Rules and Methods of Erosion and Sediment Control
The hierarchy: keep soil in place first
The controlling idea is that erosion control prevents the problem while sediment control treats the symptom. Follow the sequence: minimize disturbed area and schedule earthwork for the dry season, preserve existing vegetation and buffers, then apply erosion control (mulch, erosion control blankets, seeding, tackifier, diversion dikes and swales), then sediment control (silt fence, fiber rolls, sediment traps and basins, inlet protection), and finally runoff control (check dams, lined channels, outlet protection, velocity dissipation). Questions love to test whether you reach for the right category - silt fence around a stockpile is sediment control; seeding and mulching that stockpile is erosion control.
Where candidates get caught
Silt fence is not a dam. It is installed on the contour with ends turned uphill and fabric trenched in, and it fails when placed in a concentrated flow path where a check dam or channel lining belongs. Erosion control blankets are selected by slope steepness, soil, and shear stress - light netting on a long, steep slope is a common wrong answer. Sediment basins need a dewatering device and a stabilized emergency spillway; a basin without them is a bathtub waiting to fail. Check dams belong in swales and ditches, spaced so the toe of one backs water to the heel of the next. Keep clean water clean by diverting it around the disturbance rather than running it through.
Rule of thumb: ask of every BMP, 'does this stop soil from moving, or catch it after it moves?' Preference order: don't disturb, protect what is there, slow the water down, trap the soil last.