Estimated Cost
$412
Surface Area
5,265 sqft
Method
ECB
Slope Factor
1.05x
33% = 3:1 slope · 50% = 2:1 slope · 100% = 1:1 (45°)
Horizontal Area
5,000 sqft
Actual Surface
5,265 sqft
Slope Factor
1.053x
Extra Area
+265 sqft
ECB: Straw Single-Net
Cost per Square Foot
$0.08/sqft
High erosion risk, fine particles
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Price as of Jul 24, 2026. Product prices and availability are accurate as of the date indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
Inputs
Result
A 100×50 ft slope at 33% grade has 5,270 sq ft of actual surface area (5% more than horizontal). Straw/coconut blanket at $0.11/sqft with 1.5 staples per sq yd.
Inputs
Result
On a 50% slope, wattles are spaced every 20 ft. Five rows across 100 ft width = 500 linear ft of fiber roll, requiring 20 rolls at 25 ft each.
The best method depends on slope steepness. Straw mulch works for slopes up to 50% (2:1). Erosion control blankets handle slopes up to 100% (1:1). Turf reinforcement mats are needed for slopes steeper than 1:1. Silt fence and wattles are sediment barriers, not slope stabilization.
| Slope % | Slope Ratio | Recommended Method | Cost/sqft |
|---|---|---|---|
| 0–33% | 3:1 or flatter | Straw blanket or mulch | $0.05–$0.14 |
| 33–50% | 3:1 to 2:1 | Straw/coconut ECB | $0.08–$0.14 |
| 50–67% | 2:1 to 1.5:1 | Coconut double-net | $0.10–$0.18 |
| 67–100% | 1.5:1 to 1:1 | 100% coconut ECB | $0.14–$0.22 |
| >100% | Steeper than 1:1 | TRM (permanent) | $0.22–$0.44 |
A slope has more surface area than its horizontal projection. Multiply the horizontal area by the slope factor: sqrt(1 + (grade%/100)^2). A 50% slope (2:1) has 12% more surface area. A 100% slope (1:1) has 41% more.
| Slope % | Slope Ratio | Slope Factor | Extra Area |
|---|---|---|---|
| 25% | 4:1 | 1.031 | +3% |
| 50% | 2:1 | 1.118 | +12% |
| 100% | 1:1 | 1.414 | +41% |
| 150% | 1:1.5 | 1.803 | +80% |
The standard rate is 2 tons per acre, which equals about 1.25 bales (75 lb each) per 1,000 sq ft. One bale covers approximately 800 sq ft. Straw must be anchored on slopes over 25% with crimping or tackifier.
| Area | Bales Needed | Seed (lbs) | Approx Cost |
|---|---|---|---|
| 1,000 sq ft | 1.25 bales | 8 lbs | $40 |
| 5,000 sq ft | 6.25 bales | 40 lbs | $200 |
| 1 acre | 54 bales | 350 lbs | $1,700 |
Wattle (fiber roll) spacing follows the formula: horizontal spacing = 1000 / slope%. A 33% slope needs wattles every 30 feet, a 50% slope every 20 feet, and a 100% slope every 10 feet. Secure with wooden stakes every 4 feet.
| Slope % | Row Spacing | Rows per 100ft | Rolls per 50ft Width |
|---|---|---|---|
| 25% | 40 ft | 2–3 | 4–6 |
| 33% | 30 ft | 3–4 | 6–8 |
| 50% | 20 ft | 5 | 10 |
| 100% | 10 ft | 10 | 20 |
Hydroseeding costs $0.07-$0.35 per sq ft depending on slope steepness and seed mix. A 5,000 sq ft area on moderate slope costs about $700. Steep slopes double the cost due to extra seed and additional passes.
| Area | Flat Cost | Moderate Slope | Steep Slope |
|---|---|---|---|
| 1,000 sqft | $70–$140 | $120–$210 | $210–$350 |
| 5,000 sqft | $350–$700 | $600–$1,050 | $1,050–$1,750 |
| 1 acre | $3,000–$6,000 | $5,000–$9,000 | $9,000–$15,000 |
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Last Updated: Jul 24, 2026
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