Th a m es W a t e r River s Di vi s i on KENNET VALLEY STUDY • READING - THEALE F i n a l Re p or t • J u n e 19 8 7 • • • • • • SIR ALEXANDER GI BB & PARTNERS i n a ss oc i a t i on wi t h I NSTITUTE OF HYDROLOGY • T h a mes W a t er • R iver s Div i s i on KENNET VALLEY STUDY . READING - THEALE F i n a l Rep or t • J u n e 198 7 • • • • • • • SI R ALEXANDER GI BB & PARTNERS in a s soci a t i on wi t h I NSTITUTE OF HYDROLOGY • S I R A L EXA ND E R G I B B & PA RT N ER S EA RLEY HO US E C O N S U L T I N G E N G I N E E R S 4 27 LO N DO N ROA D EA RLEY P • R T N E R S • S E N I O R C O N S U L T A N T S R EADI NG RG6 IB L 0 14 C O AT E S W M • E• • n c t F. S • N on g • 0 15S E • • s C E K P . S C O TT m c r En n o t n o E N Z L L L L L L o w l 0 7 3 4 - 0 10 6 1 ( I S L I N E S ) v C O R N ET m• n e e r i B . N O R R i S / I C E eA s C E p , A . A . B A C K IIIS S D o m, • Ic t • EL EO P L I. E. 0 113 B O S O R W A R E • O I N G A . R M U R R AY o f t • C E 0 .18 0 6 1 J D H E N N E S S Y N A B C C N o n T A/ 0 0 0 5 B A L LA R D S A FLEE oN N ES • S S O C I AT E S p p II • ED 0 7 3 4 . 6 4 0 8 0 J . P . K E N T N • B C E R . A , C R O W • • IN A N D A T J . IS B O W C O C K ma. • 10 E Y• S C E W , 0 . P 1R I E 7 21 B U C KI N G H A M G A T E • a 0 • (DA W S O N • k in c E w on t : • I N I 0 , J B R I C E • S • r i c e M . P . H . M A R T Ol t 14, C E mi r e ] O J . • N I G H T r • ' I C E W E S T M I N S T E R S W 1E 6 P E 0 . 0 , K N O T T • • - M E L L L L L L O N E 0 1. 2 2 2 s t n i ( 2 L I N E S ) P . T . M • C R E I G H T N A /NE E J . S . A AA A A • 114 • 10 E FIN ES • I O N E C O N S U L T T T T T et P . N • R R I S N I C E • I N• • • E J . D A V I E l a c Pi t t w o r n 11 G . SA VI C E W . T . m E E 1154 N E E H R . T O M S O N 13• • • A A A A A FI C • C R T O E . 0 , P A G E R B I Pi t t • e n• R , C H A P L O W Ci . • . 1:1 mi tk e • J . C . T U R N B U L L B C E ma n R . S t . H . C O X O a MI C E N IS • Av e • E JBCL/WAE/86680A • 0 . L . W I L D E R IN G E • Im cc .. E J • . K E L L E H E R • I C E T . 0 . C • R P IEN T E R OA r et t J A . C . D A V ID S O N e s • mi c e A . a . W 0 0 0 10 11 1) e f t I IC E B o n • 4 1.H E R I . C . 0 0 5 N ET • 1 A A A A A • I N T M . T . H . K I M M I N S IN S A AND Y 22nd June 1987 C . J . M . N I P P E R m• B C E AN N ? ...a c t Thames Water , Rivers Div ision , Nugent House , • Vastern Road , Read ing , Berks . For the attention of Mr . G .P .G . Johnson • Dear Sirs , KENNET VA LLEY STUDY - READING - THEA LE F INAL REPO RT 9 We have p lea sure in enclo sing six copies o f the Final Repo rt . The methodo logy deve lope d for the study represents an unusua l ap proach to flood studies which has been tailored to the av ailab le reco rd s o f hydrometric measurements and historic flood s . It has enabled an ev aluation to be m ade o f the sensitivity o f flooding to changes in flood 9 p la in storage without recou rse to mathem atica l mode lling . The techniques developed for computing flood p lain storage and mode lling the flood routing m ay well be app licab le to other ca tchments whe re sim i lar ev aluations are required , particularly if more hydrometr ic data is availab le . The com puterised ca lculation of sto rage volum es with in the Kenne t Va lley may a lso be o f use in evaluating the net changes resulting from deve lopm ent proposa ls . • We shall be p leased to assist with any fu rthe r investigations th at you require . If there is any matter that requ ires cla rifica tion in this present repo rt p lease do no t he sitate to con tact us . • Yours faith fully , for S IR ALEXA IBB PA RTNERS • • • • KENNET VALLE Y STUDY FINAL REPORT TABLE OF CONTENTS • Page No . EXEC UT IVE SUMMAR Y 1 , INTRODUCT ION • 1 .1 Ob jectives o f the study 1-1 1 .2 Methodo logy 1-3 1 .3 Scope of the repo rt 1-5 DATA BA SE • 2 .1 Study area 2- 1 2 .2 Survey 2-4 2 .3 Mapping and aerial photography 2-6 2 .4 Flood records 2-6 2 .5 Site reconna issanc e 2-8 • HYDROLOG Y 3 .1 Introduction 3- 1 3 .2 Catchment cha racteristics 3- 1 3 .3 Unit hydrog raph ana lysis for Kennet at Theale 3-8 • 3 .4 Flood est ima tes for Kennet at Theale 3-9 3 .5 Flood estimates for Foudry at M4 3- 12 3 .6 Flood estimates to County Weir , Reading 3- 13 3 .7 Ana lysis o f June 1971 ev ent 3- 17 3 .8 Ana lysis of Ma rch 1947 ev ent 3- 18 3 .9 D iscussion 3- 19 • 3 .10 Conclus ion 3-20 FLOO D ENVELOPES 4 .1 Approach 4- 1 4 .2 Storage during 1971 flood 4- 2 • 4 .3 Storage for other events 4- 7 4 .4 Chang es in the flood pla in 4-9 4 .5 Flood envelopes 4- 16 H ISTOR ICAL DEVELOPMENT IN THE STUDY AREA • 5 .1 Rev iew o f plann ing docum enta tion 5- 1 5 .2 G ravel ex trac tion 5- 6 5 .3 Waste dispo sal and lan dfill 5- 10 5 .4 Res idential and industrial development 5-10 I • Referenc es • • Annexe A L ist of docum en ta t ion Annexe B Report on 197 1 flood Annex e C Hy drology , Ap pend ices 1 to 5 • • LIST OF TABLES Table 2 .1 Floo d Levels 2- 7 • • • • • • • L IST OF FIGURES • Figure 1.1 Study a rea 1 - 2 Figure 1 .2 Catchm ent area 1 - 3 F igure 2 .1 Plan o f structures In pocket Figure 2 .2 Area of surv ey and cross sections In pock et Figure 2 .3 Ex tent of 1971 flood and recorded levels In pocket • F igure 3 .1 Catchm ent plan 3 - 22 Figure 3 .2 So ils 3 - 23 Figure 3 .3 Princ ipal urban areas 3 - 24 Figure 3 .4 Gauged sub ca tchm ents of th e K ennet 3 - 25 Figu re 3 .5 Compa rison o f Brimpton , Th ea le and Blake 's Lock • limnigraphs - June 1971 3 - 26 Figure 3 .6 Unit hy drographs for Ken net at Thea le 3 - 27 Figure 3 .7 Flood frequency curves for Kennet at Th eale - sta tistica l 3 - 28 F igure 3 .8 Flood frequency curves for Kennet at Theale - ado pted 3 - 29 Figure 3 .9 Des ign Hydrograph s - Kennet at Theale 3 - 29 Figure 3 .10 Flood frequency est imates - Foudry at M4 3 - 30 Figure 3 .11 Design hy drographs - Foudry at 1(4 3 - 30 Figure 3 .12 Comb ined catchm ent to floo d pla in - in flow and outflow 3 - 31 Figure 3 .13 Inundation volume frequency - Kennet flood plain 3 - 31 Figure 3 .14 Observed and simu lated Thea le flows - June 197 1 3 - 32 Figure 3 .15 Da ily ra in falls (mm ) - 10 June 1971 3 - 33 F igure 3 .16 Nota ble 1, 2 , 4 and 8 day ra in falls in th e Kennet catchm ent 3 - 34 Figure 4 .1 1/5000 maps sheet 1 o f 4 In poc ket Figure 4 .2 1/5000 ma ps sheet 2 o f 4 In pocket Figure 4 .3 1/5000 maps sheet 3 o f 4 In pocket Figure 4 .4 1/5000 maps sheet 4 o f 4 In po cket Figure 4 .5 Flood env elopes 1/10000 In pocket Figure 5 .1 Gravel ex traction and open water area Pull-out , back of report Figure 5 .2 In filling after grav el extraction Pull-out , back o f report Figure 5 .2 Kennet Va lley Plan Proposa ls 5 - 4 F igure 5 .4 Ta rmac proposa ls for Holy Brook and Coley Mea dows 5 - 9 Figure 5 .5 Ax iom 4 Development 5 - 12 Figure 5 .6 ARC long term proposa ls for study area 5 - 14 Figure 6 .1 Flood pla in zones - exam ple 6 - 5 Figure 6 .2 Backwater ana ly sis 6 - 10 Figure 7 .1 Flood route th rough gravel pits 7 - 3 Figure 7 .2 Diversion ov er weir 7 - 5 Figure 7 .3 Modifications to hydrogra ph 7 - 7 • • EXECUTIVE SUMMARY 1.