Numerical Modeling of Stage-Discharge Relationships in Urban Streams

Quantitative relationships for converting recorded water levels to discharge records in urban streams typically have high levels of uncertainty, particularly for high flows. This problem results from the inherent difficulty in making direct discharge measurements during storms in urban watersheds with flashy runoff response. This paper describes an approach using a 2 - D depth-averaged numerical model (TUFLOW) to support rating curves for stream gauges in Baltimore. Multiple forms of field-measured data are used to test and adjust the model-based curves, including surveyed water-surface profiles and high-water marks. Discrepancies between modeled curves and discharge measurements were 0.021-0.085 m(3) s(-1). The average of modeled and measured water-surface profiles matched to within 0.04-0.08 m of water depth. This method facilitates the generation of rating curves encompassing the full range of flows for which patterns of runoff response impede measurement of high flows allow simulation of complex flow behavior that may influence stage-discharge relationships. DOI: 10.1061/(ASCE)HE.1943-5584.0000459. (C) 2012 American Society of Civil Engineers.