What are the benefits and disadvantages of digger logs?

Digger logs provide desirable scouring and sorting of channel materials, creating or enhancing an existing pool downstream of a riffle. They provide pool habitat for fish, support larger insect populations, and create a low velocity resting place with overhead cover and shade. Digger logs can be built with on-site materials in remote or poorly accessible areas, and are simple to design and effective at creating desirable fish habitat. However, they can cause bank erosion and the formation of unwanted silt bars downstream of the structure, as well as trap debris and cause debris dams to form. They may also disturb habitat if not positioned and anchored correctly.