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of Dodel p.rabaterE 1f t-hj,s is ileeD€al deslrable. Itre object of lesolttng to a noo-llnea! Dod€I ts t'o avold th€ AeDenalenceof routlng par.neters on atotrr characte!1st1c6. It t ar fultha! talt Utat the rlodols ll.ght ftt l.rqcr gvant! bettcr than sealle! evgnts, because the depr€salon EtolaEg patt of th! sodlal $oulal have ).€ss of a contlol on Ule reauLt. ffre foff&fng analyslE ras perforoed fo! the uuakingu! noalal on1y, on the gtound,s ti;t a broadly s1n1lar:.€ault coulal be obtalned fo! any of the o€re! ooaiols. Fo! each cttchbent, a bean value of optln16ed Muaklngun C was obtalned, then, fo! each ovent, the variation - about thiE nean sas obtained bv, VARIATIoN = " "llgAro 'loett lhrrs, a valu€ of thls varlatlon a.bout the catchDent Dean was obtalned for each of tll€ 146 events ln the above data set. fhese were plott€d .galnst !a1nfal1 voluDe (dj,ffer€nt 3!4obols for oach catchrnent), ag 3hom 1n Flgnrre 26. Ihls !1gu!€ does deEonslrate that the variatLonB seeD to be decleaElng with incleralng Jiainfall. \roluae, although thele are Darny lore polnts aGsoclated r{lth the soallet events. v D' z,e -n '-- ,b C' r ct t 3 mct 3 =; t t VRRIFTI9NIN OPT.KVRLUE .00 . -0.t0 .10. 0 0,10 + FIGURE 26 +f rrtx x r r --t .)rFl I D.'+ FT'IF trt t t a tf{ o -ra !- 'l oil o { >r rdo o < Il _
T I I T t I T T T T T T I T I I I I I coNclusIoNs Data fron thle€ Eoulces (Netherlanda, Slteden and Ul() have been collated lnto a data base, consistlng of a total of 188 rainfalL-lun_ off eventg on 16 urban subcatchnents. A nunber of loss rnodels anal surface routlng noalels were investigated uslng lhose data' and a nuDber of opti-nlsatLolt schenes and objective functLons were examined. Ttle tradltlonal leas! squareE obJectlve function (OFl) leaves sonething to be desired aE far ag slngl€ event sinulatlon i3 concerned, but no better one could be found in the short tine avallable. rt nas decided that the nost aPProPrlate optimlsatlon scheme for a given catchnent was to alerlve optlttun bodel paralneter (s) fot each event atd then to deflne the overell optlnun as lhe arithnettc nean of the event values' Although bettei. results could sc'metlrn€s be obtaineil using a global opCirour, the advantage of the adopted schene ls that it glves nore lnfornation concerning the varlabtllty of best paranetel value(s) from event to event. A relatlonship was developed which related the deplession storage to caCchnent characterlstics. Thls legression lelationshlp could be used for estlnation on unqauqed catchments. Loss nodels were Lnvestigated first. It was considered that of the elgh! loss subnodels available, three represented the range of Dodels, and these {phl-tndex, constant proportional, loss, variable proportional Ioss) wele lnvestigated in greater detait. It was found that the phi-index nodel was slgnificantly lnferj.or to the latter tvro (at the 5c Level), but that no slgnlfj-cant dlfference couLd be obselved bet\reen these trg. The constant ptoportional loss nodel lras adopted due to lts lelatlve slrnpl-iclty and lts popularity ln the relevalt literatule. TT RLE 25 Surrmary of resu lts uodel I. LINEAR RESERVOTR 2. NONLINEAR RESERVOIRN=.67 3.NLR WITS TIIIIE LAG 4.NASH CASCADE 5 . MUSKINCUIi! 6 . TI!48 OF ENaRY Fixed N=.67 (nlnute) (hours) e = .IO Regiesslon Equati.on 1.43 sLoPE-'4oLENGTH'22 . -"LENGTH . --- .I?2 SLOPE K = . r49 sr,opE-'4lLENGTH'o89 N = 1. 19 sr,oPE-' 34LENGTH' 15 C = .o75 slopn -' 3 oi,ENcTH ' 18 tE = 74.4 sr,ope-' 27r-eNGT!l' 13 Correlation Coef,ficLent .77 .70 .75 .7r .68 .64 ';'7
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