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<br />40 <br />U>O <br /> <br />rA <br /> <br />40u", 40""" <br />w'" <br /> <br /> <br />Y, <br /> <br />4o..e> <br /> <br /> <br />co <br /> <br />Y, <br /> <br />!t, Iou", .1... <br /> <br />-<D <br /> <br />L <br />':g <br />~ ~ <br /> <br />SECTION A-A <br /> <br />----<V <br /> <br />(0) ENCROACHMENT (iF J,lA!~' <br />CHANNEL. ALSO OVERBANK <br />FLOW FORCED IN1Q CHANNEL <br />THROUGH Tl-lE OPENltlG, <br /> <br /> w'" <br />- I <br /> " <br /> , <br /> W" <br />~ J , .~ <br /> '---[~ <br /> Y, <br /> w'" <br /> , <br /> --r <br /> Y, <br /> W" <br />.... I <br /> --r; I I <br /> " <br /> <br />----<V <br /> <br />(b) NO ENCROACHMEtlT OF' MAIN <br />CH"NNEL. aUT O\'[RBANK <br />flOW FORCED INTO CHANt~EL <br />niRQUGH mE OPENING. <br /> <br />----<V <br /> <br />(c) SET BACK FROr..l ,lAIN <br />CHANNEL. BUT STILL $0"-'( <br />OF 'THE OVER8AN~( FLOW <br />1$ fORCED INTO ~HE CHANNEL <br />TllROUGH THE OP :;:NIIIG. <br /> <br />-<D <br /> <br />----<V <br />(0) BRIDGE COt/mACTS S1REAM. <br /> <br />----<V <br />(b) STREAM NARRO'NS. BRIDGE <br />LOCATED AT UPPER END <br />OF N....RRQWS. <br /> <br />----<V <br />(c) S7?:E:J>.~ ~iAPl;'O'NS. Bi:;!lDGE <br />leCA rEO "'ti...L DO-M-lSTREAM <br />OF NARRO'N$. <br /> <br />Gase 1: COf'1troctlo" wi Overconk Flow. <br /> <br />Cos" 2.: COf'1~roc~::'J,'" ,,/ "\0 Qver-bcnk flow. <br /> <br />/ <br /> <br /> <br />~ j v < <br /> <br />'II, <br /> <br />l.4AIN <br />CHANNEL <br /> <br />/ <br /> <br />REUEF BRIDGE ON <br />FlO JO PLANE <br /> <br />RELIEf BRIDGE O\IER <br />ACTlVE STREAM <br /> <br />8ej----in-----\J:=i,/ <br /> <br />CASE: J <br /> <br />Ot - '< + QO~8""'K n..ow <br />CASE ... <br /> <br />Co:!e :5 end 4: Relief Bridge. <br /> <br />Figure 4.1 <br /> <br />The Four Main Cases of Contraction Scour <br /> <br />36 <br />