Detailed hydrologic investigations were completed for a stream system that could affect a large retail location in New Jersey. Site-specific evaluation of the rainfall-runoff process in the basin and how those would affect the location given various levels of rainfall intensity in time and space were evaluated. This included detailed quantification of the stream characteristics including land cover, infrastructure (road, bridges, LIDAR surface, etc). These were modeled within the HEC HMS and 2D modeling environments and combined with AWA’s SPAS outputs to produce a site-specific runoff evaluation.
The result demonstrated that the location was at more risk to a 100-year level rainfall event over 6- and 24-hour durations than previously thought from standard NOAA Atlas 14 and FEMA information. This provided explicit outputs on the duration of flooding, the flood water surface elevations, the durations of various evaluations, and the speed of the water movement against and around the location of interest. This provided the information and data needed to make more accurate risk assessments, develop flood prevention plans, and properly insure the location.