Stormwater management professionals and GIS experts often face the daunting task of delineating MS4 drainage catchments for regulatory compliance and effective urban water management. In this webinar, 2NDNATURE’s experts shared valuable tips for using ArcGIS Pro to streamline the delineation process, save time, and integrate catchments into stormwater management programs.
Why Catchments Matter for MS4 Programs
Urban catchments are the foundation of effective stormwater management. They refine larger watersheds into smaller, hydrologically connected areas, enabling municipalities to:
- Track pollutant loads impacting receiving waters.
- Prioritize BMPs (Best Management Practices) for maximum pollution reduction.
- Streamline compliance with MS4 and NPDES permits.
By tying stormwater actions to measurable impacts, catchments provide a straightforward way to demonstrate program success to regulators, city councils, and the public.
4 Tips for Delineating Catchments in ArcGIS Pro
1. Utilize ArcGIS Living Atlas for Authoritative Data
The ArcGIS Living Atlas of the World is a treasure trove of high-quality, national-scale datasets. Start with these three essential layers:
- Watershed Boundaries: Understand the larger hydrologic context.
- Water Bodies and Streams: Identify receiving waters.
- Contours or Elevation Data: Use DEMs or slope layers to define drainage areas.
These datasets are readily available within ArcGIS Pro, allowing you to build a foundation for catchment delineation quickly.
2. Leverage Existing Local Data
Collaborating with your GIS team is essential. To improve accuracy, utilize local data on stormwater infrastructure—such as outfalls, storm drains, and channels. Visualizing attributes like pipe diameter or outfall size can aid in prioritizing catchment delineation.
Pro Tip: Larger outfalls often indicate larger drainage areas, making them an ideal starting point.
3. Master ArcGIS Pro Editing Tools
ArcGIS Pro provides powerful tools for refining catchments. The Split Tool allows users to divide watersheds into smaller, actionable catchments. The Merge Tool refines boundaries, ensuring accuracy without overlaps or gaps. By combining these tools, users can create a seamless, well-organized representation of watersheds tailored to their specific project needs. Check out the webinar recording to see how our team uses these tools.
Example: Adjust catchment boundaries to align with roads or storm drain paths for more precise mapping.
4. Switch Between Imagery and Topographic Base Maps
To maintain spatial context, toggle between imagery and topographic maps. Imagery provides insight into neighborhoods and land use, while topographic maps highlight elevation changes critical to delineation.
Real-World Application: Using Catchments in 2NFORM
2NFORM is the leading stormwater management software utilized by MS4 programs and non-traditional NPDES permit holders throughout the United States. It helps users maintain an accurate inventory of their stormwater assets, conduct inspections, and streamline annual reporting requirements. By digitizing your urban catchments, you can efficiently organize your activities and reporting processes. Here’s how:
- Pollution Reduction Modeling: Catchments enable precise modeling of baseline pollutant loads and BMP effectiveness. The software aggregates GIS data, such as rainfall, impervious surfaces, and land use, to calculate particulate loads at the catchment level.
- Opportunity Mapping: Identify high-priority areas for BMP implementation, such as green infrastructure retrofits, by overlaying pollutant reduction potential with city infrastructure data.
- Automated Reporting: Catchments tie stormwater actions—like street sweeping or structural BMP maintenance—to measurable outcomes, simplifying annual reporting for MS4 compliance.
Transform Your Catchment Delineation Process
By integrating ArcGIS Pro with 2NFORM’s geospatial capabilities, municipalities can optimize catchment delineation, enhance regulatory compliance, and improve water quality outcomes.
Ready to elevate your stormwater program? Watch the webinar to learn about ArcGIS Pro tools and 2NFORM’s applications.