HydroCAD® Stormwater Modeling - Since 1986

Modeling Residential Site Development with HydroCAD

HydroCAD case study submitted by McCrone, Inc.

Project Overview

Noble's Pond ClubhouseNoble’s Pond is a residential community being developed by Regal Builders in Kent County, Delaware. It is a medium density planned unit development consisting of both single family and duplex dwellings. The project includes a clubhouse and pool surrounded by 850 lots on approximately 293 acres. McCrone, Inc. was retained to provide infrastructure design and guidance through the Kent County permitting process for the multi-phase project. One of the key aspects of the permitting process was stormwater management. The site drains to a high-quality watercourse and the downstream effects of stormwater runoff were a major concern to the community.

Pre-Development Hydrology

Existing Farm PondThe site is primarily low-relief, poorly drained farmland including some wooded wetlands and several ponds. The parcel is divided by streams and contains many sumps. The stormwater management study point was identified at the intersection of Fork Branch (the parcel’s boundary to the south) and one of its unnamed tributaries, which runs through the parcel. Although McCrone, Inc. was not required to study Fork Branch itself, they were required to assess and manage water quality and quantity management at the study point. After meeting with Kent Conservation District (KCD), a pre-development drainage area was modeled in HydroCAD and the results were submitted. Using HydroCAD, McCrone, Inc. modeled the farm fields, wooded areas, ditches and sumps. HydroCAD’s modeling flexibility allowed McCrone, Inc. to effectively and efficiently manage and model numerous subcatchments, as well as the complex, low-relief tailwater conditions present on the site.

Post-Development Hydrology

Part of the HydroCAD model, superimposed on the site planOnce the pre-development model was approved, a post-development model was created, utilizing large stormwater facilities to provide quantity management. During the design process, the Regional Planning Commission (RPC) requested utilization of Green Technology Best Management Practices. McCrone, Inc. identified locations where Green Technology BMP’s could be implemented while minimizing impact to the existing layout. McCrone’s engineering team then modeled the BMP’s and micro-practices with HydroCAD to achieve qualitative stormwater management goals. McCrone engineers were able to quickly model the BMP's, such as bioretention areas, bio-swales and micro-bioretention areas, utilizing the different node types available in HydroCAD. After developing working models for each BMP, the models were easily integrated into the previous quantitative model and after minor adjustments, McCrone Inc. had a working model that demonstrated both quantitative and qualitative compliance. Using HydroCAD allowed McCrone engineers to make this major design change quickly and in a cost-effective manner. This model and preliminary stormwater management report was delivered to Kent County in October 2011.

HydroCAD Routing Diagram

December 2, 2011


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