[PPT] - Stranraer Flood Protection Scheme: A case Study Juan Fernandez, PowerPoint Presentation

SLIDE 1

Stranraer Flood Protection Scheme: A case Study

Juan Fernandez, Simon McGee, Alasdair Fraser

Mouchel The Beta Centre Stirling University Innovation Park Stirling, FK9 4NF Scotland, UK 4th International Symposium on Flood Defence: Managing Flood Risk, Reliability and Vulnerability Toronto, Ontario, Canada, May 6-8, 2008

SLIDE 2

1

I ntroduction

Stranraer is located in South West Scotland, in

the Dumfries and Galloway Council

Population of around 13,000
Ferry port connection
Historical flooding issues
October 2000 event
Scottish Water and Council competences
Drainage Area Plan

Stranraer

October 2000 flooding around the Sheuchan Burn Stranraer Location

SLIDE 3

2

Stranraer Watercourses

Black Stank
Town Burn
Laundry Burn
Sheuchan Burn
Surface water

sewers

Stranraer watercourses

SLIDE 4

3

Data Gathering

Site visits
Topographic survey
Watercourse survey
Floodplain survey
Structural survey
3D survey
CCTV survey
DAP survey
Manhole survey
Pumping Station survey
CCTV survey
CSO survey

Stills from Millburn Court CCTV Survey (John Bunting, EEC - 7 July 2005) Stranraer topography

SLIDE 5

4

Data Gathering

Hydrology
Rainfall data from 4 raingauges (MET office, 2000)
Flood Estimation Handbook (FEH) methodology
Climate Change (Price and McKenna, 2003)
Extreme sea-water levels for Stranraer (HR Wallingford, 2002)
Joint probability assessment (DEFRA, 2006)

Current Estimated Peak Flows (m3/s) Return Period (year) 2.33 5 10 25 50 100 200 500 Black Stank 3.16 4.38 5.24 6.66 7.83 8.98 10.35 12.48 Town Burn 1.26 1.62 1.88 2.22 2.4 2.53 2.65 2.81 Reach B 1.09 1.58 1.89 2.34 2.81 3.27 3.82 4.68 Reach A 1.06 1.57 1.89 2.36 2.75 3.21 3.77 4.63 Sheuchan Burn Whole 2.5 3.66 4.39 5.46 6.42 7.51 8.78 10.76 Laundry Burn 1.22 1.82 2.21 2.77 3.26 3.73 4.37 5.35

Estimated Peak Flows (m3/s) for Stranraer Watercourses

Return Period (years) Extreme water level (m AOD) 1 2.65 10 3.00 25 3.14 50 3.23 100 3.38 250 3.52

Extreme Water Levels for Stranraer

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5

Hydraulic Modelling

Combination of different hydraulic software packages
HEC-RAS (1D – open watercourses)
InfoWorks CS (1D – long culverts and drainage system)
MIKE21 (2D – overland flow)
Watercourses and sewage system interactions
Water depths were predicted at every single flooded property

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6

Hydraulic Modelling – Upper Town Burn

Highly modified
Wholly culverted
CCTV survey
InfoWorks Modelling
Draining assessment
Outputs for 1D/2D

7

MH9W

1 3 6

MH9V

2 2

MH9U

3

MH9T

3 3 3

MH9S

4 3

MH9R

4 5 2

MH9Q

5

MH9P MH9N

5 6 2 6 2 8

MH9J

7 6 2

MH9L

8 9 8 9 9 1 3 4 1 6 2 1 1 4 2 1 2 2 1 2 8 51 3 7 1 3 4 3 M H 9 X 3 6 .7 4 5 M H 9 W 3 3 .8 6 5 M H 9 V 2 5 .6 2 3 M H 9 U 1 9 .3 1 M H 9 T 1 6 .5 1 3 M H 9 S 1 6 .3 1 2 M H 9 R 1 6 .4 3 4 M H 9 Q 1 6 .4 6 4 M H 9 P

M

H 9 N

M

H 9 J

M

H 9 K 1 5 .1 9 M H 9 L 1 4 .4 8 4 5 5 9 9 9 1 1 4 .8 2 6 5 9 9 1 1 3 .5 6 6 5 9 1 8 4 1 3 .0 7 9

1

3 .2 8 M H 1 4 1 2 .9 9 3 6 6 2 5 1 3 .2 5 5

1

2 .2 5

M

H 9 X .1 3 7 5 3 4 .9 2 9 .9 9 .4 7 1 M H 9 W .1 3 7 5 2 9 .9 9 2 3 .2 9 .5 6 7 M H 9 V .1 3 7 5 2 3 .2 9 1 6 .6 5 .4 9 7 M H 9 U .1 4 5 1 6 .6 5 1 4 .3 8 .4 8 6 M H 9 T .1 6 1 4 .3 8 1 3 .8 6 .7 6 9 M H 9 S .1 7 5 1 3 .8 6 1 3 .4 3 .7 4 9 M H 9 R .1 7 5 1 3 .4 3 1 3 .2 6 .6 M H 9 Q .1 7 5 1 3 .2 6 1 3 .0 4 .7 4 3

M

H 9 N .1 7 5 1 2 .8 8 1 2 .7 9 .4 3 4

9
9

1 2 .7 1 6 1 2 .5 1 1 .1 6 3 M H 9 K .1 9 1 2 .4 1 1 1 .9 6 5 1 .0 6 M H 9 L .1 9 1 1 .9 6 5 1 1 .8 2 1 .0 6 5 5 9 9 9 1 .1 1 5 1 1 .8 2 1 1 .3 8 1 .8 2 7 6 5 9 9 1 .1 1 2 1 1 .3 8 1 .6 7 2 .6 8 3

6

5 9 1 8 1 9 .1 1 2 1 .6 5 9 1 .2 6 7 2 .6 6 1 M H 1 4 .1 1 2 1 .2 6 7 1 .1 5 1 .7 3 2 6 6 2 5 .1 1 4 1 .1 5 9 .9 7 2 .9 5 1

1

2

N
d

e g ro u n d (m A D ) L in k wid th (m m ) u s in v (m A D ) d s in v (m A D ) p fc (m 3 /s) m AD 9 .0 3 7 .0 1 1 .0 1 3 .0 1 5 .0 1 7 .0 1 9 .0 2 1 .0 2 3 .0 2 5 .0 2 7 .0 2 9 .0 3 1 .0 3 3 .0 3 5 .0 m

Upper Town Burn inlets and profile

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7

Hydraulic Modelling – Upper Town Burn 2D

Detailed topographic survey
Data Processing to get 3D model
MIKE21 HD module
Manhole spills (from InfoWorks)
Assessment of several scenarios and return periods
Appropriate Manning numbers and grid size

3D model and survey data gathered for the Ochtralure area 2D model Ochtralure 1:200 year results

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8

Hydraulic Modelling – Black Stank and Town Burn

Topographic survey
Structures survey
Output from Upper Town Burn IW model
HEC-RAS modelling of both watercourses
Lateral structures definition
Peak flow in Town Burn caused by the

Black Stank

Black Stank Flowing Into Town Burn (B. Eriksen, 2/1/98).

2400 0200 0400 0600 0800 1000 1200 1400 1600 01/01/1999 0.0 0.5 1.0 1.5 2.0 2.5 Plan: final200yr07 River: TownBurn Reach: Upper Town RS: 1020 Time Flow (m3/s) Legend Flow

Town Burn

wn peak

Black Stank caused peak

Town Burn culvert Town Burn 1:200 year predicted hydrograph

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9

Hydraulic Modelling – Black Stank and Town Burn

1:200 year Town Burn and Black Stank combined model results

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10

Hydraulic Modelling – Sheuchan Burn

Topographic survey
CCTV survey
HEC-RAS modelling of Sheuchan A and B
InfoWorks CS modelling of Sheuchan culvert
MIKE21 modelling of Millburn Court manhole spills

Hill c Palm y r Elm Hou This tley c roft Doon gara 3.0m Pos ts Play Area M Ag new Park TCB Pos ts Loch Ryan M e an Low Wa ter Sp ring s FB AGN EW CR ESCENT A 71 8 HILL H EAD Pos ts BM 3.69m E l v e t h a m Pond Glen tilt Ca rrai g Ulid ia Ben v ie Pos ts Lifeboat Station Sand San d an d Sh ing l e San d an d Sh ingl e Cairn sm

re

3.0m 18.9m Sta El Sub Thornfield Av alon BACK RAMPART Depot D e p

t

BM 22.10m Linden Hous e Hall 20.7m Lam arton Sheuc h an Co tt Mans e Park Hous e The High Kirk

f Stranraer

L E S W A L T H I G H R O A D Cemetery P

i

n t B r e e z e BM 13.43m Caribe Sheuc han Cemetery HILL H EAD Rhov an ian Lodge LB Lady Stewart Park Sand and Boulders El Su b Sta S c a u r b a n k Glen

rc h

y Seaforth Waters Edge A R R A N T H O R N B A N K R O A D WEST EN D T ER RACE B 7 3 7 CO URT Seapark Hawk s worth Ry anbank Birc hwood The Moorings Thornbank A 71 8 2.7m Slipway Sand BM 3.51m Pos ts 16.5m San d an d Sh ingl e Hann ay 's H i ll B R O A D S T O N E R O A D Bria rbrae She a r- wate r Dunc liffe Clairmont Rav enna Whin latter High Thornbank M u i z e n b e r g Wes trig Knoc k h aar Cu il

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nn HAWTHOR N ROAD Rya nle a Flo atd ale G len O ter MS Loc hlea Nor-Is le Cra m

nd

Dunm

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11.0 m BM 13.04m Bryn Cluden W e s t l a n d s Ki n garth Rav els ton Craigleac h Fai rfie ld Dunk el d Robi n Hil l Farha Brai dwood Sea forth Greenm ount Sc otby White Hous e Tigh-na-Mara Fe nc e End Birc hgro v e C r a i g a t h e r i e L u y a Ston ele igh W H I T E H O U S E R O A D C H U R C H I L L A V E N U E Am bles S a n M a r c

Lorien

Chip s te ad Kil m ory Carnro se Rath larg L ARG RO AD Wi n db Wil lowcroft Canis bay B r a e f i e l d The Firs El S u b S t a LARG AVENUE L y n d a l e Kas am a Glenk ens D

r

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n

Dalry Craig

c

h Ly m p hoy Garage Arkl et 16 .5m G l e n i f f e r Wk s 19.5m El Sub Sta LESWAL T ROAD M E A D O W B A N K D A L E C R E S C E N T M AYF IEL D AVENUE Ros s ern Englec ot 22.9m HILL H EAD Falhaa r B 73 7 E l S u b S t a Enc liffe The Stables ENCLIFFE LANE Kinneil Wi n darra 17.1m Woodlea BM 20.7 9m Q U E E N ' S Pos t Om ega Linden PARK LANE M e an H i gh Wate r Sprin gs El Sub Sta Pos ts F O R E L A N D P L A C E S w a n I n n (PH) H a m i l t

n

C

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r t FB Sand and Shingle Spreads Pic nic M illh ous e Loc hend M i llb urn Court Villa Area S H E U C H A N S T R E E T Is s ues Und 6.7m Car Pa rk Kinty re Court W I L L O W D E N E C R E S C E N T Ps 14.9m Bowling Green BM 9.32 m 1 1 . 9 m 3.7 m P Sea ban k Cotta ge Lo ch e n d As hgrov e Bun gal

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Sheuc han PO High fie ld H

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p a r k D a r r

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Park hea d She ena A n c h

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l e a Durle y C a s t r a m

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a Green Gates C l u b By t

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Glen Flo ra Laing Hous e Crail

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h Hawthorn Bank M ingary Sandy way s Craigallen Colin da F

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r t r e e s Seabank Hous e Prim ary Sc hool RAND OLPH L ANE Ps AILSA C RESCENT FINNART CRESCEN T B 73 7 F O U N D R Y L A N E L E S W A L T H I G H R O A D D A L R I A D A A V E N U E M I LLFI ELD AVENUE S E A B A N K R O A D 21 .3m T C B LB 1 . 7 m RO W AN ' S HIL L OAKLAND AVENU E LIDDESDALE ROAD SPRING W ELL ROAD F I N N A R T C R E S LIDDESDALE ENT BM 19.62m A V E N U E R O A D C R A I G L E A A V E N U E W h i t e c r

f

t Pen Hill Bon a Vis ta Seaforth Nurs ery Li ndu m Craig loch Buk it Oran g A b e r F a w n m

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e Wilton Dean Dunry an M illeur Eldon Trentham Lis m ore Lintrathen Am bles ide Ham el a nd Saa rme n Du ns c a ith Gle n is l a Cles trai n Ly n ai re Kilv ern C a i r n v i e w C R Penry an C h e r r y b a n k W i n d r u s h Colarn L a d

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v e n Rowan s Hil l Raymed e S t r a t h m

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e Torv aig O AKLAND W O O D L A N D R O A D W I L L O W B A N K H A Z E L G R O V E LAUREL GROVE NUR SERY AVENUE BM 20.3 7m 18 .0m BEECHWO OD AVENUE S E 8.2m Inc hyra Windarra Anmaro Melita Chirma Glen s hi el Ward Bdy MI LLBANK ROAD El Sub Sta Ty rol CO RSEWAL L CRESCENT Sheuc han Bridge BRO OKFI ELD CR ESCENT LEAFI ELD Drain B r a n d e l h

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Da im ar Homeland R O W A N ' S H I L L C R E S C E N T LB Brae Avo n Be ith Heugh SPRING BAN K R OAD Cov ington Glenes k Sink s Win dy ri dg e Drum j arg

n

El Su b Sta W O O D L A N D RO AD Northbrae Glengorm Caladh Glas mont L a n g d a l e Sil v erd ale Tay pa rk Duffryn Fai rm i l e Inverl eith Torc ross Fren ch w o

d

Fai c a n Rubi s l aw Wem y s s M y m e n s i n g h Karo ri M a rnoc h Kin m ou nt Drum log an Lo ch Bank Aod ain n Craig na i r Rowan brae Sib bal dbie Auc hen git h T h e A n c h

r

a g e T h e S h e i l i n g M i lha v e n M e a l l a n Carnbo M arc h Rang i to to Sannox Keldeen As c og Holm s l ey Ails a She rbroo k e Liddes dale Hous e Lidd es dale Cottage Bungalow Liddes dale THE GRO VE BRO O KFI ELD AVENU E BRO OKFI ELD CR ESCENT Burn sid e L E A F I E L D WOOD L AN D ROAD RISE Drain Drain Aarh ause Ceud M ile Failte LIDDESDALE ROAD SPRING BAN K R OAD L E A F I E L D Is s ues Sink s Sink s Is s ues Springbank Cottage Is s ues Springbank Springb ank Is s ues Mas t Collec ts Is s ues Trac k Pond Is s ues y

Spring Bank Road Bridge Liddesdale Farm Structure 676 Structure 503 Legend

Water Depths (m) 3.5 0.7 0.2 0.01 Masonry culvert Tw in pipe culvert Main rectangular culvert

Sheuchan Burn area Sheuchan Burn 1:200 year results

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11

Hydraulic Modelling – Laundry Burn

CCTV survey
Totally culverted
Discharging into

the Town Burn

Reported capacity issues
No flooding predicted
Blockage issues

Laundry Burn location and 1:200 year profile

SLIDE 13

12

Wide Stranraer Results

Stranraer 1:200 year floodplain outline

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13

Benefit / cost analysis

Economic performance of flood protections schemes
Benefits are measured in terms of the present value of damages avoided
ver the life of the scheme.
Eight Flood Alleviation Schemes (FAS) identified through Stranraer Flood

Study.

For each FAS the following was considered in the modelling exercise:
Do nothing (current situation modelling results)
Do minimum
Do something (option modelling)

SLIDE 15

14

Stranraer Flood Alleviation Schemes (FAS)

Sand Bi g Pl ant at i

n

Bl ackpar ks I ndust r i al Est at e St ranraer Academ y Loch R yan Sand Loch R yan Loch R yan O cht r el ur e

Black Stank Black Stank Town Burn Laundry Burn Town Burn Sheuchan Burn Sheuchan Burn FAS-7: Localised Bunding FAS-6: Town Burn Railway Culvert FAS-8: Black Stank Mouth Diversion FAS-2: Upper Sheuchan FAS-3: Thorney Croft Inlet FAS-4: Ochtralure Inlet FAS-5: Stoneykirk Roundabout FAS-1: Sheuchan Outfall

Legend

Watercourse Predicted Floodplain Historical Flooding Flood Alleviation Scheme Option

Stranraer FAS areas

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15

Stranraer Main Causes of Flooding

Insufficient hydraulic capacity of culverts and inlets
Blocking issues in culverts and inlets.
Overland flow
Structural issues
Highly modified watercourses

Town Burn Downstream of Railway Culvert

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16

FAS 1 and 2 – Sheuchan Outfall and Upper Sheuchan Burn

FAS 1 associated with flooding in lower Sheuchan due to lack of capacity
Structural issues
New Outfall designed.
FAS 2 concerned with flooding along properties in Upper Sheuchan
Localised protection is the preferable option.

Sheuchan Outfall location and profile

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17

FAS 3, 4 and 5 – Upper Town Burn

FAS 3 is associated with flooding in Thorney Croft Inlet whereas FAS 4 is

associated with Gallowhill Rise and Highcroft inlets

Inlets improvements is FAS 3 most practical solutions
Channel diversion is FAS 4 preferable option
FAS 5 concerned with flooding in StoneyKirk Roundabout
Structural and hydraulic capacity issues.
Replacement not viable

FAS 4 diversion location and profile

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18

FAS 6 - Town Burn Railway Culvert (Black Stank and Lower Town Burn)

FAS 6 associated with flooding in the Station Road area (Town Burn)
Flooding caused by the Black Stank and Town Burn interaction
Poor culvert condition – Flow restriction
Replacement of the railway culvert by a 750mm flow control
Modifications further downstream

Town Burn Railway Culvert

SLIDE 20

19

FAS 7 and 8

FAS 7 associated with flooding in properties along the Black Stank
Localised protection proved to be the preferable option
FAS 8 concerned with alleviating flooding in the vicinity of properties at the

downstream end of the Black Stank

Diversion of the Black Stank peak flows

FAS 8 diversion option

12 25 39 16 14 BURN SI D E TERR ACE Bishop Burn BM 4.3 3 m Denv er Cairnv iew Hi -Lite Forfield Court Loc hv iew Hous e 23 1 24 11 8 1 3 Bis hop Burn Bridg e R E P H A D C R E S C E N T L O C K V I E W R O A D L O C H V I E W C R E S 2 Chev ron 1 3 15 2 3 2 14 2a 2 b Ay re Mira 1 5 11 1 4 5 8 M are Auld Kil don an Bis hop Burn Cotts 1 2 1 7 9 Auchl a nd

Route A Option 2 - Excess Flow

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Stranraer Discarded Options

Sand Bi g Pl ant at i

n

Bl ackpar ks I ndust r i al E st at e St r anr aer A cademy Loch R yan Sand Loch R yan Loch R yan O cht r el ur e

Black Stank Black Stank Town Burn Laundry Burn Town Burn Sheuchan Burn Sheuchan Burn

Outfall Diversions Culvert Replacement Culvert Improvements Storage Storage Black Stank & Town Burn Connector Channel Railway Overflow Cacthment Diversion to Ballyferry Burn Open Section Culverted Storage Storage Pipe Upsizing Channel Realignment Culvert Replacement Channel Realignment Storage

Legend

Watercourse Surface water pipe Foul or Combined pipe Discarded Option

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21

Stranraer Preferable Options

Sand B i g P l ant at i

n

Bl ackpar ks I ndust r i al Est at e St r anr aer A cademy Loch R yan Sand Loch R yan Loch R yan O cht r el ur e

Black Stank Black Stank Town Burn Laundry Burn Town Burn Sheuchan Burn Sheuchan Burn

FAS-8: Black Stank Outfall Diversion FAS-7: Black Stank Bunding FAS-6: Railway Culvert FAS-5: Stoneykirk Roundabout Culverts FAS-4: Ochtralure Diversion FAS-1: Sheuchan New Outfall FAS-3: Thorney Croft Inlet Improvements FAS-2: Upper Sheuchan Bunding

Legend

Watercourse Surface water pipe Foul or Combined pipe Discarded Option

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Summary and Conclusions

A high level detail modelling identified properties at risk in Stranraer
Water depths were predicted at those properties
Eight flood alleviation schemes were assessed
Potential mitigation options were tested
A benefit/cost analysis approach was used
The diversion type option was the most viable for three FAS
Culvert or inlet improvements was the preferable options for other three FAS
Local bunding was the option chosen for two FAS