Erosion is the process by which the land surface is worn away by the action of wind, water, ice, or gravity - it is the process where soil particles are dislodged or detached and put in motion.

Sedimentation is the process whereby the detached particles generated by erosion are deposited elsewhere on the land or in our lakes, streams, and wetlands – Impacts on quality of quantity

Channel erosionis caused by:

• increased runoff

• removal of natural vegetation along the waterway

• channel alterations resulting from construction activities.

Overland erosion

- occurs on bare slopes as a result of:

rain splash

runoff

Overland erosion

• Sheet erosion -the removal of a uniform layer of soil

• Rill erosion - runoff is heavy and water concentrates in rivulets

• Gully erosion – when the water concentrates into an area that cannot handle the flow.

Physical Factors Affecting Erosion

• Climate - rainfall amount, intensity, frequency

• Vegetative cover - the most important physical factor influencing soil erosion

• Soil – texture (size), structure (organic matter), and cohesion (binding force)

• Slope characteristics – steepness and the length water travels

PRINCIPLES AND STRATEGIES

• plan the development to fit the particular topography, soils, waterways, and natural vegetation at a site

• expose the smallest practical area of land for the shortest possible time

• apply soil erosion prevention practices• apply sediment control practices as a

perimeter protection• Inspection and maintenance

It is much more effective to

- prevent erosion

- than to control or remove the sediment generated from erosion

Controlling Runoff – minimize exposure of bare soil

• Staging construction

• Preserving vegetation buffers

• Covering all areas with temporary seeding and mulch

• Establishing permanent seeding as soon as possible

Methods used to minimize erosion include:

• Special grading practices• Diversions• Check dams• Grade stabilization structures• Energy dissipaters• Erosion control blankets and other geotextile

materials• Snow fence• Chemical soil binders

VEGETATIVE STABILIZATION

• Before starting any earth change, critical, and sensitive areas should be identified on the site

• Temporary vegetative stabilization

- fast growing, robust plants

• Permanent vegetative stabilization

- grasses, legumes, ground cover

• Selecting plant materials

CONTROLLING SEDIMENT

• Vegetative sediment control involves using existing or newly planted vegetation to trap or filter sediment from runoff

Critical Areas

• A critical area is difficult to stabilize with vegetation once it is graded and the existing vegetation removed

• Typical critical areas would include areas with infertile subsoils, droughty soils, concentrated flow, heavy traffic, and long or steep slopes.

• Whenever possible, critical areas should not be disturbed

Sensitive areas

• Sensitive areas are those areas next to lakes or streams that can be damaged by sediment

• Similar to critical areas, it is important that sensitive areas be left undisturbed or stabilized quickly after being disturbed.

Soil conditions that may cause problems

• low fertility• acidity• too dry• too wet• The most important steps to take in

protecting new seedlings, shrubs, vines, or trees are mulching and holding the mulch in place.

SELECTING PLANT MATERIALS

• Climate

• Soils

• Slopes

• Site Use and Maintenance

METHODS TO ESTABLISH VEGETATION

• Seeding

• Sprigging

• Sodding

• Planting a root-balled or container-grown shrub or tree

Maintenance

• Periodically inspect

• fertilizer needed?

• insect damage?

• spot seeding or replanting is necessary?

Topsoil slippage

Vegetative filters

• The effectiveness of filter strips depends on flow patterns, strip width, vegetation type, and density (20 to 25 ft)

STRUCTURAL SEDIMENT CONTROL

• Perimeter Barriers

THE DIFFERENCE BETWEEN STORM WATER BASINS AND

SEDIMENTATION BASINS• Storm water basins are permanent

structures designed to replace the natural water storage of a site and provide some water quality improvement after the site is completed

• Sedimentation basins are used during construction and are specifically designed to control off-site migration of sediment.

Sedimentation Basins

• Location• Size• Side slopes should be no greater than 3:1

(horizontal to vertical)• Vegetation should be established on the

side slopes prior to use• The outlet structure should be located in or

near the embankment to allow for safe and easy access for cleaning

Sedimentation Basins

• For effective sediment control, basins should be at least four times as long as wide with the inlet and outlet at opposite ends

• If this is not possible due to site constraints, baffles should be placed within the basin to increase the water travel distance

Retention basins are constructed to collect and retain runoff

Detention basins are constructed to collect and temporarily detain runoff

Maintenance

Principal Outlet Structure

SOIL EROSION AND SEDIMENTATION CONTROL

PLANSPart 91, Soil Erosion and Sedimentation Control, of

the Natural Resources and Environmental Protection Act (NREPA), 1994 PA 451

The plan must include all strategies and control measures

that willbe used to minimize erosion and off-site sedimentation

A site location map, including the property boundaries and limits of the proposed earth change

Include in SESC Plan

Include in SESC Plan

The proximity of the earth change to lakes, streams, and wetlands

Existing vegetation and predominant land surface features

Elevation contour intervals or a description of the slopes on the site

• A description of existing and propose drainage patterns and slopes

• A description of temporary and permanent control measures

0-6 percent low erosion hazard

7-12 percent moderate erosion hazard

over 12 percent high erosion hazard

MICHIGAN’S STORM WATER PROGRAMFOR CONSTRUCTION SITES

• In 1990, the federal government published rules that required storm water discharge permits for various industrial activities.

• Construction activities that disturb five or more acres of land were included in those rules.

• As a result of the federal storm water regulations, the State of Michigan began issuing permit coverage for construction activities in 1992.

• Permit coverage is obtained through a “Permit-By-Rule” process and is tied to the statewide Soil Erosion and Sedimentation Control (SESC) Program.

• A person can become a Certified Storm Water Operator (Certified Operator) by participating in the Michigan Department of Environmental Quality’s (MDEQ), Certified Operator Training Program.

MICHIGAN’S STORM WATER PROGRAM FOR CONSTRUCTION SITES

REVISED UNIVERSAL SOIL LOSS EQUATION

• A = R x K x LS x C x P where,• A is the predicted average annual soil loss

in tons per acre• R is the rainfall-runoff erosivity factor.• K is the soil erodibility factor.• LS is the slope factor.• C is the cover-management factor.• P is the support practice factor.

C is the cover-management factor

• This factor takes into account the effects of plant growth, surface cover, and surface roughness.

• C factors range from 0.005 for dense grass or hay to 1.0 for bare soil conditions.

• The C factor for mulch is 0.200 when placed at two tons per acre.

P is the support practice factor

• Support practices include such things as terracing, contouring, and strip cropping

• The P factor for construction sites is generally considered to be 1.0.

THE DIFFERENCE BETWEEN STORM WATER BASINS AND

SEDIMENTATION BASINS• Storm water basins are permanent

structures designed to replace the natural water storage of a site and provide some water quality improvement after the site is completed

• Sedimentation basins are used during construction and are specifically designed to control off-site migration of sediment.

Sedimentation Basin Size

• Do not use RUSLE• Storage per contributing area

method• 3,600 cubic feet of Sediment per

acre• Equivalent to losing 1 inch of soil

over an arce

Amount of sediment removed from the runoff

• water velocity,

• time that the water remains in the basin,

• and the size and density of the sediment particles.

Sedimentation Basin Configuration

• surface area of the basin is more important than the depth

• depth should be a minimum of two feet (less than 80,000 cubic feet - 400 feet x 100 feet x 2 feet)

• no shallower than the average distance from the inlet to the outlet (length) divided by 200 (a basin that is 600 feet long must have a depth of 3 feet)

Example

• 10 acres

• 36,000 cubic ft

• Width = 67 ft

• Length = 469 ft

• Depth = 2 feet (a constant)