Example photos (provided by SA Water) of coir log leaky weirs at Middle River Reservoir (post-fire) before and after a 50 mm rain most of which fell in 20 minutes.
The logs worked very well, a total of ten such leaky weirs structures pulled up an estimated 200 ton of silt. Would have trapped a lot more silt if not for the rocky substrate preventing us binding them down tighter together. We gave up on hardwood stakes (preferred as they are biodegradable) and used metal droppers with a petrol-powered auger, but even then we couldn’t get the droppers in as deep as we would have liked. Usually drainage lines are not quite so rocky.
Shaun, Vegetation Services Specialist, SA Water