In Ann Arbor, all stormwater (and any pollutants carried by storm water) are discharged, untreated, to the Huron River and its tributaries.
The stormwater infrastructure in Ann Arbor consists of:
Over 541 miles of stormwater ditches and underground pipes.
- Over 23,000 inlets and catch basins.
- 51,926 city-managed trees (and counting).
- 70 city-owned rain gardens.
- 1,123 residential rain barrels (and counting).
Residents can help by:
Why is stormwater a problem?
Both the quantity and quality of stormwater runoff can negatively impact the local water resources that provide drinking water, recreation and wildlife habitat.
- Water Quantity - Once land is urbanized, very little water is able to infiltrate into the ground, and instead, is rapidly conveyed via storm drains or surface runoff to the nearest water resource. Higher volumes of stormwater runoff can cause flooding, erosion, and property damage.
- Water Quality - Stormwater runoff picks up anything in its path and delivers it to the nearest creek or river.
Urban watersheds typically exhibit:
- Increased run-off volume due to greater impervious surface and lower tree canopy
- Increased peak discharge rates due to highly efficient drainage systems
- Diminished baseflow, or dry weather flow, due to decreased groundwater infiltration
The City of Ann Arbor works to manage stormwater in conjunction with land use change in order to protect water quality and reduce impacts of stormwater on local water resources.
What is the City doing?
Plans, designs, constructs and maintains a stormwater management system, sediment/flood control programs and projects, and provides stormwater education.
View an interactive
Green Infrastructure Map, showing many of the Green Infrastructure project the City has accomplished with Stormwater Utility funds. The map also shows projects completed by the Washtenaw County Water Resources Commissioner, Huron River Watershed Council, and the University of Michigan.
Resources for Low Impact Development and Stormwater Best Management Practices.
Stormwater rates and credits
Learn about Ann Arbor's tiered
stormwater rate structure, which is based on a property's amount of impervious surface.
Credits could help property owners reduce their rates.
Find out how the City of Ann Arbor works with other Middle Huron River Watershed
partners to meet
state and federal stormwater permit regulations.
Stormwater Management Requirements for Residential Construction
A stormwater management plan is required for residential construction projects with 200+ sq. ft. of impervious surfaces. Learn about the code changes and download an impervious area worksheet to determine the code affects your project.