Legacy sediments are those sediments that have accumulated behind dams built on streams in the late 17th through mid 19th centuries to provide water power to run various types of mills (e.g., grain, sawmill).
These defunct and mostly in-place dams have resulted in radical modifications to streams, including unnatural high stream bank walls and stream and wetland contours; an historic loss of wetlands; and excess sediment scouring during storm events with a resultant increase loading of nutrients and sediments downstream.
Legacy sediments provide opportunities to significantly improve stream water quality, increase riparian wetlands, and reduce nutrient and sediment loads downstream. Approaches to stream restoration used today typically do not account for legacy sediments and may fail or, in fact, exacerbate sedimentation problems.
Online Video: Mark Gutshall, LandStudies, Talks About Legacy Sediments
This workshop will discuss legacy sediment impacts, opportunities for mitigation, restoration techniques, and implications to aquatic resource programs.