Management of strom water for drainage of Azimpur, BUET, and Lalbag area of Dhaka city

Abstract

In the recent years, it ha, become" common p'cture in Azirnpur, BUET and L.lbag that if there is a rainfall of moderate to severe intensity, major portion of the area goes under water. This stody focllses 0" the flooding L.used by high intensity "orm rmlOff thot inundate, these areas for ,eveml day' maLnl)' due to Jack of proper d"'-in.ge sY"em and lnefficient management Selection of ,rudy M~a " gllided by tbe availability of ,mf.ce runoff .nd ,hort durallon rainf"ll ,]". of the urban catchments, DelJneation of the catchment Was bilsed On stonn sewe," of DWAS.-'l, slt:eet map of DeC, Google Eanh Image, prL'vious study .nd field ob'~[vaDOn, Slnce th~ land Is very flat, the ca"hmen! boundary depends very little on the topog"phy, r-.1Jk~SWl\-IMrainf.1l nmoff Model i, a popular, effective ~nd useful t"ol, wltich ca~ support I'I~ntung 'nd m.nagemcnt for m,kmg effeetlve deci,ion. [n thi, stud)' Mike SWl\-ll\-lrunoff mod"le i, mod for runoff generation .nd Ext"'-n module i, used for ,imuhttion of the 'urf.ce Row. In th" study two cn[chmcnts Me delinealed for simolat'on of old and new ,torm ,ewers b)' )I.-fikeSWMM model One catchmell! is the old storm sewer of BUET and [he other is the newly constructed stOrm 'owe, which goes through flUET, D.keshwari Mondlr and patt "f Azirnpur .nd Lalb.g .ren" BUET c.tchcmnt " divided Into 17 subcatchment, to ,imulate the old >lOrm,,,,vet no",'ork. C"lib",tion and verification is po,,,ble for sub.eatchment no-6 of old storm 'ewe, n~twork for [he yo", 1996, MO"'uted runoff and rainf~tl data is found only for [hISsubcathcment for the ye.r 1996.SWMM EK!,"n block run wa, not pOSSiblefor I.ok of dam on the old stOrm ,,,,vcr. Ncw stOrm ,cw~r goe, through the part of the BUET c.tcbmmt. So, catchemm bound.ry for ncw storm ,,,,vcr is different from old storm sewer catchment 'I1,i, e.!chmen! is dMdcd into 63 sub-catchments, J.D_F Cutve i, used to gener",,, 5 minu!", In[erval ",-inf.1ld"t. Wltb" stall"'e.1 return period of 2, 3, 5 and 10 yea". Cumulative ",inf.ll of 2, 3, 5 and 10 )'0." retutn period" aceordlt\gly 31.57 mm, 91.90 mm, 105,94 Jnm and 123,53mm, vii Rainfall and 'tarm ,ewer discharge data for the 1996 mon,oon at BUET <:atchmont was collec'od from. prov,ou, study (chowdhury ct ,1., 1998). TI,e information on the drrtinagc network (,econdary and primory/trunk drain) of ,hc model area wete collec'ed from DWr\SA Old network dam" not ~va,hble and reccntly "'stallcd ,ewer 'ystem drawing" O\'~ilablefor the BUET ca'chment. It includes dwuled 'nfarm.uon .bou' <1wdllrtcnSlon and [JOttomelevation of the p'pes, location and ,ize of the manholes and ca'chp,t,. A ,Ct of ,mall, medium and large storms were ,elected from mon,oon 1996 and divided in[O two ,ub-sels of equal ,ize, one for c.Ub"tion .nd tho other for venfication. Root me~n 'quare ."or; for calib"ted storm, arc acconlJng 3 5%, 12.07% .nd Hi.10% and correlauon cocffLcients(R') arc 0 917, 0,951 and 0.913, Old ,torm 'ewer network surface flow simulation is not possiblc beeausc of Jack of ,ewer dam, Subcatchment parameters of ,he old storm 'ewer of BUET catchment is u;cd in the new storm sewer catchment, SWMM Extran Block Is used (0 tcst the capacity of <lewly cons!ru<;ledswnn 'ewer I\lthough in thc Master Pion OleA, 1992) the rainfall intensity ",th as-yen, freyuency was recammended (0 de,ign the stOrm sewer, i, " lnadegua{e to hondle the 2 YOOffre'lLLencyrainfall. l'l"nlllng, de,ign, opc"'t1on and maintenance of urban drninnge 'r'toms arc a grcat challenge to mba" aulharities i" dcvciopi"g COuntne, becnu," of unplanncd development activities. Short deSlgn retUrn pen ods ftre '"metime, "oco"'ry because of the prohibltlve cost of building a drmnage system to cope with all monsoon storm,. Integrated .pproaeh i, nceded among ,he gove'"mcnt agencies [0 stormwatcr management, and public parucip.tlon based 0" ftW"rene,"of [he purpo,e and function of {hed""n'ge infra<trucrure.