SCHEDULE ROADSIDE DITCH REVISITED Revisiting the roadside ditch

SCHEDULE

ROAD-SIDE DITCH REVISITED Revisiting the road-side ditch problem: By how much is the contributing area of each stream cell increased in shifting from natural downhill routing to roadside ditch interception? Does the resulting change look different if you use relative vs. absolute change?

ROAD-SIDE DITCH REVISITED Revisiting the road-side ditch question: Water flows faster in ditches than through the soil. If you count the ditch segments that feed directly into streams as part of the stream network, then map the flow length to streams with and without road ditches. By how much is the average flowlength above a stream cell reduced by adding the roads?

RAIN-ON-SNOW REVISITED Runoff from stands in the rain on snow zone is more sensitive to harvest. Streams that have much of their contributing area in the rain on snow zone must be similarly sensitive. If the rain-on-snow zone is 900 -1200 m, map the fraction of the contributing area of each stream reach that is in the rain on snow zone.

RAIN-ON-SNOW REVISITED We might want to put special restrictions on the rain on snow slopes above the most sensitive reaches. Identify the stream cells whose contributing area is mostly in the rain-on-snow zone Identify the rain-on-snow cells that contribute to these most sensitive stream reaches.

OUTLINE • Transportation Cost • Streams • Haul Routing • Example

Transportation Cost Consider some rough cost values • Skidding $30 -$60/mbf @500’ayd • Cable yarding $60 -$140/mbf @1000’ayd • Truck Haul $1/mbf/mile Combine using nested. con functions

STREAMS Prohibited areas such as streams • can be modeled by very high costs • or excluded with NULL DATA How do you handle road-stream crossings?

HAUL ROUTING Water flows down topographic gradient Traffic flows down cost gradient Hydrologic functions can then be used to identify traffic patterns.

Example In this project, the ‘source’ cells are the last segments of the roads leading to the mill: Roads#=223 & Roads#=256 What is the skidding cost in $/mbf/ft if the average skidding cost is $30/mbf for a setting with an average skidding distance of 500’ Map skidding costs using this single cost everywhere across the landscape (no roads). Add roads with an appropriate truck haul cost, and rerun. Recalculate skidding costs assuming skidding costs increase linearally from $30/mbf for flat topography to $60/mbf for 40% slopes. Rerun haul.

Example (continued) Revise cost grid to prohibit skidding (but not truck haul) across streams. Soil erosion increases with soil disturbance. For each cell, calculate its traffic volume (number of cells that are accessed by skidding/driving over that cell). Which nonroad cells get the most traffic? Should we add a road there? We might want to eliminate some of our road density. Identify and eliminate the road segments that carry the least traffic. By how much does this increase transport costs, averaged over the planning area?