The hydromorphology of an urbanizing watershed using multivariate elasticity

Abstract

A wide range of environmental damages have been linked to the urbanization of watersheds. While much is known about the impacts of urbanization on floods, there remains considerable uncertainty regarding the impact on average and low flows. We introduce a generalized multivariate approach for exploring hydromorphological problems that involves estimation of the multivariate sensitivity (or elasticity) of streamflow to simultaneous changes in climate, land use, and water use. Key advantages of this multivariate sensitivity method are that it does not require model assumptions in the vicinity of the mean, yet it provides confidence intervals and hypothesis tests for the resulting elasticities. A case study highlights the influence of urbanization on the complete range of streamflow. Surprisingly, low streamflows are found to have large positive sensitivity to changes in land use, which departs from the results of several previous studies. Overall, the study demonstrates that changes in climate, land use, and water use must be considered simultaneously to fully understand the hydromorphology of a watershed.