Chapter 10: Appendix 185
During grading,
preparation, seeding, and mulching, large quantities of
sediment and associated chemicals may be washed into surface
prior to
plant establishment.
Crop Residue Use (344): Using plant residues to protect cultivated fields during
critical erosion periods.
When this practice is employed, raindrops are intercepted by the residue reduc-
ing detachment. soil dispersion, and soil compaction. Erosion may be reduced
and the delivery of sediment and associated pollutants to surface water may be
reduced. Reduced soil sealing, crusting and compaction allows more water to
pollutants
infiltrate, resulting in an increased potential for leaching of
into the ground water.
increase the microbial and bacterial action on
Crop residues on the
near the
Nitrates and
pesticides may be tied-up and less
and ground water: Residues trap sediment
available to be delivered to
and reduce the amount carried to
Crop residues promote soil ag-
gregation and improve soil tilth
Deferred Grazing (352): Postponing grazing or resting g-razing land for pre-
scribed period.
In areas with bare ground or low percent ground
deferred grazing will
reduce sediment yield because of increased ground cover; less ground
disturbance, improved soil bulk density characteristics, and greater infiltration
rates. Areas mechanically treated will have less sediment yield when deferred to
encourage revegetation. Animal waste would not be available to the area during
the time of deferred grazing and there would be less opportunity for adverse
runoff effects on surface or aquifer water quality. As vegetative cover increases,
the filtering processes are enhanced, thus trapping more silt and nutrients as
well as snow if climatic conditions for snow exist. Increased plant cover results
a greater uptake and utilization of plant nutrients.
Dikes (356): An embankment constructed of earth or other suitable materials to
protect land against overflow or to regulate water.
Where dikes are used to prevent water from flowing onto the floodplain, the
pollution dispersion effect of the temporary wetlands and backwater are de-
creased. The sediment, sediment-attached, and soluble materials being trans-
ported by the water are carried farther downstream. The final fate of these
materials must be investigated on site. Where dikes are used to retain runoff on
the floodplain or in wetlands the pollution dispersion effects of these areas
be enhanced. Sediment and related materials may be deposited, and the quality of
the water flowing into the stream from this area will be improved.
Dikes are used to prevent
and to form
The formed areas may
be fresh, brackish, or
wetlands. In tidal areas dikes are
to stop
saltwater intrusion, and to increase the hydraulic head
which will
force intruded salt water out the aquifer: During construction there is a potentia!
of heavy sediment loadings to the
When pesticides are
to
control the brush on the dikes and fertilizers are
for the establishment and
maintenance of vegetation there is the possibility for
materials to be
washed into the
waters.
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