A critical element of controlling sediment discharges from roads is to apply storm-proofing treatments. In their Updated Handbook for Forest, Ranch, and Rural Roads, Pacific Watershed Associates have prepared a list of storm-proofed roads characteristics. That list is reproduced below.

Storm-proofed Stream Crossings:

• All stream crossings have a drainage structure designed for the 100-year flood flow (including woody debris and sediment).
• Stream crossings have no diversion potential (functional critical dips are in place).
• Culvert inlets have low plug potential (trash barriers or deflectors are installed where needed).
• Culverts are installed at the base of the fill and in line with the natural channel.
• Any existing culverts or new emergency overflow culverts that emerge higher in the fill have full round, anchored downspouts that extend to the natural channel.
• Stream crossing culvert outlets are protected from erosion (extend culverts at least 6 feet beyond the base of the fill and use energy dissipation, where needed).
• Culvert inlet, outlet and bottom are open and in sound condition.
• Deep fills (deeper than a backhoe can reach from the roadbed) with undersized culverts or culverts with high plugging potential are fitted with an emergency overflow culvert.
• Bridges have stable, non-eroding abutments and do not significantly restrict 100-year flood flow.
• Stream crossing fills are stable (unstable fills are removed or stabilized).
• Approaching road surfaces and ditches are “disconnected” from streams and stream crossing culverts to the maximum extent feasible using road shaping and road drainage structures.
• Class I (fish-bearing) stream crossings meet State Fish and Wildlife and National Marine Fisheries Service fish passage criteria.
• Decommissioned stream crossings are excavated to exhume the original, stable, stream bed and channel sideslopes, and then stabilized with mulch and vegetation.

Storm-proofed Road and Landing Fills:

• Unstable and potentially unstable road and landing fills that could deliver sediment to a stream are excavated (removed) or structurally stabilized.
• Excavated spoil is placed in locations where eroded material will not enter a stream.
• Excavated spoil is placed where it will not cause a slope failure or landslide.

Storm-proofed Road Surface Drainage:

• Road surfaces and ditches are hydrologically “disconnected” from streams and stream crossing culverts. Road surface runoff is dispersed, rather than collected and concentrated.
• Ditches are drained frequently by functional ditch relief culverts, rolling dips or cross road drains.
• Outflow from ditch relief culverts does not discharge to streams.
• Ditch relief culverts with gullies that deliver to a stream are removed or dewatered.
• Ditches and road surface drainage does not discharge (through culverts, rolling dips or other cross drains) onto active or potential landslides.
• Decommissioned roads have permanent drainage and do not rely on ditches.
• Fine sediment contributions from roads, cutbanks and ditches are minimized by utilizing seasonal closures and installing a variety of surface drainage techniques including berm removal, road surface shaping (outsloping, insloping or crowning), rolling dips, ditch relief culverts, waterbars and other measures to disperse road surface runoff and reduce or eliminate sediment delivery to the stream.