Evaluation of the Effectiveness of Green Infrastructure for Stormwater Management Under Current and Future Climates in Buffalo, New York.

Abstract:

Efficient management of stormwater is imperative to future performance of city infrastructure. Impervious surfaces in urban areas inhibit recharge and infiltration while intensifying runoff. Rust belt cities such as Buffalo, New York have higher percentages of vacant impervious surfaces and aging grey infrastructure. As a result, mitigation of projected increase in rainfall quantity in urban Buffalo is essential to maintain drinking water standards and limit probability of combined sewer overflow (CSO). Rain gardens are one form of green infrastructure (GI) which have already been implemented around the west side of Buffalo. Without GI, excess rainfall discharges to the older combined sewer systems whereas with GI, water infiltrates to the water table as groundwater recharge, or evapotranspires. Collaborators at the Buffalo sewer authority and PUSH Buffalo have installed the rain gardens however, there have been limited studies quantifying their efficiency.

Using field observations and numerical models, one can gain insight to the usefulness and practicality of GI installation. Field observations were incorporated within five representative models to calculate rain garden efficiency and forecast future climate scenarios based on selected GI on the west side of Buffalo. Performance of five rain gardens with different constructions were evaluated using HYDRUS 1D, a variably saturated flow modeling system. Soil moisture, matric potential, soil characterization, and root distribution data were collected at existing GI to calibrate and validate the models. Seasonal precipitation forecasts via downscaled climate models were coupled with each model using data from the North American Regional Climate Change Assessment Program (NARCCAP). The NARCCAP data is included to evaluate future climates from 2041-2070. The goal of the research is to give water managers across the Great Lakes predictive power to prepare for future increases in runoff and CSO, and to evaluate current efficacy of rain gardens. Rainfall is projected to increase over the next 30 years across the Great Lakes region, which emphasizes the importance of infiltration and evapotranspiration of stormwater.