Anthropogenic controls from urban growth on flow regimes

• A stochastic model of streamflow is applied to urban basins under conditions of urban growth.
• The model is used to determine flow duration curves and different indicators of hydrologic alteration.
• Flow duration curves show consistent changes with urban growth.
• Hydrologic indicators highlight the dependence of streamflow dynamics on urban growth.

Streamflow can be drastically perturbed in urban basins with important implications for stream, floodplain, and riparian ecosystems. Normally, the dynamic influence of urbanization on streamflow is studied via space-for-time substitution. Here we explicitly consider urban growth when determining the flow regime of 14 urban basins. To synthetically represent the flow regime, we employ flow duration curves (FDCs) determined using a stochastic model. The model permits derivation of FDCs that are dependent on few parameters representing climatic, land use, conventional stormwater management, and geomorphological conditions in an urban basin. We use the model, under conditions of urban growth, to assess the influence of urbanization on key model parameters and to determine different indicators of hydrologic alteration. Overall, results indicate consistent changes in the temporal evolution of the perturbed flow regimes, which in this case can largely be explained by the progressive redistribution with urban growth of water from slow subsurface runoff and evapotranspiration to fast urban runoff.