Mill Creek Tributary Step Pool Conveyance System

What is polluted runoff?

Parts of the Chesapeake Bay watershed contain a high percentage of impervious cover – paved or other hard surfaces such as roofs and roadways that prevent rain water from being absorbed into the ground.  Instead, water runs along these surfaces, collecting trash and substances such as motor oil, lawn fertilizers, and pesticides.  This polluted stormwater flows into streams and rivers, where it threatens aquatic ecosystems and public health.  

Effective stormwater management, on the other hand, creates safe paths for polluted runoff to be captured and filtered through the ground before it reaches waterways.  This helps keep the environment clean and our communities healthy!

stream restoration
before image
Prior to restoration, streambanks were extremely eroded. Credit: Anne Arundel County.
after image
The restored stream provides stable channel conditions. Credit: Anne Arundel County.


Problem: A 600-foot tributary to Mill Creek had become severely eroded and was starting to undermine the integrity of structures in the surrounding area. The degraded tributary was damaging property values, endangering community assets, and contributing polluted waters to the Magothy River. 

Solution: Using proceeds from its Watershed Protection and Restoration Program, Anne Arundel County installed a Regenerative Step Pool Storm Conveyance System (SPSC) to stabilize channel conditions and protect the homes of adjacent landowners. The system reconnected the stream to its floodplain and enhanced the nutrient uptake of the stream and wetland system.  

Scale: 600 linear feet treating runoff from 18.2 acres

Pollutants removed: 27.5 lbs/yr nitrogen; 34 lbs/yr phosphorous; 62 tons/yr sediment

Cost: $217,000

Funding sources:  Anne Arundel County’s Watershed Protection and Restoration Program fees; MD Department of Natural Resources

More information:


Contact Information
Robb Fish | WPRP Anne Arundel County | 410-222-4240 | E-mail:
Key project facts
Project Type
Stream Restoration
Project Scale
$100,000 - $249,999
Story Focus
Environmental Benefits
Stormwater Funds
Problem Addressed
Runoff Pollution
Year Installed
State Legislative District
Federal Legislative District
MD 4th