Itisacommonpracticetouseahydrologicalcontinuityequationasthegoverningequationindetentionponddesign.Althoughthedetentionvolumecanbeevaluatedusinganumericalmethodandcomputerprogram,theyarenotavailableforengineerstousebecauseofthedifficultyinvolvedinthenumericalevaluationorthecomputerprogrammaynotbereadyforengineers.Thisstudyintendstoprovideaformulaforcalculatingthevolumeofadetentionpond.Anonlinearcontinuityequationfordetentionponddesignisobtainedbyapplyingatriangular/trapezoidalinflowhydrographandspillwayororificefortheoutflowdevice.Thisperturbationmethodisemployedtoresolvetheequation.Afterdiscussingtheomissionandcurvefittingmethods,aformulafordetentionponddesignisproposed.Severalexamplesaredisplayedandahighagreementwiththenumericalresultisobtained.
