‹ back to GIS Glossary

Stormwater Management Mapping

Definition

Stormwater management mapping inventories drainage infrastructure and models how rainfall moves through urban catchments. It integrates inlets, pipes, manholes, detention basins, green infrastructure, terrain, land cover, and soils. Maps support maintenance, regulatory reporting, capital planning, and flood mitigation. Hydrologic-hydraulic models simulate peak flows, surcharge, and overland flow paths when capacity is exceeded.

Application

Cities use these maps to prioritize cleaning of inlets, to design retrofits that reduce combined sewer overflows, and to target green streets. Developers demonstrate compliance with runoff limits. Emergency teams plan road closures for intense storms. Public portals communicate risk and allow residents to report blocked drains with photos linked to assets.

FAQ

How do you represent dual drainage (pipes plus surface flow) realistically?

Couple 1D pipe networks with 2D overland flow on a high-resolution DEM; connect inlets as exchange points so overflow routes to streets and low spots are captured.

What data quality issues commonly undermine stormwater maps?

Unknown pipe inverts, missing private laterals, and outdated as-builts. Field surveys and CCTV inspections fill gaps; attribute confidence scores flag uncertain segments.

How can green infrastructure be modeled at city scale?

Represent bioretention and permeable surfaces as reductions in effective imperviousness or as storage nodes with infiltration parameters calibrated from pilot sites.

What metrics help communicate program success?

Inches of runoff captured, CSO events avoided, flooded-intersection hours reduced, and maintenance backlog cleared—reported by basin and year to show progress.