Assessing the Accuracy of HydroCAD for Pre-Development Runoff in Wooded Coastal Watersheds

Details

• Journal Title:
  Journal of Ecological Engineering Design
• Personal Author:
  Ownby-Connolly, Briar ; Connolly, Matthew Huth ; Chambers, Randy ; Knapp, Landon ; Strosnider, William
• NOAA Program & Office:
  Sea Grant
• Sea Grant Program:
  SCSGC (South Carolina Sea Grant)
• Description:
  Urbanization increases stormwater runoff that, without proper management, leads to eroded channels and impaired downstream water quality and habitats. To simplify pre- and post-development calculations of stormwater runoff, Technical Release 55 (TR-55) was established by the United States Department of Agriculture in 1986 and adopted for use by engineering firms nationwide. The commonly applied HydroCAD stormwater modeling software utilizes TR-55, which is meant to help engineers ameliorate pressures from increased runoff due to urbanization, guiding Best Management Practice (BMP) design. We evaluated this conventional modeling method using 2 field sites to test limitations of TR-55 within HydroCAD. In-situ stream flow velocities, rainfall data, soil samples, and topographic surveys were used to compare model results with site data and observations. We identified hydrologic soil groups as the most influential parameter, where misclassified soil groups, specifically for undeveloped wooded areas, led to current standard practices that underestimate infiltration. As a result, the HydroCAD model overestimated pre-development peak discharge rates (Qp) by approximately 710% and 240% at our 2 field sites. Due diligence in corroborating soil mapping was crucial, as uncorrected model outcomes can cause deleterious downstream effects via undersized BMPs. The large error rate observed indicates that the standard assumptions of TR-55 within HydroCAD should be revisited not only in undeveloped wooded areas, but in other prevalent land cover types.
• Source:
  Journal of Ecological Engineering Design, 4(1)
• DOI:
  https://doi.org/10.70793/jeed.27
• ISSN:
  2997-3112
• Format:
  pdf
• Publisher:
  University of Vermont Press
• Document Type:
  Journal Article
• License:
  https://creativecommons.org/licenses/by-nc-nd/4.0/
• Rights Information:
  CC BY-NC-ND
• Compliance:
  Library
• Download URL:
  https://repository.library.noaa.gov/view/noaa/75605/noaa_75605_DS1.pdf
• File Type:
  [PDF - 1.69 MB]
• Collection(s):
  Sea Grant Publications
• Main Document Checksum:
  urn:sha-512:814393768be033e32590631981e1cfd4fce8a8839bfc8541fdf17e73526a21a8f2ee6c085ae7ad2370acaf1cfac0632e559130089d38f1814854b0c1abedfc67