Stranraer Flood Protection Scheme: A case Study Juan Fernandez, Simon McGee, Alasdair Fraser Mouchel 4th International Symposium on Flood Defence: The Beta Centre Managing Flood Risk, Reliability and Vulnerability Stirling University Innovation Park Toronto, Ontario, Canada, May 6-8, 2008 Stirling, FK9 4NF Scotland, UK 0 Introduction - 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 1 Stranraer Watercourses - Black Stank -Town Burn - Laundry Burn - Sheuchan Burn - Surface water sewers Stranraer watercourses 2 Data Gathering -Site visits - Topographic survey - Watercourse survey - Floodplain survey - Structural survey -3D survey - CCTV survey - DAP survey - Manhole survey Stranraer topography - Pumping Station survey - CCTV survey -CSO survey Stills from Millburn Court CCTV Survey (John Bunting, EEC - 7 July 2005) 3 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 Extreme water Return Period (year) 2.33 5 10 25 50 100 200 500 (years) level (m AOD) Black Stank 3.16 4.38 5.24 6.66 7.83 8.98 10.35 12.48 1 2.65 Town Burn 1.26 1.62 1.88 2.22 2.4 2.53 2.65 2.81 10 3.00 Reach B 1.09 1.58 1.89 2.34 2.81 3.27 3.82 4.68 25 3.14 Sheuchan Burn Reach A 1.06 1.57 1.89 2.36 2.75 3.21 3.77 4.63 50 3.23 Whole 2.5 3.66 4.39 5.46 6.42 7.51 8.78 10.76 100 3.38 Laundry Burn 1.22 1.82 2.21 2.77 3.26 3.73 4.37 5.35 250 3.52 Estimated Peak Flows (m3/s) for Stranraer Watercourses Extreme Water Levels for Stranraer 4 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 5 Hydraulic Modelling – Upper Town Burn - Highly modified - Wholly culverted - CCTV survey - InfoWorks Modelling - Draining assessment - Outputs for 1D/2D 37.0 35.0 33.0 31.0 29.0 27.0 25.0 23.0 m AD 21.0 19.0 17.0 15.0 13.0 11.0 MH9N MH9J MH9L MH9W MH9V MH9U MH9T MH9S MH9R MH9Q MH9P 9.0 m 70 136 220 300 333 403 452 500 562 628 762 809 899 1034 1062 1142 1220 12851307 1343 Link MH9X.1 MH9W.1 MH9V.1 MH9U.1 MH9T.1 MH9S.1 MH9R.1 MH9Q.1 - MH9N.1 - - MH9K.1 MH9L.1 05599901.1 06590901.1 - - 06591819.1 MH14.1 06602005.1 - - - - width (mm) 375 375 375 450 600 750 750 750 - 750 900 900 900 900 1050 1200 - - 1200 1200 1400 1200 - - - us inv (m AD) 34.900 29.990 23.290 16.650 14.380 13.860 13.430 13.260 - 12.880 - 12.716 12.410 11.965 11.802 11.380 - - 10.659 10.267 10.105 - - - - ds inv (m AD) 29.990 23.290 16.650 14.380 13.860 13.430 13.260 13.040 - 12.790 - 12.510 11.965 11.802 11.380 10.670 - - 10.267 10.105 9.970 - - - - pf c (m3/s) 0.471 0.567 0.497 0.486 0.769 0.749 0.600 0.743 - 0.434 - 1.163 1.060 1.060 1.827 2.683 - - 2.661 1.732 2.951 - - - - Node MH9X MH9W MH9V MH9U MH9T MH9S MH9R MH9Q MH9PMH9N - - MH9J MH9K MH9L 05599901 06590901 06591804 - - MH14 06602005 - - - - ground (m AD) 36.745 33.865 25.623 19.310 16.513 16.312 16.434 16.464 - - - - - 15.190 14.484 14.802 13.560 13.079 - 13.280 12.993 13.255 12.250 - - - 6 Upper Town Burn inlets and profile Hydraulic Modelling – Upper Town Burn 2D -Detailed topographic survey -Data Processing to get 3D model 3D model and survey data gathered for the Ochtralure area -MIKE21 HD module -Manhole spills (from InfoWorks) -Assessment of several scenarios and return periods -Appropriate Manning numbers and grid size 2D model Ochtralure 1:200 year results 7 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 Town Burn Black Stank Black Stank Flowing Into Town Burn (B. Eriksen, 2/1/98). own peak caused peak Plan: final200yr07 River: TownBurn Reach: Upper Town RS: 1020 2.5 Legend Flow 2.0 1.5 Flow (m3/s) Flow 1.0 0.5 0.0 2400 0200 0400 0600 0800 1000 1200 1400 1600 01/01/1999 Time Town Burn 1:200 year predicted hydrograph Town Burn culvert 8 Hydraulic Modelling – Black Stank and Town Burn 1:200 year Town Burn and Black Stank combined model results 9 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 b Bi The Firs d r n ch i gr Cr ov Fence End Ro s s e rn W D a e Greenmount l a i t A ga Sc otby 22.9m E S th e d O r b ie u a R e W Englecot S t B G i ll r s o Ha wk s wo rt h a p R w L ef i c A ie A r ld h o Lorien R L ft G C W A H Sand V St IT E o n E NU e l H E eig OU White House h SE Tigh-na-Mara Canisbay K L u R ilm ya O o Ambles AD Ryanbank R ry a t hla rg Legend Ca Sa r C n nr H M os U ar Birchwood e RC c o B HI r L L aid A High Thornbank Sl ipway w VE Water Depths (m) o o N The Moorings 19.5m L d U ym E Cluden ph o y Se Farha afo rt BM 3.51m C h ra igo ch R Thornbank il l Da o b H 3.5 l in ' s ry H Whinlatter ay ill nn Ha D Du n c l i f fe or ys s t B on Ka d Pos ts s am a n R 0.7 a O l S t Knockhaar 16.5m s A a n e D d Westrig S W Ravenna S T a h O n Glenkens w e d M C M a a N E h u u E S L t i H i t r 0.2 l- z - A E r F A e e h D S io W n r R i O W a n be n W n T r O g B A g HO g B A LT n R A le N R i N ri D K O K R a A O Clairmont rb D A r F D a a e 0.01 ir f ield Lochlea D G 1 A l Ga ra g e 6. e 5 O m n y R o r 0 K c No r-Is l e h Craigleach N y Sand and Boulders A 2.7m B e r N o R Wks m O n C H W ra u E t m D T ST r o E le e n N k f d D r f TE Masonry culvert i R M A n R A e AC Y l E F G MS IE e L al Loch Ryan D d BM 13.04m A n V y E L 11.0m Tw in pipe culvert N U n y E r B n t o Seaforth s l A 7 e 18 v a ld Waters r Main rectangular culvert R e k e 7 ea t 3 Edge n l e l 7 D u n O A a a n L D d B S E y t e l c C R oa a El RE l G u S F rb Sub C a EN n Sta T k E l S u N b T A Seapark R S R t U a R T A O H C E d LB n G U R O V C E O 6.7m RSE Pond WA LL CRE SCE NT Kinty re C a r Court P ar Issues k Si nk s El Sub Sta Sheuchan Bridge Glenesk Pi c ni c Sand and Shingle Northbrae Covington MILLBANK ROAD Area Glengorm Ca l a d h Co l l e c ts Gl a s m o n t l e gda M an B Liddesdale Cottage L il l R C bu Issues Spreads O o r u n FB Liddesdale House R O rt u e K b l F Sannox rda is e IE ood ilv T w la S L nch a W S re M F w D y h p a B B e C a e I a r Keldeen r R n r d R R S n b k v O O B H L r e E E o o d Lochend O O r U w o le S y D K k K C C As c og i Vil la W u F e F F t T E H h f a IE IE o L a f C A t N ILLOWDEN E e r W R M Liddesdale Farm L L N r o ic y T E Millhouse r c c K n S H D r a D C S e S o h n i a p o n E T C A r s m N R n i l s F T n m R V E H g o a s E E s E ig u ir k N n T le n 8.2m m Liddesdale S h M a y U t e K C L b Bungalow D il a ag W R y a e o E E B e t m r c t a r u u S a N h o o M n Seabank t n e r m C T g e n i n e IL r g l D a d House i s o A L i lo S t O o n g F w R p t a K C o g M IE h n N R r A D L i B n a A G D g r N n I L R s P Tyrol R A L Co l i n d a Wemyss o S I A V y c A n s Ai ls a h e D E re v A a rt o N ou n A U ir F e B V E Craigallen e E i Ch i rm a N PO th U ir E a R n o F g S i i w O b a a D R r b Heugh A C a n Penryan E C b Brae RO r A ld L K a r N MingaryHa wth o rn L u b a E la in A i S nis a B lo A c i e e str A N h e R I C W Gl e SE Bank c n Cl h D e O c h A nd n h e L l a Sandyways g W y r T e Laing ts P A r r a m os L i a y H H n P th N b e A a IG arm Ho u s e 3 n a C 'S k H S .