Stream Mitigation: a New Approach on the Texas Coastal Plain

Historically, compensation for impacts to streams regulated by the Clean Water Act in the U.S. Army Corps of Engineers–Galveston District were mitigated out-of-kind with wetland restoration.  However, revisions in 2008 to compensatory mitigation regulations (33 CFR 332) now require in-kind mitigation for stream impacts. A multi-agency workgroup has developed a stream tool to assess stream condition and to determine required compensation credits within the Galveston District.  Stream condition is assessed on a tiered basis according to duration of streamflow – ephemeral and intermittent streams, intermittent streams with perennial pools, and perennial streams.  All tiers evaluate channel condition, riparian buffer, in-stream habitat, and channel alteration.  The intermittent streams with perennial pools tier adds a fish IBI variable. The perennial streams tier includes the fish IBI variable and adds a macroinvertebrate variable.  The stream tool also assesses proposed impacts based on the severity to which they are expected to impair the stream (e.g., channelization vs. culverts).  Varying amounts of mitigation credits are generated according to the type of restoration activities selected.  Challenges of developing a stream functional assessment, such as balancing vested agency interests and regulatory needs, will be discussed.