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).
Showing posts with label sediment. Show all posts
Showing posts with label sediment. Show all posts
January 1, 2006
September 4, 2005
Road Drainage
By Thembi Borras
Chances are you have seen the result of poor road drainage manifested in water that has been allowed to concentrate and reach a velocity that moves soil causing accelerated erosion. Addressing road drainage is central to meeting two of the road management goals, reducing chronic delivery of sediment and reducing maintenance.
There are three ways to drain a road. Insloping is where the roadbed is tipped toward the cutbank, water flows to the inside ditch where it mixes with flow intercepted from the hillslope. The water is then carried to a ditch relief culvert and underneath the road to the outside edge of the road. Outsloping is where the roadbed is tipped out; water is not concentrated and flows to the outside edge of the road. Rolling dips supplement outsloping by insuring water gets across the road. The third way to drain a road is crowning, 1/2 the roadbed is tipped out and 1/2 the roadbed is tipped in.
Any of these methods, installed well, will minimize chronic erosion. The key is to drain roads well and frequently onto stable surfaces.
After road improvement, chronic erosion will continue. However, improvements are intended to minimize and redirect the sediment generated to stable locations and filter strips, such that the sediment has a chance to drop out before reaching the waterway, thus disconnecting roads from streams.
For more information on road drainage reference the Handbook for Forest and Ranch Roads by Pacific Watershed Associates or the "Roads" video, adapted from the Handbook. Both are available through the Mendocino County Resource Conservation District (707-468-9223) and the Navarro River Resource Center (707-895-3230).
Chances are you have seen the result of poor road drainage manifested in water that has been allowed to concentrate and reach a velocity that moves soil causing accelerated erosion. Addressing road drainage is central to meeting two of the road management goals, reducing chronic delivery of sediment and reducing maintenance.
There are three ways to drain a road. Insloping is where the roadbed is tipped toward the cutbank, water flows to the inside ditch where it mixes with flow intercepted from the hillslope. The water is then carried to a ditch relief culvert and underneath the road to the outside edge of the road. Outsloping is where the roadbed is tipped out; water is not concentrated and flows to the outside edge of the road. Rolling dips supplement outsloping by insuring water gets across the road. The third way to drain a road is crowning, 1/2 the roadbed is tipped out and 1/2 the roadbed is tipped in.
Any of these methods, installed well, will minimize chronic erosion. The key is to drain roads well and frequently onto stable surfaces.
After road improvement, chronic erosion will continue. However, improvements are intended to minimize and redirect the sediment generated to stable locations and filter strips, such that the sediment has a chance to drop out before reaching the waterway, thus disconnecting roads from streams.
For more information on road drainage reference the Handbook for Forest and Ranch Roads by Pacific Watershed Associates or the "Roads" video, adapted from the Handbook. Both are available through the Mendocino County Resource Conservation District (707-468-9223) and the Navarro River Resource Center (707-895-3230).
August 21, 2005
Roads
By Thembi Borras
Roads facilitate travel to our homes and places of work. In fact, nearly every activity in a rural community requires getting in a car and traveling on a road somewhere. In a logging operation roads influence aesthetics, logging costs and environmental mitigation. I often find myself asking the question, can an existing problem road, located near a watercourse, be relocated to a ridge and diminish the environmental consequences at the same time facilitate logging method and be financially feasible? During my forestry fieldwork, second only to deciding what trees will be left and cut, is managing roads for improvement and aesthetics. I have yet to meet a road that did not need improvement. Why should you be concerned about roads? Because poorly constructed roads accelerate erosion, which increases stream sedimentation, and can be maintenance nightmares.
According to Danny Hagans of Pacific Watershed Associates the three goals of road improvement are to reduce the chance of sediment delivery as a result of episodic events, reduce chronic delivery of sediment and reduce maintenance. There are many ways to accomplish these goals. Addressing the following points in your road management decisions will insure the ultimate goal, of making roads as invisible on the landscape as possible, is met. Drain roads well and frequently onto stable surfaces, diversion proof crossings, design crossings to pass fish and design crossings for the large episodic event.
There are resources to aid you in road management decision making. A widely used publication is the Handbook for Forest and Ranch Roads by Pacific Watershed Associates. The concepts in the Handbook have been adapted into a "Roads" video. Both are available through the Mendocino County Resource Conservation District (707-468-9223) and the Navarro River Resource Center (707-895-3230). Also check out the website of the Navarro Watershed Working Group (http://www.nwwg.org/) and click on workshops. There you will find a comprehensive write-up from a 2003 Roads workshop.
Roads facilitate travel to our homes and places of work. In fact, nearly every activity in a rural community requires getting in a car and traveling on a road somewhere. In a logging operation roads influence aesthetics, logging costs and environmental mitigation. I often find myself asking the question, can an existing problem road, located near a watercourse, be relocated to a ridge and diminish the environmental consequences at the same time facilitate logging method and be financially feasible? During my forestry fieldwork, second only to deciding what trees will be left and cut, is managing roads for improvement and aesthetics. I have yet to meet a road that did not need improvement. Why should you be concerned about roads? Because poorly constructed roads accelerate erosion, which increases stream sedimentation, and can be maintenance nightmares.
According to Danny Hagans of Pacific Watershed Associates the three goals of road improvement are to reduce the chance of sediment delivery as a result of episodic events, reduce chronic delivery of sediment and reduce maintenance. There are many ways to accomplish these goals. Addressing the following points in your road management decisions will insure the ultimate goal, of making roads as invisible on the landscape as possible, is met. Drain roads well and frequently onto stable surfaces, diversion proof crossings, design crossings to pass fish and design crossings for the large episodic event.
There are resources to aid you in road management decision making. A widely used publication is the Handbook for Forest and Ranch Roads by Pacific Watershed Associates. The concepts in the Handbook have been adapted into a "Roads" video. Both are available through the Mendocino County Resource Conservation District (707-468-9223) and the Navarro River Resource Center (707-895-3230). Also check out the website of the Navarro Watershed Working Group (http://www.nwwg.org/) and click on workshops. There you will find a comprehensive write-up from a 2003 Roads workshop.
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