A. Erosion Risk Assessment: Erosion risk shall be determined as follows:
1. Slope: Slope, measured in percent, as an average across the area to be disturbed.
Gradient | Point Value |
10% | 1 |
>10% and 25% | 5 |
>25% | 10 |
2. Soil K Factor: Soil K factor, for water erosion susceptibility, as indicated in the "Soil Survey Of Kootenai County Area, Idaho", or other supplementary study. The highest K factor within the proposed disturbed soil profile will be used. Soil type from the soil survey will be verified on site by physical description.
K Factor | Point Value |
0.2 | 1 |
>0.2 and 0.4 | 3 |
>0.4 | 5 |
3. Proximity To Surface Water: Proximity to surface water or any feature which conveys water to surface water. Surface water includes all lakes, rivers, streams, wetlands, and similar features. Conveyance features may include natural or manmade ditches. Ponds, springs, or similar features that are contained within the property shall not be considered surface water features. Distance is measured along the slope from the closest boundary of the proposed disturbance to the conveyance or surface water feature.
Distance | Point Value |
>500' | 1 |
>200' and 500' | 5 |
200' | 10 |
4. Disturbed Area: Amount of disturbed area, expressed as a percentage of the parcel area. Areas to be disturbed during installation of utilities must be included.
Disturbed Portion | Point Value |
33% | 1 |
>33% and 66% | 5 |
>66% | 10 |
5. Buffer Strip: If the project has a usable buffer strip which provides the appropriate level of treatment for the type of project proposed, subtract ten (10) points.
6. Risk Category: The points for each factor shall be added and the risk category shall be determined from the point total as follows:
Point Total | Risk Category |
0 - 10 | Low risk |
1 - 20 | Moderate risk |
>20 | High risk |
B. Stormwater Risk Assessment: Stormwater risk shall be determined as follows:
1. Slope: Slope, measured in percent, as an average across the area to be disturbed.
Gradient | Point Value |
5% | 0 |
>5% and 10% | 3 |
>10% and 15% | 6 |
>15% and 25% | 10 |
>25% | 15 |
2. Soil Permeability: Soil permeability, measured in inches per hour as indicated in the "Soil Survey Of Kootenai County Area, Idaho", or other supplementary study. The lowest permeability in the soil horizon shall be used. Soil type from the soil survey will be verified on site by physical description.
Permeability | Point Value |
0.5 | 0 |
<0.5 | 5 |
3. Proximity To Surface Water: Proximity to surface water or any feature which conveys water to surface water. Surface water includes all lakes, rivers, streams, wetlands, and similar features. Conveyance features may include natural or manmade ditches. Ponds, springs, or similar features that are contained within the property shall not be considered surface water features. Distance is measured along the slope from the closest boundary of the proposed disturbance to the conveyance or surface water feature.
Distance | Point Value |
>500' | 0 |
>200' and 500' | 7 |
200' | 15 |
4. Impervious Surfaces: Impervious area ratio, expressed as a percentage of the parcel area covered with impervious surfaces.
Coverage | Point Value |
<20% | 0 |
20% and <40% | 5 |
40% | 10 |
5. Total Impervious Area: Total impervious area, expressed in square feet.
Coverage | Point Value |
20,000 sq. ft. | 5 |
<20,000 sq. ft. | 0 |
6. Drainage Crossing: Drainage crossing proposed. If the project requires crossing a conveyance channel or drainage, add five (5) points.
7. Buffer Strip: If the project has a usable buffer strip which provides the appropriate level of treatment for the type of project proposed, subtract ten (10) points.
8. Risk Category: The points for each factor shall be added and the risk category shall be determined from the point total as follows:
Point Total | Risk Category |
0 - 10 | Low risk |
11 - 20 | Moderate risk |
> 20 | High risk |
(Ord. 493, 6-9-2016; amd. Ord. 546, 10-17-2019)