Repository logo
 

Morphologic characterization of urban watersheds and its use in quantifying hydrologic response

Date

2009

Authors

Gironás, Jorge, author
Roesner, Larry A., advisor
Niemann, Jeffrey D., advisor
Ramírez, Jorge A., committee member
Stednick, John D., committee member

Journal Title

Journal ISSN

Volume Title

Abstract

Current methods for hydrologic characterization of urban watersheds and analysis of the impacts of urbanization are primarily based on the description of imperviousness and how changes in this characteristic affect storage, infiltration, and runoff generation. The morphology of urban watersheds and the effects of urbanization on the structure of the drainage system have been much less studied. The overarching objectives of this study are to develop methodologies to characterize the morphology of urban drainage systems including the hillslopes, streets, pipes, and channels and to use this characterization to model the hydrologic response of the watershed. These objectives are accomplished through: (a) an exploration of potential applications of morphologic theories in the characterization of urban watersheds and the impacts of urbanization; (b) the development and testing of a methodology to generate urban terrains (i.e. a raster representation of the topography) in which the effects of conduits typically observed in urban areas are represented; and (c) the development and testing of a new rainfall-runoff model called the U-McIUH (Urban Morpho-climatic Instantaneous Unit Hydrograph). The model is based on the morpho-climatic instantaneous unit hydrograph theory, in which the hydrologic response is identified from the spatial structure of the watershed and the properties of the storm event. The morphologic approach adopted reveals significant impacts of urbanization on the internal structure of natural watersheds at a wide range of scales. This finding is relevant when building stormwater models intended to simulate and compare the pre- and post-development catchment response. The morphologic impacts should be incorporated into stormwater models through the redefinition of model parameters that characterize both the channelized and unchannelized portions of the catchment when the urbanized scenario is simulated. This research also shows the importance of incorporating artificial conduits into urban terrain for hydrologic modeling. A new method to incorporate the artificial conduits into the DEM based on the real elevation of these conduits proved to be superior to other previously available methods because it better represents the flow directions and flow paths. Finally, the new rainfall-runoff model developed in this study fills an existing gap in the field of distributed stormwater modeling. It provides a more thorough treatment of the flows in minor conduits and unchannelized portions of the watershed, which enhances the simulations of runoff accumulation that are traditionally used in conceptual models. The model is parsimonious and uses a simplification of kinematic wave routing that considers the dependence of the unit hydrograph on rainfall intensity and the effect of upstream contribution on the travel times without explicitly solving the flow equation at each cell for each time step. This simplification reduces the complexity of the model computations while still producing reasonable model performance.

Description

Covers not scanned.
Print version deaccessioned 2022.

Rights Access

Subject

Urban runoff
Urban hydrology
Urban watersheds

Citation

Associated Publications