Debris traps are constructed in rivers to catch debris with a high risk of mobilising in a flood. They are often made from rammed railway irons or steel beams threaded with wire rope and anchored solidly at each end. They should be engineered. They can easily fail. Debris traps installed into a riverbed require a resource consent.
- Debris trap doing its job well but needs to be cleaned out
- Beams spaced at 1.5 to 2 m
- Beams were driven in more than 1.5 m
- 22 mm wire rope was threaded through the beams
- Wire rope was securely anchored then tensioned
- Constructed to protect a culvert
- Put directly across the river
- Easy to clean out
- Fish passage is not blocked
- Water can flow freely
- Debris traps need to last at least six years
- Locate in a flat section of the river to reduce the risk of it failing
- A poor debris trap anchor caused it to fail
- Consider putting debris traps in the side streams
- Debris trap failures could lead to lots of wood going downstream at once, causing significant damage