An analytical approach to ascertain saturation‐excess versus infiltration‐excess overland flow in urban and reference landscapes. Issue 26 (28th August 2019)

• Record Type: Journal Article
• Authors: Stewart, Ryan D.; Bhaskar, Aditi S.; Parolari, Anthony J.; Herrmann, Dustin L.; Jian, Jinshi; Schifman, Laura A.; Shuster, William D.
• Is Part Of: Hydrological processes. Volume 33:Issue 26(2019)
• Page Start: 3349
• Page End: 3363
• Publication Date: 2019-08-28
• Subjects: infiltrations -- storm water run‐off -- urban hydrology -- urban soil; Hydrology -- Periodicals; Hydrology -- Research -- Periodicals; Hydrologic models -- Periodicals; Hydrological forecasting -- Periodicals; 631.432
• DOI: 10.1002/hyp.13562
• Languages: English
• ISSNs: 0885-6087

Abstract

Abstract: Uncontrolled overland flow drives flooding, erosion, and contaminant transport, with the severity of these outcomes often amplified in urban areas. In pervious media such as urban soils, overland flow is initiated via either infiltration‐excess (where precipitation rate exceeds infiltration capacity) or saturation‐excess (when precipitation volume exceeds soil profile storage) mechanisms. These processes call for different management strategies, making it important for municipalities to discern between them. In this study, we derived a generalized one‐dimensional model that distinguishes between infiltration‐excess overland flow (IEOF) and saturation‐excess overland flow (SEOF) using Green–Ampt infiltration concepts. Next, we applied this model to estimate overland flow generation from pervious areas in 11 U.S. cities. We used rainfall forcing that represented low‐ and high‐intensity events and compared responses among measured urban versus predevelopment reference soil hydraulic properties. The derivation showed that the propensity for IEOF versus SEOF is related to the equivalence between two nondimensional ratios: (a) precipitation rate to depth‐weighted hydraulic conductivity and (b) depth of soil profile restrictive layer to soil capillary potential. Across all cities, reference soil profiles were associated with greater IEOF for the high‐intensity set of storms, and urbanized soil profiles tended towards production of SEOF during the lower intensity set of storms. Urban soils produced more cumulative overland flow as a fraction of cumulative precipitation than did reference soils, particularly under conditions associated with SEOF. These results will assist cities in identifying the type and extent of interventions needed to manage storm water produced from pervious areas. Abstract : Municipalities may alter their storm water management focus depending on the most relevant processes (left); the analytical framework developed in this study can be used with measured soil properties to estimate the propensity of urban versus predeveloped reference soil profiles towards saturation‐excess overland flow (SEOF) or infiltration‐excess overland flow (IEOF), with 11 cities in the United States analysed (right).