Practical Application of Hydraulic Tools in Urban Stormwater Design

Abstract

The purpose of this study was to identify appropriate hydraulic modeling technologies to aid in the design of urban stormwater systems for small and medium sized communities. The unnamed channel used in this research is approximately 2,500-feet long and located in the Rolling Acres Subdivision in Enid, Oklahoma. The channel and eight adjacent houses were surveyed to establish elevations. Flowrates were established using HEC-HMS model from a previous study of this basin. Bentley's FlowMaster software was used to determine the channel geometry while Bentley's CulvertMaster software was used to determine the culvert size at three roadway crossings. Both FlowMaster and CulvertMaster were found to be very easy to use and provided acceptable results. Because the subdivision was developed outside prior city limits, this channel and adjacent houses were not constructed according to local stormwater regulations or with future, upstream development considered. These nearby, low lying houses as well as existing utilities provided difficult constraints that could not be modified without significant costs. Therefore, the FlowMaster model required both wide channels and concrete-lined channels to prevent house flooding. The CulvertMaster model was able to provide culvert sizes that, while smaller than ideal, resulted in headwaters that would not flood adjacent houses.