Controlling Polluted Stormwater Runoff From Roads

Wemple, B. (2016) Controlling Polluted Stormwater Runoff From Roads. Vermont Journal of Environmental Law, 17(4), 785-810.

Transportation networks are a critical component of society’s infrastructure, providing access to move goods and people through the landscape, but with environmental impacts that affect a range of ecosystem processes, including animal migration patterns, exotic plant propagation, and the production of runoff and water quality contaminants. The linear nature of roads and their tendency to collect, concentrate, and route water and pollutants along the road corridor and roadside-ditch network result in impacts to watershed processes on a scale far greater than one might expect from the small fraction of land area they occupy. The effects of roads on water quality are linked to the ways in which roads, as impervious surfaces, influence runoff (or stormwater) production and redistribution. Within mountainous or upland settings, where unimproved, gravel or native surfaced roads are common, these runoff and water quality dynamics involve changes to the processes of rainfall infiltration, groundwater percolation, and delivery of stormwater to streams. The scientific work to document unpaved road impacts on runoff and water quality has been driven by a need to understand land management impacts and the need to mitigate these to comply with federal and state clean water regulations and other environmental regulations.

This article seeks to outline what we know about the impacts of unpaved roads on water quality in the Lake Champlain Basin and similar settings of the northeastern United States. Section I lays out the ways in which roads alter processes of stormwater production and routing, with impacts on erosion and water quality. This is followed in Section II by a general description of transportation networks in mountainous landscapes to provide context for both the local reader and for those interested in parallels to landscapes elsewhere. Section III provides a summary of empirical work in Vermont to examine the role of unpaved roads on water quality. Section IV summarizes experimental and retrospective assessments used to evaluate the effectiveness of practices to mitigate against these impacts. Section V ends with comments aimed to place the “road impact” into broader perspective, for those concerned with water quality management, and with comments on barriers to implementation of practices to address road impacts on water quality.