1998 Easter Floods Final assessment by the Independent Review Team – Volume 2 Product code: GEHO0807BNAZ-E-E EASTER 1998 FLOODS VOLUME II INCIDENT REPORTS Prepared by the Environment Agency 011 behalf of the Easter Flood Review Team September 1998 I CONTENTS Page No INTRODUCTION 6 2. SPECIAL STUDY SITES 7 2.1 NORTHAMPTON (AN(;UAN REGION) 7 Map of Northampton 25 Fig 2.2 Localion Map 26 Fig 3. 1 I)efence ResponsihiIi tv plan 27 Fig 3.2 Extent ol Flooding map 28 2.2 LEAMINGTON SPA, M11)LANDS REGION) 29 Map of Learninglon Spa 33 :2.2 K1J)LINGTON (THAMES REGiON) 34 Map of Kidlington 48 I 981 Land Drainage Rye law Map 49 2.3 SKENFRITH (ENVIRONMENTAGENCY WALES) 50 Map of Skenfrith 56 Fig 1 Location Plan Map 57 Fig 2 Historic Flooded Area Map 58 Fig 3 Historic Flood Pattern Map 59 Fig 4 Surface Water Drainage Map 60 Fig 5 Dec 1979 Flood Photographs 61 -65 Fig 6 Flood Records at Skenfrith Corn Mill 66 3. INCIDENT REPORTS 67 Plan of the Environment Agency Regions 68 3.1 AN(;UAN RE(;ION 69 Plans of Catehrnents Affected 70 Northern Area 71 I)iaerarns 01 Flood Events and Flood Warnings 7277 Hi lii ng Aquadrorne. Northaniptonshire. River Nenc 7$ ( ed di nglon. Northarnptonshire. Rivet lsc $ I KisI inghurv. Non haniptonslnre..River Nenc $5 Pctcrhorough. River Nenc $9 lhrupslon Islip, Northamptonshire, River Nene 93 Wanslord, (amNride.eshire, River Nene 97 Wecdon, Northamptonshire. River Nenc 100 Wel linghorough Northamptonshire, River Ise 104 Central Area 108 Diagrams of' Flood livents and Flood Warnings 109—I 14 'The Alconhurvs. Great Ouse (Upper) 115 Iedord, Greai Ouse (Upper) 119 Buckinghani, Great Ouse (Upper) 123 (lapharn, GreatOuse (Upper) 126 Ilen'inglords, Great ()use (Upper) 129 Newport Pagnell. Great Ouse (Upper) 133 Si 1es, Great Ouse (Upper) 137 St Neots, Great Ouse (Upper) 141 Stony Stratford. Great Ouse (Upper) 145 Iowcester, River love 148 3.2 MII)LANDS REGION 151 Plan of' CatchrnentsAffected 152 per Severn Area 153 Diagrams of Flood Events and Flood Warnings 1 54-155 Blanquettes Estate, Worcester, Barbourne Brook 156 Cradley/Leigh Brook, Worcestershire 159 Lower Severn Area 161 Diagrams of Hood Evenls and Flood Warnings 162-171 Alcester, Warwickshire, River Avon 172 i3arford, Warwickshire, River Avon 174 l3roorn. Warwickshire, River Arrow I 76 Caravan Sites within the Warwickshire Avon Catchment 178 Evesharn,Worcestershire, River Avon 183 Ilimbleton. Worcestershire,I3ow Brook 186 Littleton, Worcestershire,,I3adsey Brook 188 long lichingion, Warwickshire,River lichen I 9() Marton, Warwickshire. River Learn 1 92 Pershore, Worcestershire. River Avon 1 Sedgeherrow,\Vorceslershirc River l'.bournc I % Slnp1on—on—Stour.Warwicksh ire. River Stour 1 )8 Soutfiain, Warwickshire. River ltchen 200 Stratford-Upon-Avon Warwickshire, River Avon 202 icwkeshurv, (floucestershire, River Severn 204 Iredington.Warwicksliire. River Siour 206 Warwick, Warwickshire, River Avon 208 Welh rd—( )n—Avon, Warwickshire, River Avon 210 Wel leshourne, Warwicksh ire, River Dene 212 Winchcomhe, ( doucestershire, River Ishourne 2 14 LowerTint Area 216 Diagrams of Flood Eventsand FloodWarnings 217-222 Asfordby,Leicestershire. River Wreake 223 Barrow-Upon-Soar. Leicestershire, River Soar 225 Cossington, Leicestershire, River Soar 227 Frisbyon the Wreake to Rateliffeon the Wreake. 229 Leicestershire. River Wreake Melton Mowbray, Leicestershire, RiverWreake 231 Sileby. Leicestershire. Sileby Brook 234 Whatton and Aslockton, Nottinghamshire, River Smite 236 Zouch, Near Kegworth, Leicestershire, River Soar 238 3.3 THAMES REGION 240 Plan of Catchments Affected 241 Diagrams of Flood Eventsand FloodWarnings 242-243 Adderbury.Oxfordshire, Sor Brook 244 Adderbury 1981 Land Drainage Byelaw Map 246 Banbury, Oxfordshire, River Cherwell 247 Banbury1981 Land Drainage ByelawMap 251 Lslip, Oxfordshire, River Ray 252 Nip 1981 Land Drainage ByeLaw Map 255 Thrupp,Oxfordshire, River Cherwell 255 Thrupp 1981 Land Drainage Byelaw Map 259 3.4 ENVIRONMENTAGENCY WALES 2W) Plans ofCatchments Affected 261 Diagrams of Flood Eventsand Flood Warnings 262-265 The Forge. Osbaston, Monmouth. River Monnow 266 Location Plan Map 269 1 listoric Flooded Area Map 270 Source of FloodingMap 271 Talgarth.Near Brecon. Powys. River Ennig 272 l.ocation PlanMap 276 Flood Plan map 277 River Ennig C'atchmentmap 278 4 4. SUMMARY TABLES 279 4.1 AN(;LIAN REGION 279-302 4.2 MII)LANDS REGION 303-327 4.3 THAMES REGION 329-333 4.4 ENVIRONMENTACENUY WALES 334-33O 5. GLOSSARY OF TERMS 337-341 INTRODUCTION These reports were prepared by the Environment Agency to SUppOrt the work of the Independent Review Team. The Agency was guided by a methodology devised by the Independent Technical Advisor. The Review Team visited the majority of the flood incident sites and has referred to these reports in preparing its assessments for Volume I. 6 2. SPECIAL STUDY SITES 2.1 NORTHAMPTON (ANCLIAN REGION) BackgrouiulInformation General Catchment geography and the physical characteristicsof the river system Northampton is located some 13km east of Daventry and 17km north west of Milton Keynes on the banks ofthe River Nene. This location coincideswith the confluence ofthe River Nene's main tributaries, the Brampton Branch and Kislingbury Branch., There are five catchments which feed the River Nene upstream of Northampton. Upton (Catchment 32006) and St Andrews (Catchment 32007) are large, gauged rural catchments. Catchments 1, 22 and 23 are more urban, ungauged catchments with shorter response times. The catchments are shown on Figure 2. 1. Any other water systems such as canals and reservoirs, the presence or operation of which could have affected flood conditions Water Suppyeservqj_s Thereare three large AnglianWater water supply reservoirs within the catchment ofthe Brampton Branch; Pitsford, Ravensthorpe and Hollowell. Pitsford was constructed in the 1950s while the latter two were constructed at the turn of the century. On the Kislingbury branch there are two smaller British Waterways (BW) reservoirs; Daventry and Drayton, constructed in the 19th century. Flood Stonge Reservoirs There are several smaller flood storage reservoirs within the Northampton Catchments which provide attenuationto development run-off These are located at Duston Reservoir, Jigsaw Lakes, Lake Delapre, 1)allington Brook Reservoir, Wootton Brook, Wootton Fields, Brackmills, and The Lakes, Bedford Road. The standard of protection where known, provided by the reservoirsvaries between a I in 50 and I in 100 year return period. Grand Union Canal The Grand Union Canal is the responsibility of British Waterways. It runs through the Northampton Catchrnent and interconnects with the R. Nene to provide continuous navigation to the R Thames. The canal is served by the two BW reservoirs. The section between the R. Nene at Northampton and Braunston is approximately20 miles long and was constructed in the 18th and 19th centuries. To the north of Braunston it continues to the summit at Foxton Locks near Market Harborough. The Northampton arm of the canal links to the River N1ene navigation in Northampton. 7 Surface Water Systems The responsibility for the surface water system throughout Northampton is shared between the nparian owners, Anglian Water and the Northampton Borough Council. Surface water drains enter the R. Nene via different routes. The northern area drains directly to the R. Nene via storm water outfalls while the southern area can be separated into three discrete elements: 1) the recent and continueddevelopment ofBanbuiy Lane which utilisesthe flood storage capacity in the offline Duston Retention Reservoir. 2) the developmentof Briar Hill which dischargesvia two 1 .2m diameter syphon sewers across the railway line after which they merge into a single I .5m diameter pipe and discharge into the R. Nene at Duston Junction. 3) the developmentof Far Cottondrains eastwards via the Hardingstone Drain on the southern side of Ransome Rd into Lake Delapre and subsequently into the Hardingstone Dyke; and the Hardingstone Dyke which drains from the northern side of Ransome Rd eastwards into the River Nene. Northampton Washlanc The Northampton Washlands,constructed in the I970s, are located downstream ofNorthampton. They are used to mitigate the effect of development in Northampton on the valley downstream without having a detrimental effect upstream. The Washlands are controlled by primary and secondary control sluices and overflow spillways. The Primary Control Sluice consists of three gates. The centre gate is a vertical overflow gate which rises up out ofthe cill. The outer two are vertical underfiow gates. The Secondary Control Sluice is a vertical overflow gate which controls the inlet to the Washlands and opens when water levels reach 55. 15m AOD. A combination of automatic gate movements and resulting storage are used to control the downstream water levels and flows to approx 52.8m AOD and 28 curnec respectively. When storage is fully utilised downstream flows increaseand water levelsrise accordiny Catchment and flood plain environmentalchanges affecting the river and land in and above the flood plain Brampton Branch Above Northampton on the Brampton branch of the Nene, the catchment is rural in character and there has been no major development within the flood plain. Such development as has occurred has generally been small scale residential infill within the villages. The A14 trunk road crosses the northern tip of the catchment and mn-off from this has been mitigated against by balancing. An attenuation reservoir has been constructedon the DallingtonBrook. No major river works have been carried out on this branch since defences were raised in the 1940s. Routine maintenance works consist ofobstruction removal and occasional de-silting. Kislingbui ininch On the Kislingbury branch, the catchment is rural in character although there are a number oflarger villages. Daventryis an expanding urban area at the head ofthe catchment from which increasing run-off has been mitigated against by attenuation within the Daventry and Drayton reservoirs. 8 Completed in the early I 960s approximately25km of the Ml motorway drains unattenuated into the Kislingbury Branch. There is provision to accommodate flood flows where the road is embankedacross the floodplain.