Log Weir

{
  "id": "MLC-T-ENV-016006",
  "term": "Log Weir",
  "field": "Environment",
  "definition": "consists of a header log and a footer log placed in the bed of the stream channel, perpendicular or at an angle to stream flow, depending on the size of the stream. The logs extend into the stream banks on both sides of the structure to prevent erosion and bypassing of the structure. The logs are installed flush with the channel bottom upstream of the log. The footer log is placed to the depth of scour expected, to prevent the structure from being undermined. This weir structure creates a “step” - or abrupt drop in water surface elevation - that serves the same functions as a natural step created from bedrock or a log that has fallen into the stream. The weir typically forms a very deep pool just downstream, due to the scour energy of the water dropping over the step. Weirs are typically installed with a maximum height of 3 to 6 inches so that fish passage is not impaired. Log weirs provide bedform diversity, maintain channel profile, and provide pool and cover habitat.",
  "references": [
    "EPA and DOI Fish and Wildlife Service Natural Channel Design Review Checklist Stream Mechanics at http://water.epa.gov/lawsregs/guidance/wetlands/upload/Natural_Channel_Design_Checklist_5_16_12.pdf"
  ],
  "url": "https://mlchart.com/terminology/environment/log-weir/"
}