The effects of green infrastructure on exceedance of critical shear stress in Blunn Creek watershed

Sa’D Shannak

doi:10.1007/s13201-017-0606-5

Abstract

Green infrastructure (GI) has attracted city planners and watershed management professional as a new approach to control urban stormwater runoff. Several regulatory enforcements of GI implementation created an urgent need for quantitative information on GI practice effectiveness, namely for sediment and stream erosion. This study aims at investigating the capability and performance of GI in reducing stream bank erosion in the Blackland Prairie ecosystem. To achieve the goal of this study, we developed a methodology to represent two types of GI (bioretention and permeable pavement) into the Soil Water Assessment Tool, we also evaluated the shear stress and excess shear stress for stream flows in conjunction with different levels of adoption of GI, and estimated potential stream bank erosion for different median soil particle sizes using real and design storms. The results provided various configurations of GI schemes in reducing the negative impact of urban stormwater runoff on stream banks. Results showed that combining permeable pavement and bioretention resulted in the greatest reduction in runoff volumes, peak flows, and excess shear stress under both real and design storms. Bioretention as a stand-alone resulted in the second greatest reduction, while the installation of detention pond only had the least reduction percentages. Lastly, results showed that the soil particle with median diameter equals to 64 mm (small cobbles) had the least excess shear stress across all design storms, while 0.5 mm (medium sand) soil particle size had the largest magnitude of excess shear stress. The current study provides several insights into a watershed scale for GI planning and watershed management to effectively reduce the negative impact of urban stormwater runoff and control streambank erosion.

Highlights

Urbanization has caused massive increases in impervious coverages and as a result the amount of stormwater runoff, which in turn can have harmful effects on urban and suburban streams
Data used in the modeling were the following: 15-min rainfall data downloaded from the Flood Early Warning System and Water Quality Monitoring sections at the City of Austin (COA) station, daily temperature data from the Austin and Austin– Bergstrom National Oceanic and Atmospheric Administration weather stations were used, weather zone from (WGEN_US_COOP_1960_2010), 3 m integer Digital Elevation Model (DEM) developed by City of Austin based on 2003 LIDAR data and SSURGO soil data Natural Resources Conservation Services (NRCS)
The sub-hourly 15-min time step Soil and water assessment tool (SWAT) model was developed and integrated with different levels of Green infrastructure (GI) to study their impact on the exceedance of critical shear stress and potential stream bank erosion

Summary

Introduction

Urbanization has caused massive increases in impervious coverages and as a result the amount of stormwater runoff, which in turn can have harmful effects on urban and suburban streams. Konrad et al (2005) studied the impact of urban development on stream flow and streambed stability They examined 16 streams in the Puget Lowland, WA, USA, using three streamflow metrics that integrate storm-scale effects of urban development over annual to decadal timescales. Cheveney and Buchberger 2013 conducted a study to evaluate the impact of GI in mimicking pre-development scenario in the Mill Creek Watershed, which is located in southwestern Ohio. They applied a water balance analysis using the modeling software, Aquacycle. They noticed that two values were significantly changed, the total volume of water entering and leaving the watershed increased by 28% and the annual

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