Leading Landscape Design Practices for Cost-Effective Roadside Water Management – A Review

by Christine Colley, ASLA, RLA, and Lucy Joyce, ASLA

cover images from the Leading Landscape Design Practices For Cost-Effective Roadside Water Management / images: Nevada Department of Transportation, New York City Department of Environmental Protection report
Leading Landscape Design Practices For Cost-Effective Roadside Water Management / images: Nevada Department of Transportation, New York City Department of Environmental Protection

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 Managementwas 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.

In November 2017, the scan team invited host agencies to participate in a Peer-to-Peer workshop. The scan team developed a list of “Amplifying Questions” to provide a comprehensive set of responses regarding each agency’s approach and practices for GI. The amplifying questions fell into six categories, including agency information, GI techniques, performance measures, maintenance, miscellaneous questions, and city/MPO-specific topics. These questions were reviewed during the workshop along with a review of watershed management practices, and activities from seven state DOTs (Arizona, Maryland, Michigan, Pennsylvania, Oregon, Nevada, and Washington) and five cities, counties, or regional agencies.

At the end of the workshop the scan team identified eight critical categories that determined the success of a GI program. These “Categories of Importance” are:

  • A standardized, national definition of green infrastructure. The study listed four differing definitions of green infrastructure from the EPA, FHWA, American Rivers, and Wikipedia. The team concluded that having a clear definition for GI would clarify grant funding, federal eligibility, design approaches, and help to create categories for GI projects.
  • Maintenance and the development of maintenance teams dedicated to green infrastructure. Maintenance was identified as a critical element in achieving public and maintenance staff buy-in for GI. The team recommended that maintenance be considered in a project’s early planning and design phases. Projects with significant GI infrastructure should include a well thought out maintenance plan that includes training for maintenance staff, adequate maintenance budgets and maintenance tracking systems.
  • Watershed Approach versus Project Site Approach. Using a watershed approach provides state DOTs with the flexibility to implement GI at the proper location(s) and scales. Oftentimes rights-of-way (ROW) are too narrow to accommodate GI practices within the limits of an individual project. Using a watershed approach for permanent stormwater management practices increases the chances of a GI program becoming accessible and attainable. The team also recommends FHWA funding for maintenance activities.
  • Information Development and Sharing. Creating a central repository or clearinghouse of information on Green Infrastructure practices would help agencies gather the information needed to start GI programs or evaluate options.
  • Public Outreach. Public support for GI practices was identified as critical to a successful GI program. Vegetation establishment time frames, aesthetics, and a project’s intent are a few of the topics that the public should be aware of before a GI practice is installed. Agencies are advised to clarify and set realistic expectations using education and outreach via a public information officer or communications expert. Advocacy outreach should include local, regional and national legislators to ensure funding and support.
  • Asset Management. Green infrastructure practices should be included in a state DOT agency’s Asset Management program. Tracking assets such as GI facilities enable DOT staff to accurately assess the impact of the practice on water quality and other performance measures as well as develop reports to regulatory agencies. Asset management systems are also used to track maintenance and budgeting for maintenance activities.
  • Design. Design standardization for GI practices—especially those required by federal and state regulations—was another recommendation. Using an interdisciplinary design team that includes landscape architects provides extra assurance that the practice and standards are successful. FHWA, AASHTO, and state agencies should take the lead on developing research that supports the use of GI measures. Incorporating GI practices into AASHTO’s “Green Book” (A Policy on the Geometric Design of Highways and Streets) was also noted as critical for acceptance within state DOTs.
  • Construction Inspection of Temporary and Permanent BMPs. To ensure that GI practices are functioning as intended, meeting regulatory requirements and are aesthetically pleasing, the team recommended that agencies provide construction staff with proper training. This includes hiring staff that are familiar with plant ecology and site re-vegetation techniques. Further, the team noted that discrepancies between the time needed to properly establish vegetation and time given to close out a construction project results in rights-of-way that are not completely or satisfactorily re-vegetated. Contractor’s lack of compliance with specifications and field personnel that don’t adequately understand plant material are other obstacles. Requiring site management plans that include stormwater, construction and post-project vegetation and erosion control management are some of the measures recommended by the team.

The report is studded with examples that support each of the eight critical categories. These examples were gleaned from the seven state and five local (cities, counties, and MPOs) agencies reviewed during the Peer-to-Peer exchange. The examples include graphics, maintenance protocols, inspection checklists, photos, signs, report excerpts, and construction documentation (plans, details, specifications, etc.). The report’s final section outlines an implementation strategy to ensure that the contents of the report are widely distributed, read, and utilized. Appendices include contact information for the scan team and participating agencies. Appendix C outlines the seven “Amplifying Questions” and Appendix D contains each involved agency’s response to the questions.

The team concluded that a successful GI program uses a holistic approach—incorporating planning at the watershed level, asset management, and maintenance. The long-term success for GI programs is achieved when GI is considered as part of an entire system rather than segmented on a project-by-project basis.

Christine Colley, ASLA, RLA, is Senior Landscape Architect at the New York State Department of Transportation and a Transportation Professional Practice Network (PPN) Officer.

Lucy Joyce ASLA, is co-chair of the Transportation Professional Practice Network (PPN) and previously served as Landscape Architect Supervisor, Nevada Department of Transportation (retired 2016). As the Landscape Architect Supervisor Supervisor, she oversaw the creation and implementation of the Nevada Department of Transportation’s award-winning Landscape and Aesthetics Program. Lucy served as Subject Matter Expert (SME) on the scan team for Domestic Scan 16-02, Leading Landscape Design Practices for Cost-Effective Roadside Water Management.

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