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Constructed Erosion Control Measures to Reduce Nutrient Losses in Runoff

Important Terms

Table 8.3.1 Key Terms and Definitions

Term Definition

Basin

Earthen structure used to store water as it runs off or is generated from upstream land or facilities. While this water is being held or ponded, solids and some contaminants can be settled out of the water column. Berm

Generally refers to a low earthern mound above natural ground level. They are used to control erosion and sedimentation by reducing the rate of surface runoff. Diversion Channel or Interception Ditch

Earthen channels that are constructed below the existing surface to contain water within its banks. Used to divert and/or control water coming onto cropped land and stop water erosion from causing nutrient loss from the soil.

Drop Structures

These structures are often characterized as a vertical drop of several feet onto a horizontal stilling basin to dissipate the energy of flowing water and allow relatively low velocities (nonerosive) to exit the drop structure area. Many types exist such as drop inlet pipe, sloped pipe, chute spillways, grade controls and lined waterways.

Geotextiles

These are permeable, durable fabrics which, when used in association with soil, have the ability to separate, filter, or drain liquid and reinforce or protect soil. Filter cloth is commonly used term for a widely used fabric to keep fine soil particles from washing out from below higher cost materials or structures. Grassed Waterways

Broad, shallow, saucer-shaped channels, which are grassed and designed to move surface water across farmland without causing soil erosion. Gullies

A small valley or ravine worn away by running water and serving as a drainage-way after prolonged heavy rains.

Ponding Water that collects in small depressions, into a pond or large puddle. Run-on

Surface water originating upslope of a particular parcel of land. This water may be from natural runoff from upslope land parcels, natural areas or controlled releases from facilities. Sheet Flow or Sheet Runoff Runoff that flows uniformly across the landscape and not in concentrated channels or gullies. Vegetative Field Borders (VFB)

Areas of natural or managed vegetation located at the edge of a cropped field to retain and buffer the passage of nutrients onto another land parcel, watercourse or water body. Water Bodies Bodies of surface water, including lakes, streams, rivers, wetlands and sloughs.

This chapter looks at more intensive control measures to deal with runoff from snowmelt or rainfall on fields with long, continuous slopes with a greater than 6 % grade. This chapter focuses on constructed erosion control measures to supplement in-field management practices to reduce erosion and nutrient losses in runoff.

The control measures discussed in this chapter are often more expensive and require more planning than the practices described in the previous chapter. Services from a professional engineer may be needed. Also, in contrast to the management practices in the last chapter, their placement on cropped land may reduce the net productive area. Despite these drawbacks, these measures can dramatically reduce the amount of soil and nutrients loss from high-risk areas for many years and even decades if they are properly designed and maintained.