03 road drainage

8/6/2019 03 Road Drainage

1/20

Road DrainageRoad Drainage


2/20

Road Drainage

Photo by Michael Brown


3/20

Interception of Subsurface Flow

(Adapted from Stone and Stone 1994)

Illustration courtesy of US Forest Service


4/20

Water Movement, Roads, andWatersheds

Photo Courtesy of US Forest Service


5/20


Roads affect the natural surface and

subsurface drainage pattern of a watershed

or individual hill slope. A basic objective of

road drainage design is to reduce the energy

generated by flowing water.


6/20

Select BMPs?

Protect storm drain inlets, manholes, and

watercourses before beginning work

Photo by Tyler Ledwith

Paved road BMPs are designed to

prevent sediment and road materials

from entering the stream system.

Sediment sources are usually from the

adjacent hill slope while chemical and

other pollutants wash into the streamsystem from the road surface.

Construction activities such as

Pothole Patching

Square Patching

Resurfacing

Paving

Crack Sealing

Overlay

Chip Sealing

can contribute pollutants to the stream

network.


7/20

Work Staging Areas


Staging areas for work sites should be set up to minimizesoil disturbance and the tracking of soil out of the work

area by vehicles and equipment.

In this case a good base of 3 aggregate

would be an appropriate BMP to minimize

mud tracking onto roadway.

Staging areas should be situated away from streamsand/or areas where runoff will be concentrated and

routed to the stream network.

Use the appropriate Erosion and Sediment Control BMPsto secure the staging area if there is soil disturbance.


8/20

The destructive

power of flowing

water increases

exponentially as itsvelocity increases.

Therefore,water must not be

allowed to developsufficient volume

or velocity so as to

cause excessive

wear along ditches,below culverts, or

along exposed

running surfaces,

cuts, or fills.Photo by Michael Brown


9/20



10/20

Erosion Control MeasuresClean Water!

In this case straw mulchis used to buffer rain

drops and minimize

erosion.

Silt Fence is used here tominimize sediment from

entering drainage ditch.

As with all BMPs

frequent monitoring is

necessary.

Sediment Control Measures


11/20

Paved Roads

Drainage ditch

away from

disturbed areas

Stabilized slopes with

shredded mulch.


12/20

Drainage ditch stabilized with erosion

control blankets to minimize erosion.

Erosion Control Blanket to

minimize erosion.Fiber roll

to control

sedimentdischarge

Sand bags

to direct

water


13/20

November 11, 2006November 11, 2006 Copyright 2005 Hossain KazemiCopyright 2005 Hossain Kazemi

Offsite drainage culvert stabilized with

erosion control measures.


14/20

The high-energy flow in

this drainage ditch is

carrying a significant

amount of sediment, but

the vegetation along the

sides of the channel is

keeping the channel

itself from eroding away

and causing moreproblems.


15/20

Check Dams are used to slow the rate of water to help

avoid overloading downhill culverts and drainage ditches.

They also reduce sediment flow.They should be heavy enough to withstand rapid water

flow but not so high or wide as to create damming orflooding of the road or erosion of the adjacent slope.

Some of the materials used for Check Dams include

large rock, gravel socks (like bags only longer) or gravelbags.

Fiber rolls are also used but need to be staked well.

Some have used fiber roll and covered with 4aggregate.

Spacing of the Check Dams will depend on pitch of the

grade.


16/20

Long Term BMPs for Ditches


Erosion blankets can

be used in steep

eroding ditches, but

must be replaced when

the blanket materialdeteriorates.

Rocking the ditch will

prevent erosion, but

will slow water

velocities and are not

recommended on highvolume shallow slopes.

Inboard ditches placed

on steep slopes and/or

erosive soils can erode

on a regular basis,

creating a constantsource of sediment to

the stream system.

Stabilizeditch with

BMP

techniques


17/20

Vegetated swales are a proven form of bio-

engineering for specific flow conditions.

Vegetated culverts promote a natural habitat

environment and are aesthetically pleasing.


18/20

Roadside Ditches

Ditches as Wetlands


Ditches with standing water can develop wetland characteristics,ultimately being classified as a protected area by state or Federal

agencies.

A biologist or other resource staff should be consulted before disturbingditches or other areas that have wetland vegetation or related aquatic

species.


19/20

Work in dry months

Vegetation cover isgood

Light touch

Leave vegetation onshoulder

In short


Unless a ditch is constantly

overflowing and threatening

public safety or a facility, a lighttouch, leaving existing

vegetation, may be the best

approach to ditch maintenance.


20/20

Road Drainage

Refer to FishNet Roads Manual BMP

Toolbox

Road Drainage BMPs

Rolling Dip

Outsloping

Ditch relief Culverts

Critical Dip Berm Removal

03 road drainage

Documents