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Effects of urbanization and stormwater control measures on streamflows in the vicinity of Clarksburg, Maryland, USA
Citation:
Rhea, L., T. Jarnagin, D. Hogan, J. Loperfido, AND W. Shuster. Effects of urbanization and stormwater control measures on streamflows in the vicinity of Clarksburg, Maryland, USA. Hydrological Processes. John Wiley & Sons, Ltd., Indianapolis, IN, 29:4413-4426, (2015).
Impact/Purpose:
Accurate prediction of the response of urban stream discharges to management and changing precipitation patterns remains an active research area. We characterized the influence of urbanization and storm water control measures on the relationship between stream discharge and precipitation over a six year period for five catchments near Clarksburg, Montgomery County, Maryland USA. A transfer-function based unit-hydrograph model was employed to develop temporally invariant estimates of precipitation apportionment to stream flow for different time lags. From these lagged relationships, we quantified the correction to the precipitation time-series that was necessary to achieve a perfect hydrograph-mediated relationship between precipitation and discharge through time. Positive corrections appeared to include precipitation events not captured by our rain gages, so only negative corrections were analyzed for potential causal relationships. Nuisance variables including basin-specific intercepts, slopes, and diurnal and seasonal periodicity dominated the relationships, but agriculture, natural lands use, wet areas, and Phase 2b storm water control measures (a.k.a. best management practices, or BMPs) were also statistically significant predictors of the apportionment of precipitation to stream discharge.
Description:
Understanding the efficacy of revised watershed management methods is important to mitigating the impacts of urbanization on streamflow. We evaluated the influence of land use change, primarily as urbanization, and stormwater control measures on the relationship between precipitation and stream discharge over an 8-year period for five catchments near Clarksburg, Montgomery County, Maryland, USA. A unit-hydrograph model based on a temporal transfer function was employed to account for and standardize temporal variation in rainfall pattern, and properly apportion rainfall to streamflow at different time lags. From these lagged relationships, we quantified a correction to the precipitation time series to achieve a hydrograph that showed good agreement between precipitation and discharge records. Positive corrections appeared to include precipitation events that were of limited areal extent and therefore not captured by our rain gages. Negative corrections were analysed for potential causal relationships. We used mixed-model statistical techniques to isolate different sources of variance as drivers that mediate the rainfall–runoff dynamic before and after management. Seasonal periodicity mediated rainfall–runoff relationships, and land uses (i.e. agriculture, natural lands, wetlands and stormwater control measures) were statistically significant predictors of precipitation apportionment to stream discharge. Our approach is one way to evaluate actual effectiveness of management efforts in the face of complicating circumstances and could be paired with cost data to understand economic efficiency or life cycle aspects of watershed management. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.
