Is your road up to the big, fast water challenge?

By Thembi Borras

The winter storms are delivering big, fast water causing some stream crossings to fail, road rock to be lost, sink holes and road failures. Well designed roads and stream crossings take into account large storm events. Moreover, when well designed roads and stream crossings are properly constructed and installed, they are better able to resist the big, fast and infrequent water as we have been having. The best time to determine if your road is holding up to the big, fast water challenge is during the storm. If it is not safe, you can often project, where the high water level was, based on debris, mudlines and waterlines, after the storm.

Indicators that your road is not adequately drained include waving farewell to your road rock, the capacity of your ditch relief culverts and inside ditches are being exceeded and rills are forming in your road bed.

An indicator that your culverted stream crossing is not adequately designed is the capacity of the culvert is being exceeded. Plugging is often evidence that a culvert is undersized. When a stream crossing plugs it can spell bad news. In the winter of 1995/1996 an undersized culvert plugged on our private dirt road. The diverted water traveled 125 yards where it outleted carrying 30 cubic yards of the roadbed to the creek, facilitated by the well formed berm on the outside edge of the road.

At the same time your are evaluating your road during a storm you can do effective short-term maintenance, with a shovel or a hoe, that will protect your investment. Dig ditches to get the water off the road as quickly as possible and deliver it to a stable location. Remove any blockages from culvert inlets. Clear your inside ditches of debris but keep growing things in the ditch, to slow the water and meter sediment, unless you need the capacity. Long term fixes include sizing your stream crossings for 100 year storm events and where appropriate can include replacing culverts with rock armored fill crossings, installing more frequent cross drainage and reshaping roads to have outslope.

In the spring, remember the big fast water of 12-30-05 and ask yourself if your road could be improved, it may not be cheap, but it could save you money and inconvenience in the end. Remember the goals of road improvement are to reduce the chance of sediment delivery because of episodic events, reduce chronic delivery of sediment and reduce maintenance.

The Handbook for Forest and Ranch Roads by Pacific Watershed Associates will aid you in your road management decision making and is available through the Mendocino County Resource Conservation District (707-468-9223) and the Navarro River Resource Center (707-895-3230).