City of Federal Way Panther Lake Surface Water Study?A Case Study of HSPF Modelling in Urban Detention Basins

by Andrew B. Lukas, Brown and Caldwell Consultants, Seattle, United States,
Cary M. Roe, Brown and Caldwell Consultants, Seattle, United States,

Document Type: Proceeding Paper

Part of: Water Management in the '90s: A Time for Innovation


This paper presents a case study of using Hydrologic Simulation Program-Fortran (HSPF) as a tool for sizing large urban detention facilities. The Panther Lake drainage basin is a textbook case of the effects of urbanizing a forested area. The study itself combined the elements of urban surface water runoff control, hydrologic computer modelling, detention pond sizing, and environmental impact assessment. In an earlier study, Panther Lake was determined to be a priority in ensuring the stability of downstream natural channels due to its importance with regard to flooding prevention, stream bank erosion control, and habitat protection. Originally the lake was a closed depression, totally in equilibrium with its forest setting. However, with urban development creating impervious surfaces, and the installation of man-made drainage structures that extended the tributary area, the storage of urban runoff from over 526 hectares (1300 acres) was required of the closed depression. Refinements of the tributary area, storage capacity, and outlet hydraulics of the lake were made in order to make an accurate assessment of the amount of additional storage required at the closed depression in the event of a 100 year storm. A first set of alternatives was developed from this data, from which three feasible solutions were chosen and then tested with HSPF to determine their adequacy in a 100 year event.

Subject Headings: Hydrologic models | Computer models | Urban areas | Lakes | Case studies | Water storage | Municipal water | Washington | United States

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