Needle in a Haystack? Found it ! How to Locate Green Stormwater Infrastructure in Dense Urban Environments

Mini Abstract Finding locations to implement green infrastructure in dense urban environments, to meet the many necessary and cumulative siting criteria is generally a headache, time-consuming and prone to errors. This presentation will describe our automated/innovative GIS based tool which identifies locations that meet all stated criteria for GIS implementation. As an added bonus, the tool also estimates the pollutant removal ability of selected GI locations. ABSTRACT Introduction — Green Stormwater Infrastructure (GSI) makes use of plants, soils, permeable materials, and other landscaping features to capture and filter stormwater and recharge groundwater. It brings community benefits that range from flood control, water quality improvements to a reduction in urban heat island effect. GSI differs from gray infrastructure in that it typically manages/treats stormwater where it falls — gray infrastructure typically conveys the stormwater to another location. Challenge - If your municipality is a dense urban environment, or has densely packed sectors, you know by now that identifying suitable locations for GSI installations is a major challenge. The distributed nature of GSI and the numerous constraints and conflicts in these environments make GSI siting and installation challenging, time consuming and prone to error. We present our innovative solution — a better way to identify GSI locations in your dense urban environment. Solution — Our team developed a tool (Using ArcGIS Model Builder and Python Scripting) to assist with determining the feasibility of installing GSI across the entire City of Somerville in Massachusetts — the most densely populated municipality in New England. Somerville has a population of approximately 80,000 people within its four square miles — that's about 20,000 people per square mile. This tool utilizes available GIS layers, topographic data, and satellite imagery data to identify potential GSI candidate areas on the public right-of-way (roadway, sidewalks, and other general areas such as parks) based on cumulative siting parameters that apply to each GSI solution. In the case of the City of Somerville, to be considered eligible for consideration of a GSI install, a location must meet all of thirteen separate criteria such as minimum clearance from existing utilities, buildings, crosswalks/driveways, trees and parking meters, appropriate ground surface slope, with appropriate soil types. Only when all of these criteria are met is a location considered eligible. Determining this intersection of criteria meeting is very time consuming in the traditional manner — (using multiple separate data sources with a trial-and-error approach — particularly in a dense urban environment - the 'Reactive Approach' [Figure 2].). A simplified 'Venn Diagram [Figure 1]' approach, using only 5 of the 13 criteria, will be presented to portray the challenges of finding eligible locations. Only the gray section at the center of the Venn Diagram represents areas meeting all 5 criteria. The innovative tool identifies locations within the City (or parts of the City) that meet all of the siting criteria ('Proactive Approach' - Figure 3 shows a section of the City with the tool applied. Only the areas shaded in green meet all of the 13 GSI criteria. — and are therefore eligible for GSI siting consideration.) In dense urban environments, these sites are often few and far between — essentially like looking for a 'needle in a haystack'. Use of the tool avoids the need for an iterative/inefficient 'manual/reactive' approach to identifying these locations. Boots-on-the-ground are still needed to make the 'final call' on appropriateness of each location identified by the tool — allowing Engineer and the City to focus efforts on application of engineering judgement and stakeholder concerns and not on the trial-and-error process for initial location clearance. This significantly reduced the amount of time and effort it would have taken to perform a preliminary/traditional GSI Siting analysis City-wide. This tool can be adapted and scaled for use with other municipalities and for other siting analyses (utility siting, environmental permitting, etc.) This presentation will compare the approach, process and benefits of the newly developed application/tool with traditionally-used approaches. Key Aspects: -An efficient and accurate preliminary GSI siting analysis -Simplified analysis, using existing data sets and reducing field work -Customizable for different GSI Siting criteria -Adaptable and scalable for other siting analyses types Participants in this presentation will develop an understanding of gray vs green infrastructure, the types of Green infrastructure appropriate for dense urban environments, the multiple criteria that must be met for a location to be considered eligible for GSI siting, the application of the siting tool, and potential enhancements to the tool as well as other potential uses for this type of innovative approach.