An expensive road to nowhere?

Road erosion and washouts are a problem for many residents of Trinity County.  This is especially true for those living along unpaved roads in the more mountainous areas.  Steep slopes and heavy rainfall (or rain on snow) combine to cause soil instability, erosion, and drainage problems which can pollute streams with sediment, damage or destroy roads, and threaten other property as well. 

Roads increase soil erosion by the alteration of natural drainage patterns.  One of the main mechanisms by which this is done is through collection/concentration of runoff from the hillside.  In many instances roads collect water from a wide area of hillslope, runoff that would normally be diffused across the land on its way down to a waterway below.  However, a road may create a kind of dam, an unnatural barrier at which all of the water is stopped, then redirected (by means of an inboard ditch for example).   Thus a large amount of water is concentrated at specific crossing points, often the site of a natural stream crossing.  This concentration of runoff increases the likelihood of culvert failures due to debris and sediment and other problems during storm events.  Such failures create environmental damage and necessitate costly repairs.  The cost of repairs to a failed road greatly outweighs the costs of regular upkeep and preventive maintenance. 

Another problem that is compounded by collection/concentration of runoff is the increased amount of sediment that is delivered to our streams and rivers.  Roads are much more prone to erosion than the undisturbed land on which they were built, due to the disturbances in hillslope continuity and vegetative cover.  Runoff water picks up exposed soil as it passes over, and delivers it in concentrated form to the road’s stream crossings.  When these crossings are natural creeks or other waterways, then all of this extra sediment is being delivered  directly into the region’s stream and river system.  This has significant impact on the salmon habitat in our County and the lands of our downstream neighbors—sediment settles out in the streams and rivers and chokes the spawning gravels that are vital for salmon reproduction.  Increased turbidity (sediment content) in our  waters harms not only salmon and other native fishes, but also ourselves, as it fills up dams, clouds our drinking water, and carries our fertile soils out to sea. 

Unpaved roads are major contributors of sheet, rill and gully erosion, as well as landslide erosion.  Paved roads, however, are also a significant problem.  Cutbanks, plugged culverts, and increased concentration of water runoff raise erosion rates and sedimentation. 

The US Environmental Protection Agency (EPA), through its Total Maximum Daily Load (TMDL) process, as well as other regulatory agencies, are showing concerns about the high levels of sediment reaching both the South Fork and mainstem Trinity Rivers.  Most counties have enacted some type of grading ordinance to be able to achieve proper road and building grading techniques in order to reduce erosion. 

Failed culverts are a common road-related problem

Steps taken to reduce the sediment and improve fisheries include road upgrade, maintenance, and/or closure.  Road upgrades include installing larger culverts where needed, constructing rolling dips, and   removing diversion potential.

Planning and building new roads, as well as repairing and maintaining existing roads, are activities that require careful planning and implementation.  There are many factors involved in choosing where, when and how to build. 

This article has covered some key points among these issues; however, we urge you, whether you are a landowner planning some kind of development, a contractor or equipment operator implementing such projects, or an otherwise concerned citizen, to further educate yourself about responsible road building and maintenance techniques. 

The Trinity County RCD will soon be hosting a series of evening workshops that seek to provide you with more information.

The RCD will hold a series of free workshops in 2000 for landowners, contractors and equipment operators.  The workshops will focus on controlling erosion associated with road building and other grading practices. 

Erosion from construction sites is a source of sediment in our rivers and streams.  Much of it is preventable. Best management practices (BMP) can be used to reduce erosion from construction sites.  Preventing erosion helps protect our streams and local fisheries.  Participants, who successfully complete the workshop, will receive an Erosion Control BMP Manual and certificate of completion.  For more information please call us at 623-6004.  

These workshops are a cooperative effort with Trinity County, as a part of the Five-County Coho Plan, and are being funded though a grant from the U.S. Environmental Protection Agency.

Levels of sedimentation in the Trinity River and associated tributaries were judged by EPA and the North Coast Regional Water Quality Control Board (NCRWQCB) to exceed the existing Water Quality Standards necessary to protect the beneficial uses of the basin, particularly the cold water fishery.  Accelerated erosion from past and present land use practices and natural sources impacts the migration, spawning, reproduction, and early development of cold water fish such as spring and fall run Chinook salmon and steelhead trout. The mainstem and South Fork Trinity River watersheds are included on California’s Clean Water Act Section 303(d) list as water quality limited due to sediment.  This listing begins a process that leads to the adoption of allocations on the amount of sediment that can be put in the river and its tributaries, and to an implementation plan for meeting those limits. 

The EPA committed to develop total maximum daily loads (TMDLs) for 18 rivers in northern California by December 31, 2007 as a result of a lawsuit filed by the Pacific Coast Federation of Fisherman’s Associations.  The South Fork Trinity River TMDL was completed by EPA in December 1998.  TMDLs for other areas of the basin are scheduled for completion in 2001.  The purpose of these TMDLs is to identify sediment loading targets that, when implemented, are expected to result in meeting applicable water quality standards for sediment.

The components of the TMDLs include: Problem Statement-including assessment of instream and upslope conditions Instream Numeric Targets-intended to represent acceptable conditions for cold water fish Analysis of Significant Sediment Sources-past and present impacts on streams Linkage Analysis-to assess the magnitude of impairment and associated levels of sediment source reductions necessary to address the problem Allocation of Loads-to distribute needed load reductions among various sources

TMDLs are developed by reviewing and analyzing existing data on instream resources and desired conditions.  Implementation and meeting the targets of the TMDL is the responsibility of the NCRWQCB

The mainstem Trinity River watershed TMDL is in the planning stages. Data are currently being collected at many tributaries in the watershed in an effort to provide better insight into the sediment problems in the Trinity River. 

This information will help the EPA and local communities understand which tributaries have the most significant problems, and what sources of sediment could be controlled.  Studies elsewhere in northwestern California indicate that road networks, including private dirt roads and driveways, can be significant sources of sediment in streams.  Well designed and properly maintained roads pose much less of a problem.  The RCD will continue to monitor the development of the mainstem TMDL and will keep you informed of opportunities for community involvement.  You can also can get more information at EPA by calling Chris Heppe at (707) 825-2311 or http://www.epa.gov/docs/region09/water/tmdl/index.html.

Anadromous:  fish that are born and rear in fresh water,  mature at sea, and return to freshwater to reproduce.

Cross road drain: a deeply cut ditch, excavated across a road surface, which drains the road bed and inboard ditch.

Culvert: a transverse drain, usually a metal pipe, set beneath the road surface which drains water from the inside to the outside of the road.

Cutbank: the artificial face or slope cut into soils or rock along the inside of a road.

Diversion potential: a stream crossing has diversion potential if, when the culvert plugs, the stream would back up and flow down the road rather than over the crossing and back into the natural drainage.

Erosion: the dislodgement of soil particles caused by wind, raindrop impact, rilling, gullying, ravelling and other surface processes.

Grading: the act of excavating and moving soil along the road alignment to an established grade-line during road construction or pad preparation.

Runoff: rainfall or snowmelt which flows overland across the surface of hillslopes and along roads.

Sediment delivery: percent of material eroded from a site which actually gets delivered to a stream channel. 

Turbidity: refers to clarity of water measured by the extent to which light passing through water is reduced due to suspended materials, such as silt and clay.  Increasing turbidity is visually described as an increase in cloudiness.

In the design of forest and rural roads, it is important to take into consideration road surface drainage in order to maintain road stability and protect water quality.  There are certain guidelines that can be followed in road design and implementation which outline the most effective way to prevent or reduce sediment runoff and road failure due to drainage problems.  These guidelines are known as Best Management Practices, or BMP’s.  They are not a set of regulations that have been imposed by any agency, but rather a recommended set of standards which have been reached through consensus and experience by resource professionals in the relevant fields.

Here are some examples of Best Management Practices for sediment control on road construction and maintenance projects:

· Outsloping - creating an outward slope of the road surface helps to eliminate many of the problems with roads that collect water in an inboard ditch
· Rolling dips - also known as “rolling the grade,” this design feature helps ensure that surface runoff will not concentrate on the road surface and erode the roadbed; it also helps to disperse the runoff in lower concentrations at more points along the road
· Outlet protection - any point where water is discharged (from rolling dips, culverts, etc.) should be protected from eroding by rip rap, vegetation, or other adequate measures to dissipate the water’s energy
· Road surfacing - placement of some type of road surfacing, such as shale, is preferable to help prevent erosion of the road surface
· Clean fill material - fill material from cutbanks or other sources should be free of large organic debris, which can be a potential source of fillslope failure