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An analytic approach to ascertain saturation-excess versus infiltration-excess overland flow in urban and reference landscapes
Citation:
Stewart, R., A. Bhaskar, T. Parolari, D. Herrmann, J. Jian, L. Schifman, AND W. Shuster. An analytic approach to ascertain saturation-excess versus infiltration-excess overland flow in urban and reference landscapes. Hydrological Processes. John Wiley & Sons, Ltd., Indianapolis, IN, 33(26):3349-3363, (2019). https://doi.org/10.1002/hyp.13562
Impact/Purpose:
One of the major challenges in the field of hydrology is prediction of how soils will initiate overland flow, which is commonly referred to as runoff. Runoff is generated in two ways: infiltration-excess, or saturation-excess. We present an analytic approach to determine the tendency of urban soils to present with either of these processes. Actual hydraulic field data from 11 cities is used in this study to drive simulations that are forced with estimated rainfall pattern for the same cities.
Description:
Overland flow can cause deleterious environmental effects such as flooding, contaminant mobilization, and erosion. These processes pose challenges in the context of urban stormwater management, where excess water and pollutants must be appropriately handled. Designing suitable intervention strategies requires knowledge of particular mechanisms responsible for overland flow, whose initiation can be broadly divided between infiltration-excess (where the rainfall rate exceeds infiltration capacity) or saturation-excess (where the soil profile storage becomes depleted) processes. In this study, we propose a generalized one-dimensional model that distinguishes between infiltration-excess and saturation-excess overland flow. We then use the model to estimate overland flow generation from pervious areas within urban environments, specifically by comparing measured urban with pre-development reference soil properties. Eleven U.S. cities, representing a range of soils and climatic conditions, were evaluated using 2-year return interval storms (a high-intensity 1-hour storm and a lower-intensity 24-hour storm). The analysis showed that the propensity for infiltration-excess versus saturation-excess overland flow could be identified using two non-dimensional numbers representing the ratios of: 1) precipitation rate to depth-weighted hydraulic conductivity, and 2) depth of restrictive layer to soil capillary potential. Individual cities showed varying hydrological responses, but in general reference soil profiles generated more infiltration-excess overland flow during high-intensity events whereas pervious urban soil profiles generated more surface-excess overland flow during lower-intensity storms. These results can assist cities in identifying the type and extent of intervention needed as part of their water management strategies, and can apply to other systems in which overland flow generation processes have relevance.
URLs/Downloads:
DOI: An analytic approach to ascertain saturation-excess versus infiltration-excess overland flow in urban and reference landscapes
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