Water/Road Interaction Field Guide

Provide an illustrated field-going guide of observable water/road interaction problems damaging to road, watershed condition, water quality, aquatic life, or public safety;

Increase awareness of how road location, design, maintenance, and management affect interactions with rainfall, runoff, and ground water;

Facilitate communication on water/road interaction problems among professionals and technicians in a variety of physical and biological science disciplines and fields of engineering;

Improve recognition of basic road drainage problems, and the ability to identify and verify likely causes;

Increase awareness of possible alternative treatments to mitigate existing problems;

Develop knowledge and experience required to conceptualize road segment characteristics that provide desired safe access with minimal affect to watershed, water resources, and aquatic life;

Help inform line officer decisions.

Many drainage problems on low volume roads begin with surface water concentration and flow. Other problems involve road/stream crossings. Below are some contrasts, illustrated by the guide, between desirable conditions and those in which damage is occurring to road and/or watershed:

Desired: Roadway surfaces are sufficiently drained such that water flows do not concentrate volume or erosive energy levels causing access, safety, maintenance, or environmental problems;
Damaging: Roadway surfaces exhibit water concentration and erosion, with rills or gullys present over substantial areas. Wheel ruts present in the traveled way channel flow. The road prism is entrenched into the landscape;
Desired: Roadway surfaces are sufficiently treated such that concentrated flows do not leave the prism with volume or energy sufficient to cause gullys to adjacent areas or other mass erosion;
Damaging: Adjacent areas exhibit gullys that are not associated with the unroaded landscape condition. Sediment has been deposited in drainage ways and streams downslope of the road;
Desired: Road/stream crossings are designed to adequately duplicate naturally occuring conditions for passage of water, debris, bedload, and aquatic organisms, and do not exhibit diversion potential;
Damaging: Passage of one or more of the required entities is constricted, and diversion potential exists.

An electronic version of the draft Water/Road Interaction Field Guide is available on the San Dimas Technology and Development Center’s intranet web page. Navigate to Engineering, then Water/Road. The Field Guide link refers to a “work in progress.”

The Water/Road Interaction Field Guide is based on observable water/road interactions in ten major problem areas. These problem areas are:

Surface water concentration problems on the traveled way;
Surface water concentration problems on the backslope;
Surface water concentration problems on the fillslope;
Ditch or lead out ditch problems;
Subsurface flow interception by the prism;
Surface cross drain failure;
Ditch relief culvert failure;
Channel impacts/increased drainage density;
Channel encroachments from road alignment in channel/flood plain;
Road/Stream crossing problems.

Each of these ten problem areas contain multiple observations illustrated by photos. Each observation also provides:

Important site/road conditions;
Some possible treatments;
A reference/definition aid, and
A list of disciplines available to help recognize and analyze the problem.

Photos are captioned and show two scenarios: example observations of a water/road interaction problem on the ground, and situations in which the problem could occur, but does not, due to either nature or design. This is referred to in the Guide as Proper Drainage Provision.

Important road/site conditions are included with each observation as an aid to information gathering and to highlight critical conditions. The observer should consult with a specialist in the listed field for more information on critical conditions. Important site/road conditions are described as follows:

Geology—includes parent material characteristics, soil properties, and slope stability;
Climate—takes into consideration precipitation amounts, types, durations, intensities, and ambient temperatures;
Topography—includes landform type, shape, and relief;
Vegetation—involves types, characteristics, and ease of establishment;
Biology—includes plant, animal, and fish considerations as affected by road drainage and road drainage structures;
Template—refers to back and fillslope ratios and heights, traveled way surface shape and width, presence or absence of ditches and berms, and construction methods;
Grade—road grade;
Access—includes aspects of road location, road standards, maintenance, and vehicle considerations;
Policy—refers to any external constraints imposed on transportation system development and activities other than those described above.

Important site/road conditions are included to help the observer gather and organize information needed to recognize and analyze the problem. This list is not exhaustive: other conditions may apply and required information gathering needs can vary considerably. Possible treatments listed are basic configurations. Many other options and specialized treatments exist to aid solution of water/road interaction problems but are beyond the scope of this guide. The observer should consult with the specialist listed for more information on possible treatments. References (in italics) are mainly related to documents in the Water/Road Interaction Technology Series binder. Basic definitions and a listing of specialties for consultation are also provided. Specialties include hydrology, biology, geology, forestry, engineering, geotechnical engineering, maintenance, and include the Interdisciplinary Team in general.

Is	Is Not
A mentoring, training, and general design aid for professionals and technicians in physical and biological science and engineering disciplines	For specific design use by experienced professionals and technicians.
To facilitate use of the Water/Road Interaction Technology Series.	A stand-alone document that is comprehensive in and of itself.
As simple and concise as is reasonably possible.	An expert system.
A problem recognition and analysis tool.	A problem correction tool.
For leading from observations to most likely causes or basic problems.	For jumping from observation to treatment action.
For considering alternative treatments that could feasibly correct observed road drainage problems.	For prescribing a selected treatment.
For facilitating communication and conceptual understanding among personnel.	For selecting a specific course of action.
A field-going guide on low volume road drainage problems.	An office bound reference.
For use within the scope of typical authority of entry level professionals.	To encourage actions beyond typical authority or to bypass the decision making process.

Surface Water Concentration Problems on the Traveled Way
Loss of Surface Material

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Template
Grade
Access
Policy
Add surface cross drainage Engineer, Hydrologist The X-DRAIN Cross Drain Spacing and Sediment Yield Model, Cross Drain Update, Introduction to Surface Cross Drains

Modify template Engineer Traveled Way Surface Shape

Harden surface Engineer Pave, aggregate, vegetation, or chemical binder.

LOSS OF SURFACE MATERIALS PROPER DRAINAGE PROVISION

Surface water concentration and erosion on traveled way surface. Entrenchment of traveled way surface to 0.4 m below surrounding terrain due to use, erosion, and surface blading. Stable backslopes and fillslopes; well drained road surfaces. Grass on road surface prevents loss of surface materials.

Surface water concentration and erosion on traveled way surface. Entrenchment of traveled way surface to 0.4 m below surrounding terrain due to use, erosion, and surface blading. Stable backslopes and fillslopes; well drained road surfaces. Grass on road surface prevents loss of surface materials.

Gullying

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Template
Grade
Add surface cross drainage Engineer, Hydrologist The X-DRAIN Cross Drain Spacing and Sediment Yield Model, Cross Drain Update, Introduction to Surface Cross Drains

Modify template Engineer Traveled Way Surface Shape

Harden surface Engineer Pave, aggregate, or chemical binder.

Remedial maintenance Maintenance Foreman Remove gullies, maintain traveled way surface and other drainage provision to avoid gully erosion.

GULLYING PROPER DRAINAGE PROVISION

Gully formation on traveled way due to concentrated surface flow. 1 Stable backslopes and fillslopes; well drained road surfaces.

Gully formation on traveled way due to concentrated surface flow. Stable backslopes and fillslopes; well drained road surfaces.

Rutting

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Template
Access
Policy Add surface cross drainage Engineer Drain subgrade to ensure bearing capacity for wheel loads

Harden surface Engineer Pave or apply aggregate.

Remedial maintenance Maintenance Foreman Remove ruts; drain traveled way.

Manage traffic Interdisciplinary Team Seasonal closure; use restrictions.

Open canopy Biologist, Engineer, Forester Remove vegetation; increase drying of traveled surface.

RUTTING PROPER DRAINAGE PROVISION

Rutting of traveled way surface due to saturation and wheel loads. 1 Well drained outsloped road resists rutting.

Rutting of traveled way surface due to saturation and wheel loads. Well drained outsloped road resists rutting.

Sedimentation

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Climate
Topography
Vegetation
Biology
Template
Grade
Access Add surface cross drainage, isolate water concentrations Engineer, Hydrologist The X-DRAIN Cross Drain Spacing and Sediment Yield Model, Cross Drain Update, Introduction to Surface Cross Drains

Vegetative treatments, buffers Biologist, Forester, Range Conservationist Seeding, mulching, hydromulching, paper mulch, biotechnical treatments.

Remedial maintenance Maintenance Foreman Treat eroding surfaces and design drainage provision to avoid gully erosion.

SEDIMENTATION PROPER DRAINAGE PROVISION

Sedimentation on traveled way due to material eroded from higher on the road grade. Surface water concentration on road washes light cinder surfacing through lead out ditch to be deposited in meadow. Material deposited on traveled way, eroded from upslope on the road, and subsequently removed and piled here during maintenance operations. Grass on road prism prevents loss of surface materials.

Sedimentation on traveled way due to material eroded from higher on the road grade. Surface water concentration on road washes light cinder surfacing through lead out ditch to be deposited in meadow. Material deposited on traveled way, eroded from upslope on the road, and subsequently removed and piled here during maintenance operations. Grass on road prism prevents loss of surface materials.

Ponding

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Template
Grade
Access Add surface cross drainage Engineer Cross Drain Update

Modify template Engineer Traveled Way Surface Shape

PONDING PROPER DRAINAGE PROVISION

Ponding. Ponding on the traveled way. Stable backslopes and fillslopes, well drained road surfaces. Porous road fill prevents ponding problems on the traveled way.

Ponding. Ponding on the traveled way. Stable backslopes and fillslopes, well drained road surfaces. Porous road fill prevents ponding problems on the traveled way.

Berms

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Climate
Topography
Vegetation
Template
Access
Policy
Remove berm Engineer, Hydrologist Traveled Way Surface Shape

Excavate drainage path through berm Engineer, Hydrologist Outslope and provide drainage path or lead out ditch for surface flow over downhill shoulder.

Adjust snow removal practices Engineer, Hydrologist Ensure snow removal practices do not result in berms or surface water concentration on the road prism.

BERMS PROPER DRAINAGE PROVISION

Large berm increases distributed width of road and acts to keep water channeled on traveled way. Insloped traveled way with large berm on outside shoulder. Note the existence of rills running perpendicular to road center line even after surface blading. Berm left during snow plowing can lead to surface water concentration on the traveled way. Berm removal allows surface flow over downhill shoulder.

Large berm increases distributed width of road and acts to keep water channeled on traveled way. Insloped traveled way with large berm on outside shoulder. Note the existence of rills running perpendicular to road center line even after surface blading. Berm left during snow plowing can lead to surface water concentration on the traveled way. Berm removal allows surface flow over downhill shoulder.

Surface Water Concentration Problems on the Backslope
Erosion

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Template Vegetation, increase cover Biologist, Forester, Engr, Range Conservationist Seeding, mulch, hydromulch, papermulch, geosynthetic, biotechnical.

Modify slope Engineer Reduce slope, serrate, bench.

Harden surface Engineer Rock rip-rap, check dams.

Dispurse flow from above backslope Engineer, Hydrologist, Forester Ditch and/or berm.

EROSION PROPER DRAINAGE PROVISION

Backslope erosion and deposition of material on traveled way. Surface water concentration from above causing erosion of backslope: attempt to harden slope. Erosion susceptable backslope armored with rock rip-rap. Rolled hay bales placed at intervals on the backslope to reduce water concentrations and erosion.

Backslope erosion and deposition of material on traveled way. Surface water concentration from above causing erosion of backslope: attempt to harden slope. Erosion susceptable backslope armored with rock rip-rap. Rolled hay bales placed at intervals on the backslope to reduce water concentrations and erosion.

Slides on the Backslope

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Template
Access
Policy Modify slope, template Geotechnical Engineer Reduce slope, bench, retaining walls.

Modify weight distribution Geotechnical Engineer Rock buttress.

Bioengineering Engineer, Biologist Mechanical plus vegetative treatments.

SLIDES ON THE BACKSLOPE PROPER DRAINAGE PROVISION

Slumping backslope failure. Slumping failure on the backslope. Stable, well vegetated backslope. Rock filled gabion basket protection on backslope.

Slumping backslope failure. Slumping failure on the backslope. Stable, well vegetated backslope. Rock filled gabion basket protection on backslope.

Slides Extending Above Backslope

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Template
Access
Policy Consultation Geotechnical Specialist N/A

SLIDES EXTENDING ABOVE BACKSLOPE PROPER DRAINAGE PROVISION

Material above top of cut slope available for transport down to traveled way surface. Material deposited on traveled way from a slide extending above the top of cut. Hillslope above backslope sliding onto traveled way surface. Stable, well vegetated backslope.

Material above top of cut slope available for transport down to traveled way surface. Material deposited on traveled way from a slide extending above the top of cut. Hillslope above backslope sliding onto traveled way surface. Stable, well vegetated backslope.

Surface Water Concentration Problems on the Fillslope
Erosion

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Template
Grade Divert or disperse flow from upslope template, areas Engineer, Hydrologist Traveled Way Surface Shape, Introduction to Surface Cross Drains, the X-DRAIN Cross Drain Spacing and Sediment Yield Model

Establish vegetation Biologist, Forester, Range Conservationist Seed, mulch, plantings, biotechnical.

Armor surface Engineer Rock rip-rap, geosynthetics.

Adjust snow removal practices Engineer, Mtnc. Foreman Ensure practices do not lead to surface water concentrations.

Add over-side drains Engineer Drainage structure that protects fillslope from erosion. Caution: can increase erosive energy of water flow.

EROSION PROPER DRAINAGE PROVISION

Surface water concentration on fillslope from grade dip outflow. Erosion of fillslope due to concentrated surface flow. Rock rip-rap protection on the fillslope. Stable, well vegetated fillslope.

Surface water concentration on fillslope from grade dip outflow. Erosion of fillslope due to concentrated surface flow. Rock rip-rap protection on the fillslope. Stable, well vegetated fillslope.

Tension Cracks

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Template
Grade
Access
Policy Consultation Geotechnical Specialist N/A

TENSION CRACKS PROPER DRAINAGE PROVISION

Tension crack in traveled way due to excessive weight of saturated embankment. Tension cracks in asphalt surface due to embankment settlement. Well drained outslope road resists tension cracking.

Tension crack in traveled way due to excessive weight of saturated embankment. Tension cracks in asphalt surface due to embankment settlement. Well drained outslope road resists tension cracking.

Slides

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Template
Grade
Access
Policy
Consultation Geotechnical Specialist N/A

SLIDES PROPER DRAINAGE PROVISION

Over steepened fillslope slide. Grouted rock retaining wall to stabilize fillslope. Precast concrete log crib structure to stabilize fillslope.

Over steepened fillslope slide. Grouted rock retaining wall to stabilize fillslope. Precast concrete log crib structure to stabilize fillslope.

Ditch or Lead Out Ditch Problems
Erosion

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Template
Grade Increase ditch relief Engineer, Hydrologist, Biologist Relief Culverts

Decrease flow contribution from traveled way Engineer, Hydrologist Traveled Way Surface Shape

Decrease flow contribution from backslope Engineer, Hydrologist Vegetation, biotechnical, or mechanical treatments to backslope.

Vegetation Biologist, Range Conservationist Seed with grasses suitable for ditch.

Harden or armor flow area Engineer Line ditch with rock rip-rap or aggregate, or use in ditch culvert.

Modify ditch geometry Engineer Widen and flatten flow path if possible, or add energy dissipators.

EROSION PROPER DRAINAGE PROVISION

Erosion and downcutting of inboard ditch.-a Ditch pavement to resist erosion and subsequent sedimentation. Grouted rock lead out ditch resists erosion.

Erosion and downcutting of inboard ditch. Ditch pavement to resist erosion and subsequent sedimentation. Grouted rock lead out ditch resists erosion.

Sedimentation

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Biology
Template
Grade
Access
Policy Reduce upslope erosion Engineer, Hydrologist, Biologist Harden, vegetate upslope area.

Decrease flow contribution from traveled way Engineer, Hydrologist Traveled Way Surface Shape

Decrease flow contribution from backslope Engineer, Hydrologist Vegetation, geosynthetic or organic mat, structural treatments.

Modify ditch geometry, relief Engineer, Hydrologist Steepen flow path if possible.

SEDIMENTATION PROPER DRAINAGE PROVISION

Clogging of ditch with sediment from upslope road segment. Deposition, clogging of lead out ditch with light cinder surfacing washed from traveled way. Properly functioning lead out ditch. Well vegetated ditch reduces downstream sedimentation.

Clogging of ditch with sediment from upslope road segment. Deposition, clogging of lead out ditch with light cinder surfacing washed from traveled way. Properly functioning lead out ditch. Well vegetated ditch reduces downstream sedimentation.

Backslope Undermining

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Template
Grade
Policy Harden ditch, in-ditch culvert Engineer Pave, line with rock, vegetate. In-ditch culvert prevents downcutting.

Modify ditch geometry Engineer Flatten flow path if possible.

BACKSLOPE UNDERMINING PROPER DRAINAGE PROVISION

Undermining of backslope due to downcutting of ditch. Paved ditch resists erosion and downcutting. Well vegetated ditch reduces backslope undermining.

Undermining of backslope due to downcutting of ditch. Paved ditch resists erosion and downcutting. Well vegetated ditch reduces backslope undermining.

Subsurface Flow Interception by the Prism
Prism Saturation

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Template
Access
Policy Direct flow underneath road surface in french drain Engineer, Hydrologist French drain, aggregate, and geotextile or geocomposite.

Direct flow underneath road surface in porous fill Engineer, Hydrologist Large, uniformly graded rocky fill with riding surface cap.

Seal or harden riding surface Engineer Pavement, aggregate.

Install low water crossing Engineer, Hydrologist Subgrade designed to support wheel loads and survive overtopping flows.

PRISM SATURATION PROPER DRAINAGE PROVISION

Backslope seepage causing saturated road subgrade. - a View of porous fill built over area saturated by exfiltration of subsurface flow. Porous fill prevents prism saturation problems due to intercepted subsurface flow.

Backslope seepage causing saturated road subgrade. View of porous fill built over area saturated by exfiltration of subsurface flow. Porous fill prevents prism saturation problems due to intercepted subsurface flow.

Erosion/Rutting

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Template
Grade
Access
Policy Direct flow underneath road surface in french drain Engineer, Hydrologist French drain, aggregate, and geotextile or geocomposite.

Direct flow underneath road surface in porous fill Engineer, Hydrologist Large, uniformly graded rocky fill with riding surface cap.

Harden riding surface Engineer Pavement, aggregate.

Install low water crossing Engineer, Hydrologist Traveled way designed for overtopping flows.

EROSION/RUTTING PROPER DRAINAGE PROVISION

Erosion and rutting potential due to subsurface flow interception by the prism. Porous fill provides hardened riding surface to resist erosion and rutting.

Erosion and rutting potential due to subsurface flow interception by the prism. Porous fill provides hardened riding surface to resist erosion and rutting.

Ponding

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Climate
Topography
Template
Grade
Access
Policy Direct flow underneath road surface in french drain Engineer, Hydrologist French drain, aggregate, and geotextile or geocomposite.

Direct flow underneath road surface in permeable fill Engineer, Hydrologist Large, uniformly graded rocky fill with riding surface cap.

Install low water crossing Engineer, Hydrologist Traveled way designed for overtopping flows.

Modify template Engineer Traveled Way Surface Shape

PONDING PROPER DRAINAGE PROVISION

Ponding problems due to subsurface flow interception by the prism. Ponding problem on traveled way due to intercepted subsurface flow. Built-up porous fill relieves ponding problems by providing drainage in areas exhibiting exfiltration of subsurface flow.

Ponding problems due to subsurface flow interception by the prism. Ponding problem on traveled way due to intercepted subsurface flow. Built-up porous fill relieves ponding problems by providing drainage in areas exhibiting exfiltration of subsurface flow.

Surface Cross Drain Failure
Erosion of Cross Drain

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Template
Grade
Access Add surface cross drainage Engineer, Hydrologist The X-DRAIN Cross Drain Spacing and Sediment Yield Model, Cross Drain Update, Introduction to Surface Cross Drains

Minimize contributing drainage areas Engineer, Hydrologist Reduce area contributing surface flow with vegetation, organic material, or geosynthetics.

Isolate contributing drainage areas Engineer, Geologist Keep surface flows from individual contributing areas from accumulating.

Clean/maintain/restore cross drain Maintenance Foreman Restore cross drain function.

Harden drain area Engineer Provide erosion proof or resistant flow path.

Vegetation Biologist, Forester, Range Conservationist Seed, mulch, or plantings.

EROSION OF CROSS DRAIN PROPER DRAINAGE PROVISION

Erosion of grade dip. - a Erosion of grade dip. - b Grouted rock lead out ditch resists erosion. Uniformly graded rock used to armor cross drain.

Erosion of grade dip. Grouted rock lead out ditch resists erosion. Uniformly graded rock used to armor cross drain.

Deposition

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Template
Grade
Access Add surface cross drainage Engineer, Hydrologist The X-DRAIN Cross Drain Spacing and Sediment Yield Model, Cross Drain Update, Introduction to Surface Cross Drains

Clean/maintain/restore cross drain Maintenance Foreman Restore cross drain function.

Harden/armor upslope surface Engineer, Geologist Reduce erosion from upslope areas to reduce downstream deposition.

DEPOSITION PROPER DRAINAGE PROVISION

Filling in of grade dip outflow with sediment. Deposition of light cinder road surfacing in meadow and clogging of lead out ditch. Hardened upslope surface resists erosion, allowing this grade dip outflow to remain free flowing.

Filling in of grade dip outflow with sediment. Deposition of light cinder road surfacing in meadow and clogging of lead out ditch. Hardened upslope surface resists erosion, allowing this grade dip outflow to remain free flowing.

Bypassed Structure

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Template
Grade
Access Add surface cross drainage Engineer, Hydrologist The X-DRAIN Cross Drain Spacing and Sediment Yield Model, Cross Drain Update, Introduction to Surface Cross Drains

Deepen drainage structure (consult engineer) Engineer Ensure flow paths are directed into cross drain.

BYPASSED STRUCTURE PROPER DRAINAGE PROVISION

Bypassing of cross drain outflow due to deposition of sediment. Bypassed lead out ditch due to insloped traveled way surface shape. Lack of bypass problems on lead out ditch.

Bypassing of cross drain outflow due to deposition of sediment. Bypassed lead out ditch due to insloped traveled way surface shape. Lack of bypass problems on lead out ditch.

Ditch Relief Culvert Failure
Inlet Plugging

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Template
Grade
Access Remove inlet obstructions Maintenance Foreman Clean inlet, trash rack, or sedimentation pond.

Vegetate upslope area Biologist, Forester, Range Conservationist Seed or plant upslope area to reduce erosion.

Diversion prevention dip Engineer, Hydrologist Diversion Potential at Road/Stream Crossings

Maintain/clean ditch Maintenance Foreman Remove materials threatening inlet plugging.

Gully treatments Engineer, Hydrologist, Geologist Gully plugs or harden ditch.

Entrance treatments Engineer Enhance passage of debris.

INLET PLUGGING PROPER DRAINAGE PROVISION

Ditch relief culvert subject to sediment plugging. Ditch relief culvert on the verge of plugging due to sedimentation in inlet basin. Cast in place concrete catch basin creates swirling action that flushes organic debris and sediment through cross drain culvert. Ditch relief culvert inlet plugging prevented by concrete “L” shaped structure.

Ditch relief culvert subject to sediment plugging. Ditch relief culvert on the verge of plugging due to sedimentation in inlet basin. Cast in place concrete catch basin creates swirling action that flushes organic debris and sediment through cross drain culvert. Ditch relief culvert inlet plugging prevented by concrete “L” shaped structure.

Inlet Bypassing

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Template
Grade
Access Ditch dam Engineer, Hydrologist Dam ditch to direct flow into culvert.

Maintain/clean ditch Maintenance Foreman Remove materials threatening inlet plugging and subsequent bypassing.

Modify template Engineer Ensure template directs flow into culvert.

Diversion prevention dip Engineer, Hydrologist Diversion Potential at Road/Stream Crossings

INLET BYPASSING PROPER DRAINAGE PROVISION

Ditch erosion downstream of bypassed ditch relief culvert inlet. Bypassed cross drain culvert due to complete burial under sediment. Cast in place concrete catch basin functions as a ditch dam to prevent inlet bypassing. Ditch relief culvert inlet bypassing prevented by concrete “L” shaped structure.

Ditch erosion downstream of bypassed ditch relief culvert inlet. Bypassed cross drain culvert due to complete burial under sediment. Cast in place concrete catch basin functions as a ditch dam to prevent inlet bypassing. Ditch relief culvert inlet bypassing prevented by concrete “L” shaped structure.

Corroded or Damaged Pipe

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Policy Replace/realign/move culvert (consult engineer) Engineer Grout or pave corroded invert; repair or replace pipe damaged by maintenance operations.

CORRODED OR DAMAGED PIPE PROPER DRAINAGE PROVISION

Cross drain pipe inlet dented during maintenance operation contributes to deposition in inlet basin. Ditch relief culvert failure due to crushed pipe inlet. Concrete cross drain pipe resists corrosion and damage.

Cross drain pipe inlet dented during maintenance operation contributes to deposition in inlet basin. Ditch relief culvert failure due to crushed pipe inlet. Concrete cross drain pipe resists corrosion and damage.

Instability Below Outlet

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Template Replace/realign/move culvert Engineer Consult Engineer.

Construct retaining wall Geotechnical Engineer Prop unstable slope.

Outlet downspout Engineer, Hydrologist Protect unstable area.

INSTABILITY BELOW THE OUTLET PROPER DRAINAGE PROVISION

Ditch relief culvert outlet “shotgunned” due to fillslope erosion and instability. - a Rock retaining wall to increase stability of fill over ditch relief culvert. Member of a set of closely spaced ditch relief culverts minimizes affects to surroundings.

Ditch relief culvert outlet “shotgunned” due to fillslope erosion and instability. Rock retaining wall to increase stability of fill over ditch relief culvert. Member of a set of closely spaced ditch relief culverts minimizes affects to surroundings.

Outlet Scour

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation Harden outfall Engineer Rock rip-rap or outlet downspout to protect receiving area.

Add ditch relief Engineer, Hydrologist Reduce flow onto unstable area.

Replace/realign/move culvert (consult engineer) Engineer Move pipe so outflow is onto stable area.

OUTLET SCOUR PROPER DRAINAGE PROVISION

Scour at ditch relief culvert outlet. Dry laid rock masonry with sill built by CCC reduces outlet scour. Member of a set of closely spaced ditch relief culverts minimizes affects to surroundings. - a

Scour at ditch relief culvert outlet. Dry laid rock masonry with sill built by CCC reduces outlet scour. Member of a set of closely spaced ditch relief culverts minimizes affects to surroundings.

Inadequate Pipe Cover

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Template
Access Ramp over pipe Engineer, Hydrologist Place additional material over pipe installation.

Reduce loss of fines/erosion over pipe Maintenance Foreman Properly maintain roadbed to reduce erosion.

INADEQUATE PIPE COVER PROPER DRAINAGE PROVISION

Inadequate cover over pipe. Inadequate cover over corrugated metal pipe approximately 0.15m (6 in) deep where 0.3m (12 in) is required. Ample cover on ditch relief culvert.

Inadequate cover over pipe. Inadequate cover over corrugated metal pipe approximately 0.15m (6 in) deep where 0.3m (12 in) is required. Inadequate cover over pipe. Ample cover on ditch relief culvert.

Channel Impacts/Increased Drainage Density
Erosion

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Biology
Template
Grade
Access Slow and disperse water flows Engineer, Hydrologist Traveled Way Surface Shape, The X-DRAIN Cross-Drain Spacing and Sediment Yield Model, Introduction to Surface Cross Drains

Vegetation Biologist, Forester, Range Conservationist Vegetate eroding areas.

Gully Treatments Engineer, Hydrologist, Geologist Use vegetative and/or mechanical treatments to reduce gully erosion.

Diversion prevention dip Engineer, Hydrologist Diversion Potential at Road-Stream Crossings

Reduce contributing area Engineer, Hydrologist Traveled Way Surface Shape, The X-DRAIN Cross-Drain Spacing and Sediment Yield Model, Introduction to Surface Cross Drains

EROSION PROPER DRAINAGE PROVISION

Gully erosion resulting in increased drainage density due to excess surface water concentration from traveled way. Elevated CMP inlet/elbow encourages ponding, deposition, and soil moisture recharge, while buffering downstream flows and reducing erosion. Successful seeding and revegetation reduces erosion and channel development upstream of a road drainage structure.

Gully erosion resulting in increased drainage density due to excess surface water concentration from traveled way. Elevated CMP inlet/elbow encourages ponding, deposition, and soil moisture recharge, while buffering downstream flows and reducing erosion. Successful seeding and revegetation reduces erosion and channel development upstream of a road drainage structure.

Sedimentation

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Biology
Template
Grade
Access
Policy Vegetation Biologist, Forester, Range Conservationist Use vegetation to reduce sediment transport.

Gully treatments Engineer, Hydrologist, Geologist Use gully plugs to increase deposition in desired locations.

Sedimentation ponds Engineer, Hydrologist, Biologist Use sedimentation ponds to increase deposition in desired locations.

SEDIMENTATION PROPER DRAINAGE PROVISION

Deposition upstream of road stream crossing due to inadequate pipe capacity. Channel bottom clogged with light cinder surfacing from road. Sedimentation pond causes deposition in desired location and protects downstream areas.

Deposition upstream of road stream crossing due to inadequate pipe capacity. Channel bottom clogged with light cinder surfacing from road. Sedimentation pond causes deposition in desired location and protects downstream areas.

Hydrologic Connectivity

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Biology
Template Slow and disperse water flows Engineer, Hydrologist Traveled Way Surface Shape, The X-DRAIN Cross-Drain Spacing and Sediment Yield Model, Introduction to Surface Cross Drains

Vegetation Biologist, Forester, Range Conservationist Use vegetation to slow flows and stabilize soil.

Desynchronize flows Engineer, Hydrologist Traveled Way Surface Shape, The X-DRAIN Cross-Drain Spacing and Sediment Yield Model, Introduction to Surface Cross Drains

Reduce contributing area Engineer, Hydrologist Traveled Way Surface Shape, The X-DRAIN Cross-Drain Spacing and Sediment Yield Model, Introduction to Surface Cross Drains

Gully treatments Engineer, Hydrologist Treat gullies with plugs, vegetation, biotechnical, mechanical methods.

HYDROLOGIC CONNECTIVITY PROPER DRAINAGE PROVISION

Hydrologic connectivity between road and stream due to surface water concentration and flow off road. Gullying in area adjacent to road due to hydrologic connectivity successfully treated, with area healing. - a

Hydrologic connectivity between road and stream due to surface water concentration and flow off road. Gullying in area adjacent to road due to hydrologic connectivity successfully treated, with area healing.

Reduced Moisture

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Biology
Template
Grade
Access Slow and disperse water flows Engineer, Hydrologist Traveled Way Surface Shape, The X-DRAIN Cross-Drain Spacing and Sediment Yield Model, Introduction to Surface Cross Drains

Vegetation Biologist, Forester, Range Conservationist Use of vegetation to increase soil moisture recharge.

Retain moisture on site Engineer, Hydrologist Perform treatments to reduce loss of moisture from site.

REDUCED MOISTURE PROPER DRAINAGE PROVISION

Site drying and groundwater table lowered due to gullies caused by pipes installed below meadow elevation. Proper drainage provision built and maintained into road encourages ponding and recharge of soil moisture.

Site drying and groundwater table lowered due to gullies caused by pipes installed below meadow elevation. Proper drainage provision built and maintained into road encourages ponding and recharge of soil moisture.

Channel Encroachment From Road Alignment in Channel/Flood Plain
Loss of Road Prism

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Biology
Template
Grade
Access
Policy Realign road Inter-disciplinary Team Move road away from stream.

Install retaining structure Geotechnical Engineer Retain and protect fill from erosion.

Harden fillslope Engineer Protect fill from washout.

Realign stream Inter-disciplinary Team Move stream away from road.

Barbs/revetments (consultation) Engineer, Hydrologist, Biologist Reduce erosion, encourage deposition.

LOSS OF ROAD PRISM PROPER DRAINAGE PROVISION

Erosion of the fillslope due to channel encroachment by the road prism. Erosion of road prism from channel encroachment. Fillslope retaining wall prevents channel encroachment. Bank barbs placed in channel prevent erosion and encourage deposition, protecting the road prism.

Erosion of the fillslope due to channel encroachment by the road prism. Erosion of road prism from channel encroachment. Fillslope retaining wall prevents channel encroachment. Bank barbs placed in channel prevent erosion and encourage deposition, protecting the road prism.

Channel Erosion

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Biology Realign road Inter-disciplinary Team Move road away from stream.

Protect channel banks (bioengineering) Engineer, Hydrologist, Biologist Vegetative and structural protection.

In-channel structure Engineer, Hydrologist Reduce erosion, encourage deposition.

CHANNEL EROSION PROPER DRAINAGE PROVISION

Channel erosion downstream of road/stream crossing structure. Channel bank erosion worsened by road prism encroachment in channel. Sufficient buffer between road and stream to prevent impacts to stream and fish habitat.

Channel erosion downstream of road/stream crossing structure. Channel bank erosion worsened by road prism encroachment in channel. Sufficient buffer between road and stream to prevent impacts to stream and fish habitat.

Sedimentation

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Biology Consult Biologist Biologist, Hydrologist N/A

Barbs/revetments (consultation) Engineer, Biologist Encourage deposition in desired areas.

SEDIMENTATION PROPER DRAINAGE PROVISION

Material eroded from top of fill ends up in stream and degrades fish habitat. Deposition of light cinder surfacing in channel downslope of road alignment encroaching in channel. Sufficient buffer between road and stream to prevent impacts to stream and fish habitat.

Material eroded from top of fill ends up in stream and degrades fish habitat. Deposition of light cinder surfacing in channel downslope of road alignment encroaching in channel. Sufficient buffer between road and stream to prevent impacts to stream and fish habitat.

Channel Encroachment

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Biology
Access
Policy Realign road Inter-disciplinary Team Move road away from stream.

Realign stream Inter-disciplinary Team Move stream away from road.

CHANNEL ENCROACHMENT PROPER DRAINAGE PROVISION

Channel encroachment by road prism fillslope. - a Sufficient buffer between road and stream to prevent impacts to stream and fish habitat.

Channel encroachment by road prism fillslope. Sufficient buffer between road and stream to prevent impacts to stream and fish habitat.

Over Steepend Stream Channels

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Biology
Access
Policy Realign road Inter-disciplinary Team Move road away from stream.

Realign stream Inter-disciplinary Team Move stream away from road.

Barbs/revetments (consultation) Engineer, Hydrologist, Biologist, Geologist Reduce erosion, encourage deposition.

In channel structure Engineer, Hydrologist, Biologist Reduce erosion, encourage deposition.

OVER STEEPENED STREAM CHANNELS PROPER DRAINAGE PROVISION

Stream channel steepened, straightened, and shortened due to channel encroaching fill. Sufficient buffer between road and stream to prevent impacts to stream and fish habitat.

Stream channel steepened, straightened, and shortened due to channel encroaching fill. Sufficient buffer between road and stream to prevent impacts to stream and fish habitat.

Isolation of Flood Plain From Stream

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Climate
Topography
Biology
Access
Policy Realign road Inter-disciplinary Team Move road out of flood plain.

Realign stream Inter-disciplinary Team Move stream away from road.

ISOLATION OF FLOOD PLAIN FROM STREAM PROPER DRAINAGE PROVISION

View looking away from road at flood plain isolated by turnpike road prism. Turnpike road fill causing isolation of flood plain. Sufficient buffer between road and stream to prevent impacts to stream and fish habitat.

View looking away from road at flood plain isolated by turnpike road prism. Turnpike road fill causing isolation of flood plain. Sufficient buffer between road and stream to prevent impacts to stream and fish habitat.

Road/Stream Crossing Problems
Inlet Plugging

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Vegetation
Biology Remove organic debris Maintenance Foreman Clean channel and upslope areas of debris.

Shape, maintain, clean entrance Maintenance Foreman, Engineer Unplug inlet, shape entrance to optimize drainage.

Trash rack, debris rack Engineer Install rack to prevent plugging of inlet by debris.

Stand pipe w/drop inlet Engineer, Hydrologist, Biologist Stand pipe with drop inlet provides overflow protection in case structure inlet becomes plugged with debris.

INLET PLUGGING PROPER DRAINAGE PROVISION

Road stream crossing culverts plugged with debris, leading to scour of the fillslope. Inlet is partially plugged by rock and is dented by maintenance equipment. Stand pipe with drop inlet overflow protection in debris laden stream. Removable grid on cast in place culvert provides easy cleaning of debris from drainage crossing structure.

Road stream crossing culverts plugged with debris, leading to scour of the fillslope. Inlet is partially plugged by rock and is dented by maintenance equipment. Stand pipe with drop inlet overflow protection in debris laden stream. Removable grid on cast in place culvert provides easy cleaning of debris from drainage crossing structure.

Enlarged Inlet Basin

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Biology
Template
Policy Shape/maintain/clean basin Maintenance Foreman Ensure basin geometry provides for passage of debris through structure.

Entrance treatment Engineer Flared inlet enhances passage of debris.

Trash or debris rack Engineer Trash or debris rack keeps debris from plugging inlet.

Add drainage structure Engineer Added drainage structure provides overflow in case inlet becomes plugged.

Stand pipe with drop inlet Engineer Stand pipe with drop inlet provides overflow in case inlet becomes plugged.

ENLARGED INLET BASIN PROPER DRAINAGE PROVISION

Large, open inlet basin encourages blockage of pipe inlet with debris. Tapered inlet basin enhances passage of bedload and woody debris.

Stream Diversion

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Biology
Template
Grade
Access Diversion prevention dip Hydrologist, Engineer Diversion Potential at Road-Stream Crossings

STREAM DIVERSION PROPER DRAINAGE PROVISION

Potential stream diversion out of natural channel due to plugging and dented inlet. Absence of stream diversion potential at road stream crossing drainage structure.

Potential stream diversion out of natural channel due to plugging and dented inlet. Absence of stream diversion potential at road stream crossing drainage structure. Construction of a dip to intercept overtopping flows and prevent diversion down the road or ditchline. This sketch depicts a diversion prevention dip on a low volume, low speed, single-lane road. The dip should intercept any ditchline present, and be of sufficient capacity to handle the entire expected design peakflow. Special care should be exercised in constructing the beginning (upslope end) of the dip where the rediversion of streamflow back toward the channel must occur and persist.

Culvert Washout

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Topography
Biology
Template Harden Crossing Engineer, Hydrologist Provide erosion resistance to road stream crossing.

Increase flow capacity Engineer, Hydrologist Replace culvert with structure having greater capacity, add culvert, or install an entrance treatment to increase capacity.

CULVERT WASHOUT PROPER DRAINAGE PROVISION

Road stream crossing culvert washout due to insufficient capacity. Vented low water crossing with concrete pipe and fillslopes. Road/stream crossing fillslope armored with rip-rap to resist culvert washout.

Road stream crossing culvert washout due to insufficient capacity. Road stream crossing culvert washout due to lack of capacity. Vented low water crossing with concrete pipe and fillslopes. Road/stream crossing fillslope armored with rip-rap to resist culvert washout.

Culvert Piping

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Biology
Template Entrance treatment Engineer, Hydrologist Flared inlet can reduce or eliminate piping.

Rebed pipe Engineer Remove and reinstall pipe using proper bedding materials and procedures.

CULVERT PIPING PROPER DRAINAGE PROVISION

Streamflow piping around culvert can lead to embankment failure. Properly bedded pipe prevents piping.

Streamflow piping around culvert can lead to embankment failure. Properly bedded pipe prevents piping.

Corrosion/Drainage of Structure

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Biology
Template Replace pipe Engineer Remove damaged structure and install appropriate replacement.

Repair pipe Engineer Use cement grout or insert to extend life of damaged structure.

CORRODED OR DAMAGED STRUCTURES PROPER DRAINAGE PROVISION

Rusted pipe inverts cause piping and undermining of structure. Cemented grout repair of abraded and corroded CMP invert.

Rusted pipe inverts cause piping and undermining of structure. Cemented grout repair of abraded and corroded CMP invert.

Excessive Outlet Falls

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Biology Gully treatments Hydrologist, Engineer, Biologist, Geologist Install gully plugs or other treatments to prevent downcutting and encourage deposition.

EXCESSIVE OUTLET FALLS PROPER DRAINAGE PROVISION

Channel erosion downstream of road/stream crossing structure. - a Outlet half pipe to protect fillslope from erosion. Caution: this treatment can accelerate flow and increase downsteam erosion potential. Ponded condition at road stream crossing drainage structure outlet reduces erosion potential.

Channel erosion downstream of road/stream crossing structure. Outlet half pipe to protect fillslope from erosion. Caution: this treatment can accelerate flow and increase downsteam erosion potential. Ponded condition at road stream crossing drainage structure outlet reduces erosion potential.

Outlet Fillslope Erosion

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Geology
Climate
Topography
Vegetation
Biology Harden fillslope Engineer Gabions, cribs, retaining walls, concrete, pavement, or drainage structure extension.

Rebed pipe Engineer Remove and reinstall pipe at proper elevation using proper bedding materials and procedures.

Gully treatments Engineer, Hydrologist, Biologist, Geologist Install gully plugs or other treatments to prevent downcutting and encourage deposition.

OUTLET FILLSLOPE EROSION PROPER DRAINAGE PROVISION

Low water crossing with scour and erosion of downstream side. Outlet half pipe to protect fillslope from erosion. Caution: this treatment can accelerate flow and increase downstream erosion potential. Road stream crossing culvert extending down fillslope to prevent erosion. Caution: this treatment can accelerate flow and increase downstream erosion potential.

Low water crossing with scour and erosion of downstream side. Outlet half pipe to protect fillslope from erosion. Caution: this treatment can accelerate flow and increase downstream erosion potential. Road stream crossing culvert extending down fillslope to prevent erosion. Caution: this treatment can accelerate flow and increase downstream erosion potential.

Fish Passage Barriers

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Climate
Topography
Biology Rebed or replace pipe Engineer, Biologist Remove and reinstall pipe using proper bedding materials and procedures at proper inlet and outlet elevations.

Install fish passage structures Engineer, Biologist Baffles or fish ladders.

FISH PASSAGE BARRIERS PROPER DRAINAGE PROVISION

Water velocity causes road-stream crossing drainage structure to act as an aquatic species passage barrier. Channel erosion downstream of road/stream crossing structure presents barrier to aquatic species passage. Fish ladder. Baffles in road stream crossing drainage structure encourage fish passage.

Water velocity causes road-stream crossing drainage structure to act as an aquatic species passage barrier. Channel erosion downstream of road/stream crossing structure presents barrier to aquatic species passage. Fish ladder. Baffles in road stream crossing drainage structure encourage fish passage.

Inadequate Capacity

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Climate
Template Add drainage structure Engineer Increase flow capacity of crossing by additional structure.

Resize pipe Engineer Replace structure with larger capacity structure.

Entrance treatment Engineer Increase capacity by installing flared inlet.

INADEQUATE CAPACITY PROPER DRAINAGE PROVISION

Deposition upstream of road stream crossing due to inadequate pipe capacity. Road/stream crossing drainage structure increasing velocity of stream flow. Road stream crossing drainage structure sized to pass 100-year flow. Drainage structures (2-24 inch CMP) added to increase crossing capacity.

Deposition upstream of road stream crossing due to inadequate pipe capacity. Road/stream crossing drainage structure increasing velocity of stream flow. Road stream crossing drainage structure sized to pass 100-year flow. Drainage structures (2-24 inch CMP) added to increase crossing capacity.

Improper Alignment

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Climate
Topography
Biology
Template
Grade Realign pipe Hydrologist, Engineer Remove and reinstall pipe at proper alignment.

IMPROPER ALIGNMENT PROPER DRAINAGE PROVISION

Improper alignment of road stream crossing CMP lead to debris blockage problems. - a

Improper alignment of road stream crossing CMP lead to debris blockage problems. Proper alignment of road stream crossing drainage structure.

Inlet Fillslope Erosion

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Template
Grade
Access Fillslope treatments Engineer Install gabions, cribs, retaining walls, to reduce or eliminate fillslope erosion.

INLET FILLSLOPE EROSION PROPER DRAINAGE PROVISION

Erosion of fillslope. Rock filled gabion inlet fillslope protection.

Erosion of fillslope. Rock filled gabion inlet fillslope protection.

Increased Hydraulic Energy

Important Site/Road Conditions Possible Treatments Specialist Reference/Definition

Climate
Topography
Biology
Template Slow and disperse water flows Engineer, Hydrologist Traveled Way Surface Shape, The X-DRAIN Cross Drain Spacing and Sediment Yield Model, Introduction to Surface Cross Drains

Vegetation Biologist, Forester, Range Conservationist Use vegetation to slow flows.

Desynchronize flows Engineer, Hydrologist Traveled Way Surface Shape, The X-DRAIN Cross Drain Spacing and Sediment Yield Model, Introduction to Surface Cross Drains

Reduce contributing area Engineer, Hydrologist Traveled Way Surface Shape, The X-DRAIN Cross Drain Spacing and Sediment Yield Model, Introduction to Surface Cross Drains

INCREASED HYDRAULIC ENERGY PROPER DRAINAGE PROVISION

Road/stream crossing drainage structure increasing velocity of stream flow. Elevated CMP inlet ponds water and reduces hydraulic energy of flows.

Road/stream crossing drainage structure increasing velocity of stream flow. Elevated CMP inlet ponds water and reduces hydraulic energy of flows. Successful seeding and revegetation of eroded area downstream of a road drainage structure reduces hydraulic energy of flows.

For Additional Information Contact:
Transportation Program Leader
San Dimas Technology & Development Center
444 East Bonita Avenue, San Dimas CA 91773-3198
Phone 909-599-1267; TDD: 909-599-2357; FAX: 909-592-2309
E-mail: mailroom_wo_sdtdc@fs.fed.us

Information contained in this document has been developed for the guidance of employees of the Forest Service, United States Department of Agriculture (USDA), its contractors, and cooperating Federal and State agencies. The USDA assumes no responsibility for the interpretation or use of this information by other than its own employees. The use of trade, firm, or corporation names is for the information and convenience of the reader. Such use does not constitute an official evaluation, conclusion, recommendation, endorsement, or approval of any product or service to the exclusion of others that may be suitable.

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, sex, religion, age, disability, political beliefs, sexual orientation, or marital or family status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD).

To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326-W, Whitten Building, 1400 Independence Avenue, SW, Washington, D.C. 20250-9410 or call (202) 720-5964 (voice and TDD). USDA is an equal opportunity provider and employer.

Important Site/Road Conditions	Possible Treatments	Specialist	Reference/Definition
Geology Climate Template Grade Access Policy	Add surface cross drainage	Engineer, Hydrologist	The X-DRAIN Cross Drain Spacing and Sediment Yield Model, Cross Drain Update, Introduction to Surface Cross Drains
	Modify template	Engineer	Traveled Way Surface Shape
	Harden surface	Engineer	Pave, aggregate, vegetation, or chemical binder.

LOSS OF SURFACE MATERIALS		PROPER DRAINAGE PROVISION

Surface water concentration and erosion on traveled way surface.	Entrenchment of traveled way surface to 0.4 m below surrounding terrain due to use, erosion, and surface blading.	Stable backslopes and fillslopes; well drained road surfaces.	Grass on road surface prevents loss of surface materials.

GULLYING				PROPER DRAINAGE PROVISION

Gully formation on traveled way due to concentrated surface flow.				Stable backslopes and fillslopes; well drained road surfaces.

RUTTING			PROPER DRAINAGE PROVISION

Rutting of traveled way surface due to saturation and wheel loads.			Well drained outsloped road resists rutting.

SEDIMENTATION			PROPER DRAINAGE PROVISION

Sedimentation on traveled way due to material eroded from higher on the road grade.	Surface water concentration on road washes light cinder surfacing through lead out ditch to be deposited in meadow.	Material deposited on traveled way, eroded from upslope on the road, and subsequently removed and piled here during maintenance operations.	Grass on road prism prevents loss of surface materials.

PONDING		PROPER DRAINAGE PROVISION

Ponding.	Ponding on the traveled way.	Stable backslopes and fillslopes, well drained road surfaces.	Porous road fill prevents ponding problems on the traveled way.

BERMS			PROPER DRAINAGE PROVISION

Large berm increases distributed width of road and acts to keep water channeled on traveled way.	Insloped traveled way with large berm on outside shoulder. Note the existence of rills running perpendicular to road center line even after surface blading.	Berm left during snow plowing can lead to surface water concentration on the traveled way.	Berm removal allows surface flow over downhill shoulder.

EROSION		PROPER DRAINAGE PROVISION

Backslope erosion and deposition of material on traveled way.	Surface water concentration from above causing erosion of backslope: attempt to harden slope.	Erosion susceptable backslope armored with rock rip-rap.	Rolled hay bales placed at intervals on the backslope to reduce water concentrations and erosion.

SLIDES ON THE BACKSLOPE		PROPER DRAINAGE PROVISION

Slumping backslope failure.	Slumping failure on the backslope.	Stable, well vegetated backslope.	Rock filled gabion basket protection on backslope.

SLIDES EXTENDING ABOVE BACKSLOPE			PROPER DRAINAGE PROVISION

Material above top of cut slope available for transport down to traveled way surface.	Material deposited on traveled way from a slide extending above the top of cut.	Hillslope above backslope sliding onto traveled way surface.	Stable, well vegetated backslope.

EROSION		PROPER DRAINAGE PROVISION

Surface water concentration on fillslope from grade dip outflow.	Erosion of fillslope due to concentrated surface flow.	Rock rip-rap protection on the fillslope.	Stable, well vegetated fillslope.

TENSION CRACKS		PROPER DRAINAGE PROVISION

Tension crack in traveled way due to excessive weight of saturated embankment.	Tension cracks in asphalt surface due to embankment settlement.	Well drained outslope road resists tension cracking.

SLIDES	PROPER DRAINAGE PROVISION

Over steepened fillslope slide.	Grouted rock retaining wall to stabilize fillslope.	Precast concrete log crib structure to stabilize fillslope.

EROSION	PROPER DRAINAGE PROVISION

Erosion and downcutting of inboard ditch.	Ditch pavement to resist erosion and subsequent sedimentation.	Grouted rock lead out ditch resists erosion.

SEDIMENTATION		PROPER DRAINAGE PROVISION

Clogging of ditch with sediment from upslope road segment.	Deposition, clogging of lead out ditch with light cinder surfacing washed from traveled way.	Properly functioning lead out ditch.	Well vegetated ditch reduces downstream sedimentation.

BACKSLOPE UNDERMINING	PROPER DRAINAGE PROVISION

Undermining of backslope due to downcutting of ditch.	Paved ditch resists erosion and downcutting.	Well vegetated ditch reduces backslope undermining.

PRISM SATURATION	PROPER DRAINAGE PROVISION

Backslope seepage causing saturated road subgrade.	View of porous fill built over area saturated by exfiltration of subsurface flow.	Porous fill prevents prism saturation problems due to intercepted subsurface flow.

EROSION/RUTTING		PROPER DRAINAGE PROVISION

Erosion and rutting potential due to subsurface flow interception by the prism.		Porous fill provides hardened riding surface to resist erosion and rutting.

PONDING		PROPER DRAINAGE PROVISION

Ponding problems due to subsurface flow interception by the prism.	Ponding problem on traveled way due to intercepted subsurface flow.	Built-up porous fill relieves ponding problems by providing drainage in areas exhibiting exfiltration of subsurface flow.

EROSION OF CROSS DRAIN	PROPER DRAINAGE PROVISION

Erosion of grade dip.	Grouted rock lead out ditch resists erosion.	Uniformly graded rock used to armor cross drain.

United States Department of Agriculture

Forest Services

Technology & Development Program

7700—Transportation Systems 2500 Watershed & Air Mgmt September 2000 0077 1803—SDTDC

United States
Department of
Agriculture

Technology &
Development
Program

7700—Transportation Systems
2500 Watershed & Air Mgmt
September 2000
0077 1803—SDTDC

DEPOSITION		PROPER DRAINAGE PROVISION

Filling in of grade dip outflow with sediment.	Deposition of light cinder road surfacing in meadow and clogging of lead out ditch.	Hardened upslope surface resists erosion, allowing this grade dip outflow to remain free flowing.

BYPASSED STRUCTURE		PROPER DRAINAGE PROVISION

Bypassing of cross drain outflow due to deposition of sediment.	Bypassed lead out ditch due to insloped traveled way surface shape.	Lack of bypass problems on lead out ditch.

INLET PLUGGING		PROPER DRAINAGE PROVISION

Ditch relief culvert subject to sediment plugging.	Ditch relief culvert on the verge of plugging due to sedimentation in inlet basin.	Cast in place concrete catch basin creates swirling action that flushes organic debris and sediment through cross drain culvert.	Ditch relief culvert inlet plugging prevented by concrete “L” shaped structure.

INLET BYPASSING		PROPER DRAINAGE PROVISION

Ditch erosion downstream of bypassed ditch relief culvert inlet.	Bypassed cross drain culvert due to complete burial under sediment.	Cast in place concrete catch basin functions as a ditch dam to prevent inlet bypassing.	Ditch relief culvert inlet bypassing prevented by concrete “L” shaped structure.

CORRODED OR DAMAGED PIPE		PROPER DRAINAGE PROVISION

Cross drain pipe inlet dented during maintenance operation contributes to deposition in inlet basin.	Ditch relief culvert failure due to crushed pipe inlet.	Concrete cross drain pipe resists corrosion and damage.

INSTABILITY BELOW THE OUTLET	PROPER DRAINAGE PROVISION

Ditch relief culvert outlet “shotgunned” due to fillslope erosion and instability.	Rock retaining wall to increase stability of fill over ditch relief culvert.	Member of a set of closely spaced ditch relief culverts minimizes affects to surroundings.

OUTLET SCOUR	PROPER DRAINAGE PROVISION

Scour at ditch relief culvert outlet.	Dry laid rock masonry with sill built by CCC reduces outlet scour.	Member of a set of closely spaced ditch relief culverts minimizes affects to surroundings.

INADEQUATE PIPE COVER			PROPER DRAINAGE PROVISION

Inadequate cover over pipe.	Inadequate cover over corrugated metal pipe approximately 0.15m (6 in) deep where 0.3m (12 in) is required.	Inadequate cover over pipe.	Ample cover on ditch relief culvert.

EROSION	PROPER DRAINAGE PROVISION

Gully erosion resulting in increased drainage density due to excess surface water concentration from traveled way.	Elevated CMP inlet/elbow encourages ponding, deposition, and soil moisture recharge, while buffering downstream flows and reducing erosion.	Successful seeding and revegetation reduces erosion and channel development upstream of a road drainage structure.

SEDIMENTATION		PROPER DRAINAGE PROVISION

Deposition upstream of road stream crossing due to inadequate pipe capacity.	Channel bottom clogged with light cinder surfacing from road.	Sedimentation pond causes deposition in desired location and protects downstream areas.