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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.

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Presentation Transcript
the opportunity
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.
our approach
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.
overview
Overview
  • Tradeoffs in Harvest Design
  • Example: Prospector Creek
  • Mapping Soil Disturbance
  • Sediment Delivery
  • Where Do We Go From Here?
environmental tradeoffs of tailhold locations
Environmental Tradeoffs of Tailhold Locations

Ground Level Riparian Tailhold

-minimizes riparian impact

-maximizes soil disturbance, especially near stream

environmental tradeoffs of tailhold locations5
Environmental Tradeoffs of Tailhold Locations

Riparian Tailtree

-minor riparian impact

-partial suspension reduces soil disturbance

environmental tradeoffs of tailhold locations6
Environmental Tradeoffs of Tailhold Locations

Tailhold across riparian zone

-some cable damage to riparian stand

-no soil disturbance near riparian zone

environmental tradeoffs of tailhold locations7
Environmental Tradeoffs of Tailhold Locations

Tailhold on far side of valley

-reduction in road densities

-minimizes soil disturbance

-increased yarding costs

necessary tools and data
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
mapping soil disturbance
Mapping Soil Disturbance

ArcInfo

LoggerPC

Contours

Max EYD

Landing

Streams

# of Cable Roads

Location

Roads

Convert Profiles

Profile

Generate

Import X,Y,Z

to LoggerPC X,Y,Z

Spacing

Profile Data

Profile Data

Format

Yarders

Profile

Carriages

Analysis

Cable System

Recreate Profiles

Conversion to

LoggerPC

with Suspension

ArcInfo Generate

Report

Data

Format

Cell

Convert Profiles to

Size

ArcGRID

format

ArcGRID

Sediment Analysis

slide10

Getting Data Out of Arc

Interactive program

prompts users for a

maximum EYD and the

number of cable roads

for each landing.

slide11

Digitizing Landings

Multiple redundant landings can be located in the same harvest unit, then analyzed for total sediment impact.

slide12

Mapping Soil Disturbance

Hanging Across Stream

Hanging Across Valley

slide13

Sediment Delivery

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 filtering
Sediment Filtering

Fine sediment delivered to the stream unless filtered by soil, vegetation, or litter. Filtering is a negative exponential process:

q(x)=q0exp(-ax)

x: distance downslope

q0: initial sediment

q(x): delivered to x

a: filter coefficient

filtering coefficient
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

sediment filtering16
Sediment Filtering

Sediment Filtering =

(slope)/(contributing area)

Fraction of sediment

reaching the stream

q(x)/q0=exp(-a)

slide17

Comparing Yarding Options

Soil disturbance

Across Valley

Across Stream

Probability of sediment delivery

sediment delivery factors
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
modeling cumulative impact

GIS

Events

Modeling Cumulative Impact

harvesting

stands/roads

construction

topography

fire/blowdown

soils

surface

mass

rain-on-snow/

erosion

wasting

road interception

coarse

fine

peak

LWD

sediment

sediment

flows

shade

stream sensitivity/resource vulnerability

cumulative impact

where do we go from here
Where do we go from here ?
  • Develop P.L.A.N.S interface for larger study areas, or incorporate skyline analysis into Arc/Info
  • Begin 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?