MS4 Stormwater Compliance

A High Definition Stream Survey will reduce your long-term MS4 compliance costs.

Fundamental to achieving clean water standards is understanding the context, distribution and severity of the problems in your streams and developing effective long-term plans to address them. But collecting this information is time consuming and expensive, which makes effective clean water planning very difficult.  A High Definition Stream Survey (HDSS) is a complete system to rapidly document stream and outfall conditions.  It will provide information necessary to more effectively manage the stormwater component of cleaner water. 

The HDSS Methodology

Under the National Pollutant Discharge Elimination Standards (NPDES), Municipal Separate Storm Sewer Systems (MS4) require specific data to complete the permitting process. The high definition stream survey technique (HDSS) provides this critical data and more accurately represents conditions within the stream corridor when compared to traditional methods. This is possible because HDSS is the only method that provides continuous, reviewable data over the entire corridor.

HDSS documents continous and discrete variables throughout a stream corridor.

Rehabilitation Scoring

“Rehabilitation scoring” allows stormwater managers to compare the relative cost/benefit of different restoration BMP strategies designed to address problems in an MS4 receiving stream system. Managers can then objectively prioritize restoration efforts within a given range of budget and resource contstraints. Rehabilitation Scores take into account restoration BMP costs and the potential functional uplift that could be achieved with those BMPs. Such BMPs could range from inexpensive (simple tree planting and streamside cleanup done with volunteers) to expensive (total stream restorations requiring engineering, permits and heavy equipment). Contact us to learn more about how Rehabilitation Scoring will enhance the utility of your MS4 stream assessments.

Data Parameters

HDSS data is geo-referenced as continuous or point data with condition and type identified. 

Continuous data (streambeds, streambanks, and riparian zones) are scored on the basis of 01) condition and 2) type (degree of modification).

MS4 webpage 1
HDSS video shows how continous variable condition and type changes over any stretch of stream.

Point data are discrete man-made or natural features (exposed pipes, road crossings, sedimentation, fish barriers, trash, etc.) that may affect the physical and biological function of the stream corridor. Point data are scored for 1) condition and 2) type.

HDSS is easily adaptable to existing assessment protocols and has been successfully applied to the Maryland Stream Corridor Assessment protocol (Yetman, 2001). Unlike a typical “windshield” survey, HDSS documents continuous and point variables over the entire MS4 watershed with continuous video coverage. Additionally, video documentation makes it possible for multiple stakeholders to remotely review issues at their convenience.

Discrete variables.
Examples of a few types of point data: exposed pipe (A), road crossing (B), sedimentation (C & D), fish barrier (E), and incoming channel (F).

The stormwater mapping requirement in MS4 permit compliance is an opportunity to develop information applicable to many different purposes beyond just MS4 compliance. Using HDSS for your MS4 watershed planning mapping will provide your partners and other interested parties with the data and mapping foundation needed for habitat assessments, dam removal and stream restoration projects, impact assessments, water quality sampling, instream flow modeling, TMDL studies, source water protection planning and much more. The breadth of information provided in a single HDSS application will reduce the long-term costs of water-based compliance issues.