USE OF PEAK FLOW CURVES IN HYDRAULIC MODELING AND POST-REHABILITATION ANALYSIS

摘要

The Jefferson County, Alabama Environmental Services Department is currentlyrnimplementing a program to address wet weather overflows in its wastewater collectionrnsystems. Two important components of this program are collection systemrnrehabilitation and capacity improvements. Through the use of an extensive network ofrnflow monitors and rain gauges in each collection system, the extent of neededrncapacity improvements as well as the impact of rehabilitation can be assessed.rnA relationship between rainfall amount and peak flow rate can be established usingrndata from these flow monitors and rain gauges. Several criteria should be used inrnselecting rain events used in the development of this relationship. Rain events shouldrnbe: (1) preceded by a period of dry weather, (2) homogeneous in rainfall amount overrnthe basin, (3) below a point that causes collection system surcharging, and (4) ofrnshort duration.rnThe use of this rainfall ?peak flow relationship over actual flow data allows a morernaccurate projection of the capacity requirements of design storms. Actual flow datarnfrom storms large enough to cause surcharging results in an understatement ofrnpotential peak flows.rnUse of this relationship can also determine the impact of rehabilitation on peak flowrnrates. However, this method should not be used exclusively as it does not assess thernimpact of rehabilitation on high groundwater infiltration (HGWI). For systems withrnextensive and frequent surcharged conditions, this analysis also proves the need forrnboth capacity improvements and rehabilitation.