Lateral Log-jam Structures (LLJ)

Lateral structure usually fall under one of two designs:

Single-log: a log is placed so that it projects from the bank into the stream. Attached to a tree or stump on the bank, the log is ballasted with one or two boulders in the stream channel to prevent movement, especially at high flows. Also, a group of single logs with rootwads can be complexed.

Traingular: consists of two logs attached separately to trees or stumps on the bank and both are ballasted by a common anchor or boulder in the stream. Additional LWD and rootwats can be added once basic structure is complete. Versions of the triangular complex seem to be more stable than single-log jams and can also provide more habitat. In construction of these structure one should keep in mind that;

• larger boulder should be placed at the upstream side of the log
• a fastening and boulder ballast system is required to prevent dislodging of LWD
• commonly utilized is high strength galvanized cable secured with epoxy resin
• it is helpful to use Design Charts to determine ballast requirements.

Lateral structures:

• consist of logs and rootwads secured to large boulders, aligned or angled with the stream banks, and attached to tree bases or stumps
• are placed at residual pool sites that had already contained natural LWD accumulations of a similar nature.
• can serve to armour eroding banks when installed at sharp bends
• are useful in catching debris and organic material
• over time will scour deep pools for habitat and refuge.
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