Baltimore Ecosystem Study Cary Institute of Ecosystem Studies

2012 BES Annual Meeting Presentation and Poster Abstracts

Geospatial analysis of topography and development patterns for comparison with hydrologic response characteristics of Gwynns Falls subwatersheds
Schmidt, Kevin
Co-Authors: Kevin Schmidt (1), Garth Lindner (2), Andrew Miller (2) : (1) - University of Delaware, (2) - University of Maryland, Baltimore County

Abstract: We used lidar topography, hydrography and urban infrastructure GIS layers to delineate watershed boundaries, augmented urban drainage network coverages and width functions (frequency distributions of flowpath distance upstream of the watershed outlet) for a series of Gwynns Falls tributaries including 6 nested stream gages in the Dead Run watershed and 4 other Gwynns Falls tributaries (Maidens Choice, Powder Mill Run, Gwynns Falls at Delight and Scotts Level). These are being compared with unit hydrographs for pulse rainfall events developed from streamflow records and HydroNEXRAD radar rainfall data. Watershed outlines were delineated based on lidar topography at 5-m grid scale with information from both the channel network and the storm drain network burned into the topographic data set. An augmented channel network was created by merging hydrography and road layers based on the assumption that roads and parking lots could be treated as equivalent to headwater tributaries. A raster representation of each of the study watersheds was generated using the delineated watershed boundaries and the augmented channel network. This raster was used to develop a set of width functions. The width functions simulate the frequency distribution of arrival times in the unit hydrograph based on an assumed ratio of hillslope:channel flow velocity. Preliminary results indicate that the inclusion of roads and parking lots in the augmented drainage network produces a realistic width function that resembles characteristic storm response patterns for these urban watersheds, and allows us to identify where the width function differs from actual watershed response.