by Christine Colley, ASLA, RLA, and Lucy Joyce, ASLA
Does your state Department of Transportation (DOT) have standards for green infrastructure (GI)? A recent study from the National Cooperative Highway Research Program (NCHRP) investigated how transportation agencies are applying the principles and practices of GI. The study—Leading Landscape Design Practices for Cost-Effective Roadside Water Management—was requested by the American Association of State Highway Transportation Officials (AASHTO) and prepared by a team of experts that included Federal Highway Administration (FHWA) and DOT staff from across the country (California, Minnesota, Washington, Maine, Louisiana, and Nevada). The team scanned existing state DOT GI regulations, targeted regional, city, and DOTs with robust GI programs, and conducted a deep dive into GI standards and specifications. The intent was to suss out successful and unsuccessful practices with an eye toward developing guidelines for state and other public agencies to use when creating GI programs.
The study defined green infrastructure as roadside stormwater management, low impact development (LID), and hydromodification or watershed actions that conserve water, buffer climate change impacts, improve water quality, water supply, and public health, and restores and protects rivers, creeks, and streams as a component of transportation development projects and operations. Despite substantial documentation on GI design, buy-in from all levels of government (federal, state, and local), ample research, and a plethora of knowledgeable consultants, the team found that state DOTs do not consistently employ GI techniques and often only use them when required by regulatory agencies. The study was developed to help inform public agencies on the components of successful GI programs.
