SCHEDULE

Discussion Problems Revisiting the take-home midterm: Zipping to move your project make directory c:/temp/yourname/flowacc set working directory save project there do some work, then save & close ArcView zip c:/temp/yourname/ move yourname.zip however you like extract yourname.zip to c:/temp/yourname/ double click projectname.apr This is your project, just as you left it.

Discussion Problems Revisiting the take-home midterm: Revisable themes look through the themes in the exam Which theme can be revised? Which can’t? What do each group have in common? Rewrite them so that they can be revised Redo the exam assuming everything mature Redo the exam assuming that everything burns Map the mature/burned difference in WAR

Discussion Problems Map the stream network from the midterm dem.e00 assuming that all cells with a contributing area of at least 100 cells is a stream cell. What is the area of 100 cells? Make stream networks with different contributing areas. Which one looks best? Make a grid of all stream headwaters (the first cell in each stream).

Discussion Problems 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 m, map the fraction of the contributing area of each stream reach that is in the rain on snow zone.

Discussion Problems 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.

Discussion Problems 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?

OUTLINE Flow Length Addition Multiplication

FLOW LENGTH water flows downhill, but delivery decreases with distance aGrid.FlowLength (weightGrid, upStream)

Flow Distance Filtering effects increase with distance Probability(delivery)=exp{(17.76-D)/46.43}

FLOW LENGTH: Addition Distance Pdel=(17.76-[fd].FlowLength(nil, false)/46.43).exp Time flow_rate=k*(slope) velocity=flow_rate/porosity time=1/velocity

FLOW LENGTH: Multiplication sums of logs x 1 x 2 x 3 x 4 =exp(log(x 1 x 2 x 3 x 4 )) =exp(logx 1 +logx 2 +logx 3 +logx 4 ) =flowDir.flowlength([x].log,false).exp

FLOW LENGTH: Multiplication Fractional delivery: fraction x i of input V i-1 is delivered to block i+1 so if V 1 =V 0 x 1 and V 2 =V 1 x 2 then V 2 =V 0 x 1 x 2 The delivery fraction can vary We can multiply these fractions together: V 0 x 1 x 2 x 3 x 4 =exp(log(V 0 x 1 x 2 x 3 x 4 )) =exp(logV 0 +logx 1 +logx 2 +logx 3 +logx 4 ) ([V].log+[fd].flowlength([x].log,false)).exp

FLOW LENGTH: Multiplication Probability of delivery to the next cell might decrease with local slope and disturbance [fd].flowlength(f([slope],[harvest]).ln,false).exp

Discussion Problems 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?

Practice Problem Identify FlowDirection for each cell (arrows are okay)

Practice Problem Identify FlowAccumulation(nil)

Practice Problem Identify streams as cells with >10 contributing cells

Practice Problem identify flow distance to streams