By: Todd Thomas, Water Resources Forester, Texas A&M Forest Service
Q:
I have an old road that I use to access most of my property that is
fairly steep in some parts and has high banks on either side. The road itself has a good crown on it and
sheds water well. The problem lies with
the ditches. Due to the high banks I am
unable to install any turnouts to give the side ditches some relief until the
road reaches the bottom of the hill.
This makes for severely gutted out ditches. What can I do to keep my ditches from being
so washed out?
A: Excellent question. Believe it
or not, you are not alone in your problem.
This is especially common on roads that are retired county roads where
years of grading left the road severely below grade. Your issue is extremely problematic because
if left untreated the erosion occurring in your ditches will eventually begin
to undercut your road.
The best option that comes to mind that would be the most
long-lived would be the installation of small “Reno mattresses” in your
ditches. A Reno mattress is comprised of
chicken wire, stakes (ideally rebar), wire ties and rock or other
aggregate. These installations should
take up the full width of your ditch, be approximately one to two feet wide,
and one to two feet tall. The rock or
rip rap you use should be bigger around than that holes in the chicken
wire.
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| Small Reno mattress installations in side ditch on steep grade |
To install a Reno mattress, lay the chicken wire the
width of your ditch, dump your aggregate on top of the wire to form a mound one
to two feet wide and one to two feet tall, fold the wire over the top of your
rock mound and use wire to tie the chicken wire shut. Next, take your stakes and stake the Reno
mattress down on the front and on the back.
When installing the Reno mattresses take care to ensure that any flow
will not wash out the edges or undercut the installment. To determine the number and spacing you will
need, consult the Texas Forestry Best Management Practices Blue Book. The chart for waterbar spacing on page 54
should suffice, however if you think you need more, go for it. More of these will certainly not be
detrimental.
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| Top view of Reno mattress |
The functionality of these Reno mattresses is
twofold. The first function, as with all
BMPs is to slow down the flow. The
second function occurs from the slowed down flow; once the flow in the ditch is
slowed down any sediment it is carrying with it should settle out behind the
installment. Over time this should work
to fill in the ditch behind the mattress while allowing water to pass on
through. Sort of a “filtering”
effect.
