259 90688 and the down­stream is NO 14608 92166. The closest vil­lage is Brae­mar which resides to the south east of the down­stream extent of the study area. The Lin of Dee Road runs par­al­lel to the River Dee along the entire study extent.

The study area is situ­ated in a fairly steep val­ley (an elev­a­tion map is shown in Fig­ure 2 – 2) where the bed­rock geo­logy of the study area with­in the chan­nel is pre­dom­in­antly Glen Spean Sub­group Psam­mite. How­ever, there are small areas of Fels­ite, Pel­ite, and Gran­ite sporad­ic­ally situ­ated with­in the flood­plain. This gen­er­ally means the catch­ment is fairly impermeable.

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cbec eco engin­eer­ing RIVER DEE — EXIST­ING CON­DI­TIONS DEM SURFACE

A

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Sur­face DEM elev­a­tions (m) 345 m 320 m

Fig­ure 2 – 2. Elev­a­tion map of study site.

River Dee BRAE­MAR ABER­DEEN­SHIRE UNTAINS 0 200 400 600 800 CLI­ENT CAIRNGORMS NATION­AL Pro­ject no. 2150259 PARK AUTHOR­ITY PRO­JECT RIVER DEE DETAILED DESIGN Date MARCH 2023 Drawn Sur­veyed FD & GP Reviewed KC Scale @ A4‑1:15,000 Brit­ish Nation­al Grid: GCS OSGB 1936 Ser­vice Lay­er Cred­its: Con­tams is data Creen Copy­right and data­base rght 2622 Fath­star fleo­graph­ics, and the tus User Commandy

2.2 DEVEL­OP­MENT PRO­POS­ALS Par­tial or full remov­al of the embank­ment along the north­ern bank of the River Dee has been pro­posed with­in the study extent. Sev­er­al res­tor­a­tion options have been con­sidered, as detailed in the accom­pa­ny­ing ​‘River Res­tor­a­tion Design Report’. A high-level options map for the full embank­ment remov­al option is presen­ted in Fig­ure 2 – 3 for con­text. The final pre­ferred option offers a com­prom­ise between par­tial and full remov­al, with the major­ity of the embank­ment being removed and all hard bank pro­tec­tion on river left removed. Fur­ther details regard­ing the final design are provided in the main pro­ject report.

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cbec eco engin­eer­ing OPTION 3 FULL REMOVAL

Enhance exist­ing high­er qual­ity graz­ing land in con­junc­tion with wet­land man­age­ment Under­take ripari­an plant­ing select­ively along river cor­ridor (loc­a­tions and extents indic­at­ive only and sub­ject to con­sulta­tion) to provide hab­it­at and a future source of large wood Replace exist­ing plastic dams with nature-based options (e.g. leaky wood dams)

Pre­serve and enhance exist­ing good wader hab­it­at along flood­plain margin

Remove entire embank­ment to restore channel/​floodplain con­nectiv­ity and restore nat­ur­al flu­vi­al pro­cess through­out entire res­tor­a­tion extent Add large wood to flood­plain to enhance geo­morph­ic pro­cess and flood­plain diversity and provide dir­ect hab­it­at bene­fits (loc­a­tions indic­at­ive only) Cre­ate wader scrapes to enhance flood­plain hab­it­at (loc­a­tions indic­at­ive only) Install medi­al LWS to enhance nat­ur­al pro­cess and hab­it­at evol­u­tion Install bar apex LWS to enhance nat­ur­al pro­cesses in the chan­nel and encour­age more fre­quent spill onto flood­plain Par­tial or full infilling of ditches using spoil from embank­ment removal/​scrape cre­ation to retain more stand­ing water along north­ern mar­gin of flood­plain and enhance exist­ing good wader habitat

Retain exist­ing embank­ment Remove all bank toe pro­tec­tion along river left bank to remove con­straints to lat­er­al adjust­ment Cre­ate scrapes in areas of exist­ing low topo­graphy Main­tain & enhance graz­ing Retain exist­ing bank pro­tec­tion * In-chan­nel large wood struc­tures Remove embank­ment Remove bank pro­tec­tion Infill/​partially infill ditches Ripari­an plant­ing Flood­plain scrapes Flood­plain large wood Exist­ing wet­land hab­it­at Develop/​enhance woodland/​wet wood­land Replace plastic dams

Fig­ure 2 – 3. Full embank­ment remov­al design proposal.

1. STAT­UTORY CON­SULTA­TION 3.1 SCOT­TISH ENVIR­ON­MENT PRO­TEC­TION AGENCY (SEPA) SEPA was approached regard­ing any known loc­al flood risk or his­tor­ic flood­ing records in the area, of which they noted 10 of the 12 recor­ded flood events along the River Dee were related to flu­vi­al flood­ing. How­ever, these flood events occurred along dif­fer­ing reaches of the River Dee and no inform­a­tion spe­cif­ic to the site is noted.

Full cor­res­pond­ence with SEPA is repor­ted in Appendix A of this Flood Risk Assessment.

3.2 ABER­DEEN­SHIRE COUN­CIL Aber­deen­shire Coun­cil was approached regard­ing any known loc­al flood risk or his­tor­ic flood­ing records in the area.

Full cor­res­pond­ence with the Coun­cil is repor­ted in Appendix A of this Flood Risk Assessment.

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1. PLAN­NING POLICY 4.1 NORTH EAST LOC­AL PLAN DIS­TRICT — LOC­AL FLOOD RISK MAN­AGE­MENT STRATEGY (LFRMS) The North East Loc­al Plan Dis­trict LFRMS was pre­pared and sub­mit­ted in Decem­ber 2022. It does not men­tion any spe­cif­ic issues with the River Dee at Brae­mar, nor any spe­cif­ic object­ives for the catch­ment bey­ond attempt­ing to reduce flood risk where possible.

4.2 DEE CATCH­MENT FLOOD MAN­AGE­MENT PLAN (CFMP) The Dee Catch­ment Flood Man­age­ment Plan was pre­pared and sub­mit­ted in Novem­ber 2007. The pro­posed devel­op­ment site lies in head­wa­ters of the River Dee, situ­ated with­in the Cairngorms. There­fore, there is no spe­cif­ic policy unit alloc­ated to this sec­tion of the River Dee. The Cairngorms Nation­al Park Author­ity (CNPA) ensure the aims lis­ted below are col­lect­ively achieved:

• To con­serve and enhance the nat­ur­al and cul­tur­al her­it­age of the area
• To pro­mote sus­tain­able use of the nat­ur­al resources
• To pro­mote under­stand­ing and enjoy­ment of the spe­cial qual­it­ies of the area by the public
• To pro­mote sus­tain­able eco­nom­ic and social devel­op­ment of the area’s communities

The pro­posed res­tor­a­tion is not designed to spe­cific­ally reduce flood risk, but is in line with restor­ing a more nat­ur­al flow régime and thus sat­is­fies the require­ments of this policy.

4.3 SCOT­TISH PLAN­NING POLICY Scot­tish Plan­ning Policy (SPP) seeks to reduce the impact of flood­ing on new devel­op­ments, by expect­ing developers and plan­ning author­it­ies to err on the side of cau­tion in decision mak­ing whenev­er flood­ing is an issue. In par­tic­u­lar, it requires that no new devel­op­ments should be built on the func­tion­al flood­plain, defined as hav­ing a great­er than 0.5% chance of flood­ing in any giv­en year. Excep­tions may exist where the devel­op­ment loc­a­tion is essen­tial for oper­a­tion­al reas­ons, or can­not be placed elsewhere.

The pro­posed devel­op­ment lies with­in the func­tion­al flood­plain. How­ever, due to the nature of the meas­ures pro­posed the res­tor­a­tion design can­not be placed in an area of lower flood risk, thus this sat­is­fies the require­ments of the SPP.

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1. ASSESS­MENT OF FLOOD RISK 5.1 FLU­VI­AL FLOOD RISK

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5.1.1. SEPA Flood Risk Map The SEPA flood map, shown in Fig­ure 5 – 1, reveals that the devel­op­ment site is loc­ated with­in the func­tion­al flood­plain, at high risk of flood­ing (a 10% chance of occur­ring each year). The primary source of flood­ing to the site is flu­vi­al, deriv­ing from the River Dee.

Braen­ar Auchendryne ee 21:165 Brae­mar River Flood­ing High Like­li­hood Each year this area has a 10% chance of flood­ing. Medi­um Like­li­hood. Each year this area has a 0.5% chance of flood­ing. sesri Crown copy­right and data­base rights (2022) OS 100016991. Con­tains OS Data, use sub­ject to OS Terms and Con…

Fig­ure 5 – 1. SEPA flood zone map — [SEPA Flood Maps (arc​gis​.com)](https://SEPA Flood Maps (arc​gis​.com)).

5.1.2. His­tor­ic flood­ing There are no cur­rent online records avail­able regard­ing his­tor­ic flood­ing along the River Dee. SEPA and Aber­deen­shire Coun­cil have been con­tac­ted and their response is provided in Appendix A.

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5.2 HYDRAUL­IC MOD­EL­LING As part of the design pro­ject, hydraul­ic mod­el­ling of the Dee at the site was under­taken by cbec. The stretch of river at the pro­ject site was mod­elled as exist­ing, and then with the pro­posed design imple­men­ted. The pre- and post-design scen­ari­os have been com­pared, to assess the poten­tial change to flood risk that might occur because of the pro­posed restoration.

A full dis­cus­sion of the hydraul­ic mod­el­ling is included in the main pro­ject report.

The 1 in 10 year res­ults are shown in Fig­ure 5 – 2, the 1 in 200 year in Fig­ure 5 – 3 and the 1 in 200 year plus 37% cli­mate change in Fig­ure 5 – 4.

The res­ults show the extents of the flood­ing remains con­strained with­in the val­ley flood­plain, defined by the steep-sided ter­rain, for all events, with no change between the exist­ing and design scen­ari­os. The max­im­um depth on the flood­plain does increase for the design scen­ario, which is expec­ted giv­en the nature of the res­tor­a­tion scheme.

There is one prop­erty close to the flood­plain, Allan­more (see Fig­ure 5 – 5), poten­tially at risk of flood­ing. The prop­erty itself appears to be on high­er ground, out­with the flooded area, but the access road both to the east and west are affected. The risk does not change though in the pro­posed design case.

There is a barn, owned by Allan­quoi­ch Farm, shown in Fig­ure 5 – 6, with­in the flood­plain. This is the case both for the exist­ing and design scen­ari­os, and the risk does not change in the design scenario.

The pass-for­ward flow hydro­graphs at the down­stream extent of the mod­el were assessed. These demon­strate the flow leav­ing the pro­ject site, and are used to estim­ate the poten­tial effect on down­stream flood­ing the pro­posed design might have. The hydro­graphs are shown in Fig­ure 5 – 7 to Fig­ure 5 – 9. The 200 year and 200 year plus cli­mate change events show neg­li­gible dif­fer­ence in the flow hydro­graphs, sug­gest­ing that the design will have no impact on down­stream flood­ing. Fig­ure 5 – 9 sug­gests this is the case for all events, except the 1 in 2 year, which indic­ates a slight atten­u­ation in the rising limb of the hydro­graph in the design case. The peaks remain the same. This may poten­tially mean a slight atten­u­ation of the 1 in 2 year event down­stream of the site, but the effect is very minor.

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cbec eco engin­eer­ing RIVER DEE — MOD­EL­LING RES­ULTS — WATER DEPTH — 10Y RETURN PERIOD

Exist­ing Conditions

Water Quoi­ch Cairnre Dro­chaide Carr Cottage

Design Con­di­tions

Cairnre Dro­chaide Water Quoich

Water depth (m) Dee Carr Cottage

Dal­gow­an River Dee

Dal­gow­an Mill of Coull Green­feld Linn Of Dee Rd cbec eco engin­eer­ing Inver­chand­lick Cot­tage BRAE­MAR Clunie Water Toll Ho Choin­nich House N

Inver­chand­lick Cot­tage Clunie Water Toll Ho River Dee Mill of Coult ABER­DEEN­SHIRE Strath­don Green­feld Linn Of Dee Ra BRAE­MAR CLI­ENT CAIRNGORMS NATION­AL PARK AUTHOR­ITY PRO­JECT RIVER DEE DETAILED DESIGN Cor­garf acdul CAIRNGORMS Bal­later 0 200 400 600 800 Deeside & Brae­mar Loch­nagar Loch­nagar UNTAINS

Pro­ject no. Date Drawn Mod­elled Reviewed N A 2150259 JULY 2023 ال EG KC Scale @ A4‑1:15,000

Brit­ish Nation­al Grid: Ser­vice Lay­er Cred­its: Con­tains OS data Crown Copy­right and data­base right 2020 Con­tains OS dela Crown Copy­right and data­base night 2022 GCS OSGB 1936 Choin­nich House 1m‑1.5m 1.5m — 2m Exist­ing embank­ment Embank­ment remov­al Pro­posed wet­land Pro­posed LWS Cain Germ prm < 0.25m 0.25m 0.50m 0.50m 0.75m 2m — 3m 0.75m-1m

3m

cbec eco-engin­eer­ing UK Ltd. Fig­ure 5 – 2. Com­par­is­on of 1 in 10 year (10% annu­al chance of occur­ring) flood results.

River Dee Detailed Design Flood Risk Assess­ment 20/07/23 8

cbec eco engin­eer­ing RIVER DEE — MOD­EL­LING RES­ULTS — WATER DEPTH — 200Y RETURN PERIOD

Exist­ing Conditions

Water Quoi­ch Design Conditions

Water Quoi­ch Cairnra Dr Alanaquocth Carr Cot­tag Alana anquoch Cairnra Droshade Dee Carr Cottage

Dal­gow­an River Dee

Dal­gow­an cbec eco engin­eer­ing Invarchand­lick Cot­tage Mill of Cout! Green­fielt Linn Of Dee Ra BRAE­MAR Clunie Water Toll Ho Choin­nich House AGR N

Inver­chandiick Cot­tage Clunie Water Toll Ho River Dee Mill of Coull ABER­DEEN­SHIRE Strath­don Cain Gart CAIRNGORMS Des Green­field Linn Of Dee Rd BRAE­MAR CLI­ENT CAIRNGORMS NATION­AL PARK AUTHOR­ITY PRO­JECT RIVER DEE DETAILED DESIGN Bal­lat­or 0 200 400 600 800 Ser­vice Lay­er Cred­its. Con­tains OS data Crown Copy­right and data­base right 2020 Con­tains OS data Crown Copy­right and data­base right 2022 Choin­nich House Pro­ject no. Date Drawn Mod­elled Reviewed A N A 2150259 JULY 2023 ال EG KC Scale @ A4‑1:15,000 Brit­ish Nation­al Grid: GCS OSGB 1936 Water depth (m) < 0.25m 0.25m 0.50m 1m‑1.5m 1.5m — 2m 0.50m 0.75m 2m — 3m 0.75m — 1m

3m Exist­ing embank­ment Embank­ment remov­al Pro­posed wet­land Pro­posed LWS

cbec eco-engin­eer­ing UK Ltd. Fig­ure 5 – 3. Com­par­is­on of 1 in 200 year (0.5% annu­al chance of occur­ring) flood results.

River Dee Detailed Design Flood Risk Assess­ment 20/07/23 9

cbec eco engin­eer­ing RIVER DEE — MOD­EL­LING RES­ULTS — WATER DEPTH — 200Y RETURN PERI­OD + CLI­MATE CHANGE

Exist­ing Conditions

Cairnra Dy Allanaqu cbec eco engin­eer­ing Invarchand­lick Cot­tage Water Quoi­ch Design Conditions

Water Quoi­ch Water depth (m) < 0.25m Allanaquech arr Cot­tage Cairnra Dre­shak­de 1m — 1.5m Dee 0.25m 0.50m 1.5m — 2m 0.50m 0.75m 2m — 3m 0.75m — 1m

3m Carr Cottage

Dee Dal­gow­an River Dee Mill of Coull Green­field Clunie Water Toll Hot Choin­nich House N Linn Of Dee Ra Inver­chand­lick Cot­tage Clunie Water Toll Hot Choin­nich House A99 N

Dal­gow­an River Dee Mill of Coull ABER­DEEN­SHIRE Strath­don Cabn Cor­garf Green­field Linn Of Dee Ra BRAE­MAR CLI­ENT CAIRNGORMS NATION­AL PARK AUTHOR­ITY PRO­JECT RIVER DEE DETAILED DESIGN 400 600 800 CAIRNGORMS Bal­later 0 200 Deeside & Dee Brae­mar Loch­nagar A Lech­magar NTAINS Pro­ject no. Date Drawn Mod­elled Reviewed 2150259 JULY 2023 ال EG KC Scale @ A4‑1:15,000

Brit­ish Nation­al Grid: GCS OSGB 1936 Exist­ing embank­ment Embank­ment remov­al Pro­posed wet­land Pro­posed LWS

Fig­ure 5 – 4. Com­par­is­on of 1 in 200 year (0.5% annu­al chance of occur­ring) plus 37% cli­mate change flood results.

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Fig­ure 5 – 5. Allan­more prop­erty, close to the floodplain.

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River Quoi­ch Fig­ure 5 – 6. Allan­quoi­ch Farm barn, situ­ated with­in the floodplain.

Pass for­ward dis­charge [m³/​s] 600.00 500.00 400.00 300.00 200.00 100.00 0.00 4 9 14 19 24 29 Time [h] EC 200Y DE 200Y

Fig­ure 5 – 7. Pass-for­ward flow hydro­graphs for exist­ing and design cases, for the 1 in 200 year event.

River Dee Detailed Design Flood Risk Assess­ment 20/07/23 12 cbec eco-engin­eer­ing UK Ltd. cbec eco engineering

Pass for­ward dis­charge [m³/​s] 800.00 700.00 600.00 500.00 400.00 300.00 200.00 100.00 0.00 4 9 14 19 24 29 Time [h] 600.00 EC 200Y+37% DE 200Y+37%

Fig­ure 5 – 8. Pass-for­ward flow hydro­graphs for exist­ing and design cases, for the 1 in 200 year plus 37% cli­mate change event.

Pass for­ward dis­charge [m³/​s] EC 2Y 500.00 DE 2Y EC 5Y 400.00 DE 5Y EC 10Y 300.00 DE 10Y EC 30Y 200.00 DE 30Y 100.00 EC 50Y DE 50Y 0.00 EC 100Y 3 8 13 18 23 28 DE 100Y Time [h]

Fig­ure 5 – 9. Com­par­is­on of pass-for­ward flow hydro­graphs for all events.

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5.3 SUR­FACE WATER FLOOD RISK

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5.3.1. Sur­face water flood risk to the scheme While the primary source of flood­ing to the pro­posed scheme is flu­vi­al, Fig­ure 5 – 10 high­lights the risk of sur­face water flood­ing to the site.

River Dee River Dee Brae­mar Auchendryne Brae­mar River Dee Sur­face Water Flood­ing High Like­li­hood Each year this area has a 10% chance of flood­ing. Medi­um Like­li­hood Each year this area has a 0.5% chance of flood­ing. Low Like­li­hood River Dee 124 – 165 Each year this area has a 0.1% chance of flood­ing. Crown copy­right and data­base rights (2022) OS 100016991. Con­tains OS Data, use sub­ject to OS Terms and Con… esi

Fig­ure 5 – 10 SEPA Sur­face water flood risk map — [SEPA Flood Maps (arc​gis​.com)](https://SEPA Flood Maps (arc​gis​.com))

The areas where sur­face water flood­ing poses a risk are clas­si­fied in four cat­egor­ies as follows:

• High — A flood event is likely to occur in the defined area on aver­age once in every ten years (1:10). Or a 10% chance of hap­pen­ing in any one year.
• Medi­um — A flood event is likely to occur in the defined on aver­age once in every two hun­dred years (1:200). Or a 0.5% chance of hap­pen­ing in any one year.
• Low — A flood event is likely to occur in the defined area on aver­age once in every thou­sand years (1:1000). Or a 0.1% chance of hap­pen­ing in any one year.

5.3.2. Sur­face water flood risk from the scheme As the site is cur­rently Green­field and will remain Green­field after the con­struc­tion of the pro­posed devel­op­ment, and all pro­posed works are con­tained with­in the exist­ing chan­nel, it is unlikely that the pro­posed works will have any impact on the sur­face water flood risk.

5.4 GROUND­WA­TER 5.4.1. Ground­wa­ter flood risk to the scheme North East Loc­al Plan Dis­trict LFRMS shows the devel­op­ment area to be in an area of low ground­wa­ter flood risk. How­ever, there are no know ground­wa­ter flood­ing issues in the area, neither his­tor­ic nor pre­dicted to change due to cli­mate change. Due to the nature of the devel­op­ment, risk of ground­wa­ter flood­ing is negligible.

5.4.2. Ground­wa­ter flood risk from the scheme As the pro­posed devel­op­ment will not add any hard­stand­ing areas or impact any poten­tial ground­wa­ter sources or flow paths there­fore, there will be no increase in ground­wa­ter flood risk caused by the development.

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5.5 STRUC­TURES There is one struc­ture upstream of the site, included in the mod­el. This is a small bridge over the Quoi­ch Water. Mod­el res­ults show that the deck is approx­im­ately 600 mm above the peak 1 in 200 year plus 37% cli­mate change water level though. This does not change in the design scen­ario, so the struc­ture is not con­sidered a risk factor.

Fig­ure 5 – 11. Bridge at Quoi­ch Water.

5.6 SEW­ER­AGE INFRA­STRUC­TURE Quoi­ch Wate No prop­er­ties are with­in the scheme site, thus there is deemed to be no impact on any sew­er­age infrastructure.

5.7 MIT­IG­A­TION OPTIONS The hydraul­ic mod­el­ling indic­ates a gen­er­al increase in flood depths in the flood­plain, but no oth­er impacts on flood extents or down­stream flows have been found. The increase in flood­plain depths is com­men­sur­ate with the res­tor­a­tion meas­ures, but there are no flood recept­ors affected by this. As such, no flood mit­ig­a­tion meas­ures are necessary.

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