Evaluation of erosion control BMPs on ditched haul road stream crossing approaches following reconstruction.
Ditched forest roads leading to stream crossings and used for log transportation have recently been a topic of water quality concern and legal controversy. Best management practices (BMPs) can reduce potential water quality issues, yet few research studies have quantified BMP costs and reductions in sediment from implementing specific ditch BMPs. Researchers reconstructed fifty 15.2 m sections of ditches at stream crossings or cross drains and applied one of five treatments. Treatments were replicated 10 times and split by two slope classes in a completely randomized design. Silt fence traps were placed at the end of each ditch section prior to stream crossings or culvert inlets. Sediment pins were installed adjacent to the silt fence and sediment deposit depths were measured 42 days following ditch re-construction. Field based results show that median erosion rates were greatest for the Bare (48.0 Mg ha-1 yr-1), followed by Seeded (25.0 Mg ha-1 yr-1), Check Dams (22.2 Mg ha-1 yr-1), Completely Rocked (2.6 Mg ha-1 yr-1), and Seeded with Erosion Mat (2.1 Mg ha-1 yr-1). Results from the Kruskal-Wallis statistical test showed that the Bare treatments had significantly greater erosion rates from Completely Rocked and Seeded with Erosion Mat treatments. Cost of BMP treatment was cheapest for Seeded ($9), followed by Seeded with Erosion Mat ($24), Check Dams ($45.40), and Completely Rocked ($119.50). Study results suggest that re-constructed ditches should drain short sections of road and should contain some erosion control BMP in order to reduce erosion and sediment delivery.