Erosion Control Sizing Calculator

Site inputs that control quantities

Start with disturbed area and the percentage that will receive surface protection. Split complex sites into slope faces, channels, and perimeter runs. Record slope length, width, and steepness because spacing for wattles and pin density increases as slopes get steeper. Keep roll dimensions and overlap assumptions consistent with the product submittal.

Blanket and mulch coverage planning

Erosion control blankets are sized from the protected area divided by effective roll area. Effective area subtracts side and end overlaps, then a waste factor accounts for trimming, anchoring at crest and toe, and field layout losses. Mulch quantity is calculated from the same protected area multiplied by an application rate, so changing the coverage percentage updates both blanket rolls and mulch mass.

Linear controls at the perimeter

Perimeter measures drive silt fence and similar linear barriers. Use a continuous length that follows the toe of slope and around inlets, then apply waste to cover tie-ins, returns, and extra posts. When multiple discharge points exist, treat each run separately and sum lengths to avoid underestimating overlaps at junctions and terminations.

Contour wattles and channel check dams

Wattle rows are estimated from slope length divided by a practical spacing rule tied to slope percent. Total wattle length equals rows times slope width, then segments are computed from the selected segment length. For channels, check dam spacing is approximated by dam height divided by channel slope, producing a count over the channel length. This supports early material takeoffs before hydraulic modeling.

Erosion risk screening and documentation

A simple RUSLE screening value combines regional rainfall erosivity, soil erodibility, topographic LS, cover, and practice factors to classify risk bands. Use the risk result to prioritize stabilization sequencing, inspection frequency, and redundancy. Export the calculation to CSV or PDF and attach it to submittals, daily reports, and SWPPP documentation for traceable quantity decisions. Re-run the tool after grading changes, rain events, or resequencing to keep procurement aligned with current site conditions, always.

1) What does “coverage percentage” mean?

Coverage percentage is the portion of disturbed area that will receive blankets or mulch. Use 100% for full-site protection, or a smaller value when only slope faces, stockpiles, or haul roads need surface stabilization.

2) Why do overlaps reduce roll coverage?

Blanket edges must overlap to prevent undercutting and seam opening. The overlap widths and lengths are subtracted from roll dimensions to estimate effective coverage. Larger overlaps increase roll count but improve continuity in the field.

3) How should I choose a waste factor?

Waste accounts for trimming, irregular shapes, anchoring trenches, and damaged sections. For simple rectangles, 5–10% is typical. For complex layouts with many transitions and penetrations, consider 10–20% and validate against a layout sketch.

4) Are wattle spacing and staple densities design values?

They are planning guidelines that scale with slope steepness. Final spacing depends on soil, flow concentration, and product specifications. Always confirm requirements from your erosion control plan, local standards, and manufacturer installation instructions.

5) How are check dams sized in this tool?

The tool estimates check dam count from channel slope, channel length, and a selected dam height. Spacing is approximated so the crest-to-toe drop matches the dam height. Verify with hydraulic checks, allowable velocities, and sediment storage needs.

6) What does the RUSLE result tell me?

RUSLE provides a screening soil loss rate in t/ha/yr, not a permit compliance guarantee. Use it to compare scenarios, prioritize early stabilization, and justify higher protection levels on steeper or longer slopes with erodible soils.