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Each year, 370 billion gallons of untreated stormwater enters Puget Sound's streams, rivers, lakes, and marine waters. Untreated stormwater carries a soup of pollutants generated on the land surface and concentrated into waterways from a decentralized network of roads, aging and over-burdened sewer pipes, and impervious, urbanized landscapes.

As the leading contributor of toxic pollutants to Puget Sound waters, untreated stormwater runoff is a key ecological problem that has harmed virtually all urban and urbanizing streams and rivers, as well as the waters of Puget Sound. As a result, the abundance, health, and survival of aquatic and marine species has declined at all levels of the food web, including the region's iconic orca whales. Human health is also suffering as we live out our lives adjacent to near-ubiquitous pollution. Communities of color are most at risk, here and around the world, of living near contaminated air, water, and soil.

The Stormwater Heatmap was designed to help communities take targeted, high-impact action on rolling back this legacy of pollution. The heatmap harnesses the power of machine learning, cloud computing, innovative traffic modeling, and long-term spatial datasets to predictively map where stormwater pollution is generated across the landscape. We generated three main components that combine to create the Stormwater Heatmap: 1) a high resolution land cover spatial dataset for the Puget Sound watershed; 2) a process-based hydrology model drawing from over one million timesteps of climate data; and 3) statistical models relating a decade of local water quality testing results to Puget Sound spatial datasets. From Olympia to Bellingham and Snoqualmie Pass to Neah Bay, the stormwater heatmap metrics can be used to help prioritize green and grey infrastructure investments in key hotspot locations across the landscape. This is the first step to prioritizing high-impact investment in green stormwater infrastructure.

What is the Stormwater Heatmap?

The Stormwater Heatmap is an interactive mapping tool, report generator, and data repository that quantitatively visualizes hotspots of pollution generation and runoff throughout the Puget Sound watershed.

The mapping tool is designed to support stormwater planning at multiple scales- from large watershed to local neighborhoods. The pollution heatmaps provide new and rigorous insight into where stormwater infrastructure investments are needed in order to buffer against the adverse environmental impacts of stormwater pollution to people and nature.

All spatial data layers, images, and reports are downloadable for use outside of the online tool, and all code is open source. Included in this heatmap is data on precipitation, landcover, landuse, soils, hydrology output, and a variety of other datasets. To learn more about the foundational data layers in this heatmap, visit the technical report page of this website.

Please note: the pollution heatmap models are best suited for strategic management decisions wherein the relative loading of different pollutants is more important than the estimated load quantity itself.

Stormwater Heatmap development

This tool was developed by The Nature Conservancy, Geosyntec Consultants, and Cheva Consultants, with collaboration from the University of Washington Climate Impacts Group, the Washington Department of Fish & Wildlife, and the NOAA Office of Coastal Management. Funding was provided by The Boeing Company.

The Stormwater Heatmap was conceptualized by The Nature Conservancy- preserving and protecting the land and waters upon which all life depends.