Stream Health

Current Stream Health Overview

The Maryland Biological Stream Survey uses a “stratified random design” in determining sampling locations. First, the number of sites needed to be sampled in order to estimate the stream health of the watershed within a known statistical accuracy is determined based on the number of stream miles within the watershed. Next, a computer program randomly selects sites on streams in that watershed for sampling. Department staff then contact the landowners to receive permission to access the sites from their property.

Stream Health Map


After all the sites in the watershed have been sampled, the results are then compiled to assign an overall rating of “good”, “fair”, or “poor” for streams in the watershed. It is important to note that stream health can vary considerably from location to location within a watershed based on activity on the adjacent land. As a result, there may be several “good” sites in an overall “poor” watershed and visa versa.