UW Forest EngineeringKrogstad, Rogers & Schiess Comparing Environmental Impacts of Long-reach vs. Conventional Skyline Design Options Finn Krogstad, Luke Rogers, and Peter Schiess University of Washington, Seattle

UW Forest EngineeringKrogstad, Rogers & Schiess The Opportunity Current regulations tend to discourage flying through or even hanging cable in riparian stands. This leads to more roads, less skyline deflection and increased sediment impacts from both. To justify riparian impacts (canopy) intrinsic to longer cable spans, we need to quantify the environmental impacts of soil disturbance and additional roads.

UW Forest EngineeringKrogstad, Rogers & Schiess Our Approach This paper provides an intuitive approach to estimating sediment delivery from cable yarding induced soil disturbance. This approach helps identify how longer spans can dramatically reduce sediment delivery to streams, though increasing riparian canopy disturbance.

UW Forest EngineeringKrogstad, Rogers & Schiess Overview Tradeoffs in Harvest DesignTradeoffs in Harvest Design Example: Prospector CreekExample: Prospector Creek Mapping Soil DisturbanceMapping Soil Disturbance Sediment DeliverySediment Delivery Where Do We Go From Here?Where Do We Go From Here?

UW Forest EngineeringKrogstad, Rogers & Schiess Environmental Tradeoffs of Tailhold Locations Ground Level Riparian Tailhold -minimizes riparian impact -maximizes soil disturbance, especially near stream

UW Forest EngineeringKrogstad, Rogers & Schiess Environmental Tradeoffs of Tailhold Locations Riparian Tailtree -minor riparian impact -partial suspension reduces soil disturbance

UW Forest EngineeringKrogstad, Rogers & Schiess Environmental Tradeoffs of Tailhold Locations Tailhold across riparian zone -some cable damage to riparian stand -no soil disturbance near riparian zone

UW Forest EngineeringKrogstad, Rogers & Schiess Environmental Tradeoffs of Tailhold Locations Tailhold on far side of valley -reduction in road densities -minimizes soil disturbance -increased yarding costs

UW Forest EngineeringKrogstad, Rogers & Schiess Necessary Tools and Data PROGRAMS –ARC/INFO –LOGGERPC DATA –Contours –Digital Elevation Model –Helpful to have stream, road & timber data –As always, the analysis is only as good as the data that goes into it

UW Forest EngineeringKrogstad, Rogers & Schiess ArcInfoLoggerPC Landing Location Generate Profile Data Convert Profiles to LoggerPC X,Y,Z Format Import X,Y,Z Profile Data Profile Analysis LoggerPC Report Conversion to ArcInfo Generate Format Recreate Profiles with Suspension Data Convert Profiles to ArcGRIDformat ArcGRID Sediment Analysis Yarders Carriages Cable System Contours Streams Roads Max EYD # of Cable Roads Profile Spacing Cell Size Mapping Soil Disturbance

UW Forest EngineeringKrogstad, Rogers & Schiess Getting Data Out of Arc Interactive program prompts users for a maximum EYD and the number of cable roads for each landing.

UW Forest EngineeringKrogstad, Rogers & Schiess Digitizing Landings Multiple redundant landings can be located in the same harvest unit, then analyzed for total sediment impact.

UW Forest EngineeringKrogstad, Rogers & Schiess Hanging Across StreamHanging Across Valley Mapping Soil Disturbance

UW Forest EngineeringKrogstad, Rogers & Schiess 1. Assume all soil disturbances produce equal sediment 2. Sediment delivery is a negative exponential distance function 3. Sediment filtering is reduced by soil saturation 4. Soil saturation increases with upslope area 5. Sum downslope filtering to get delivered fraction Sediment Delivery

UW Forest EngineeringKrogstad, Rogers & Schiess Sediment Filtering Fine sediment delivered to the stream unless filtered by soil, vegetation, or litter. Filtering is a negative exponential process: q(x)=q 0 exp(-ax) x: distance downslope q0: initial sediment q(x): delivered to x a: filter coefficient

UW Forest EngineeringKrogstad, Rogers & Schiess Filtering Coefficient Saturation allows sediment to bypass filters h=Q/TS h: saturated thickness (length) Q: saturated flow (volume/time) T: soil hydraulic transmissivity (area/time) S: local slope gradient (length/length) Filter coefficient a  1/h  S/Q

UW Forest EngineeringKrogstad, Rogers & Schiess Sediment Filtering Fraction of sediment reaching the stream q(x)/q 0 =exp(-  a) Sediment Filtering = (slope)/(contributing area)

UW Forest EngineeringKrogstad, Rogers & Schiess Across Stream Across Valley Probability of sediment delivery Soil disturbance Comparing Yarding Options

UW Forest EngineeringKrogstad, Rogers & Schiess Sediment Delivery Factors Management - disturbance of vegetation and litter cover Soil - silt and clay inhibit infiltration Precipitation - storm intensities Contributing Area - the area above each disturbed site can affect sediment delivery Slope - steeper slope > greater hydraulic gradient > thinner saturated layer > less overland flow > less sediment delivery

UW Forest EngineeringKrogstad, Rogers & Schiess Modeling Cumulative Impact coarse sediment fine sediment peak flows LWD shade cumulative impact stream sensitivity/resource vulnerability stands/roads topography soils harvesting construction fire/blowdown Events GIS mass wasting surface erosion rain-on-snow/ road interception

UW Forest EngineeringKrogstad, Rogers & Schiess Where do we go from here ? Develop P.L.A.N.S interface for larger study areas, or incorporate skyline analysis into Arc/InfoDevelop P.L.A.N.S interface for larger study areas, or incorporate skyline analysis into Arc/Info Begin to quantify likely sediment deliveryBegin to quantify likely sediment delivery Ultimately, we could begin to assign a cost to sediment, answering the question… What is the cost to the landowner of minimizing sediment input?Ultimately, we could begin to assign a cost to sediment, answering the question… What is the cost to the landowner of minimizing sediment input?

UW Forest EngineeringKrogstad, Rogers & Schiess