Aquatic risk ratings key
I. Field-measured variables
A. Adjacency to fish-bearing streams (FISH)
1 = road not near fish-bearing stream
3 = road close to fish-bearing stream
5 = road directly adjacent to fish-bearing streamB. Perennial stream crossings (STR)
1 = no perennial stream crossings per mile
3 = 1-2 perennial stream crossings per mile
5 = 3 or more perennial stream crossings per mileC. Culvert fill failure hazard (CULV)
1 = fill heights of the majority of perennial stream crossings less than 5'
3 = fill heights of the majority of perennial stream crossings 5-10'
5 = fill heights of the majority of perennial stream crossings greater than 10'D. Sideslope steepness (%SLP)
1 = 0-10% of road length with sideslopes greater than 50% steepness
2 = 10-25% of road length with sideslopes greater than 50% steepness
3 = 25-50% of road length with sideslopes greater than 50% steepness
4 = 50-75% of road length with sideslopes greater than 50% steepness
5 = 75-100% of road length with sideslopes greater than 50% steepnessE. Sustained steep road gradient (GRD)
1 = <10% of road length with a sustained grade >14% in excess of 500' long
2 = 10-25% of road length with a sustained grade >14% in excess of 500' long
3 = 25-50% of road length with a sustained grade >14% in excess of 500' long
4 = 50-75% of road length with a sustained grade >14% in excess of 500' long
5 = 75-100% of road length with a sustained grade >14% in excess of 500' longF. Road prism stability (STAB)
1 = no unstable sites
2 = 1-3 unstable sites per mile
3 = 4-6 unstable sites per mile
4 = 7-9 unstable sites per mile
5 = >9 unstable sites per mile
II. GIS-derived measures
A. Road age (AGE)
1 = road built after 1990
2 = road built 1980-1989
3 = road built 1970-1979
4 = road built 1960-1969
5 = road built before 1960B. Shallow, steep soils (SHAL_SOIL)
1 = <35% of road length on shallow soils and steep slopes (>70% steepness)
3 = 35-70% of road length on shallow soils and steep slopes (>70% steepness)
5 = >70% of road length on shallow soils and steep slopes (>70% steepness)C. Slope position (SLOPE_POSITION)
1 = majority of the road in upper slope position
3 = majority of the road in lower slope position
5 = majority of the road in middle slope positionD. Rain-on-snow susceptibility - high (ROS HIGH)
1 = 0 - 19% of road length in high zone
2 = 20 - 39% of road length in high zone
3 = 40 - 59% of road length in high zone
4 = 60 - 79% of road length in high zone
5 = > 80% of road length in high zoneE. Rain-on-snow susceptibility - moderate (ROS MED)
1 = 0 - 19% of road length in moderate zone
2 = 20 - 39% of road length in moderate zone
3 = 40 - 59% of road length in moderate zone
4 = 60 - 79% of road length in moderate zone
5 = > 80% of road length in moderate zoneF. Stream/road crossing density (all classes) (RDS STR RATE)
1 = <1.0 crossing per road mile
2 = 1.0-1.99 crossings per road mile
3 = 2.0-2.99 crossings per road mile
4 = 3.0-3.99 crossings per road mile
5 = > 4.0 crossings per road mileG. Fine sediment soils (FINE SED RATE)
1 = 0 - 19% of road length in soil type
2 = 20 - 39% of road length in soil type
3 = 40 - 59% of road length in soil type
4 = 60 - 79% of road length in soil type
5 = > 80% of road length in soil type
III. Watershed process equations
A. Mass movement
1. risk of initiation, method 1 (MM RI1) = sideslope steepness + stability (x2) + slope position + road age + shallow soils + rain-on-snow susceptibility
2. risk of initiation, method 2 (MM RI2) = sideslope steepness + slope position + road age
3. transport risk, method 1 (MM TR1) = sideslope steepness + slope position + crossing density
4. transport risk, method 2 (MM TR2) = sideslope steepness (x2)+ slope position
5. potential magnitude of effect (MM ME) = fish (x2)+ culvert fill depth + crossing density
6. mass movement sum (MM SUM) = MM RI1 + MM TR1 + MM ME
B. Fine sediment inputs
1. risk of initiation (FS RI) = sideslope steepness (x2)+ road gradient (x2) + culvert fill depth + crossing density + road age + fine sediment soils
2. transport risk, method 1 (FS TR1) = sideslope steepness + slope position + crossing density
3. transport risk, method 2 (FS TR2) = sideslope steepness (x2)+ slope position
4. potential magnitude of effect (FS ME) = fish (x2)+ culvert fill depth + crossing density
5. fine sediment sum (FS SUM) = FS RI + FS TR1 + FS ME
C. Hydrologic effects
1. risk of initiation (HE RI) = sideslope steepness + slope position + shallow steep soils + rain-on-snow susceptibility
2. transport risk (HE TR) = road age + road gradient + crossing density + sideslope steepness
3. potential magnitude of effect (HE ME) = fish (x2)+ culvert fill depth + crossing density
4. hydrologic effects sum (HE SUM) = HE RI + HE TR + HE ME
D. Summary
1. watershed process summary (AQUASUM) = MM SUM + FS SUM + HE SUM
2. watershed process summary (AQUASUM2) = MMSUM*2+FSSUM*2+HESUM
3. aquatic priority (AQPR):
if AQUASUM2 >175, then AQPR = High
if AQUASUM2 100-175, then AQPR = Mod
if AQUASUM2 <100, then AQPR = Low