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1. For ‘Output raster’, rename the raster from Reclassify_Clip to “FlowlineReclass”.
2. Ensure that your Geoprocessing pane appears as shown below and click Run.
   
   

Notice that the extent of the output file is now in the shape of the subbasin.

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1. At the top left of the Geoprocessing pane, click the Back button.
2. In the search box, type "build raster".
3. Click the Build Raster Attribute Table tool.
4. For 'Input Raster', select the FlowlineReclass layer and click Run.
5. Once again, open the attribute table for the FlowlineReclass layer and note that the number of cells that have been assigned a 0 have decreased to reflect the clipped geometry.
6. Close all attribute tables.
7. In the Contents pane, remove the Reclassify layer.

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1. At the top left of the Geoprocessing pane, click the Back button.
2. In the search box, type "euclidean".
3. Click the Euclidean Distance tool.
4. For ‘Input raster or feature source data’, select the Flowlines_StatePlane layer.
5. For ‘Output distance raster’, rename the raster from “EucDist_Flow1” to “FlowlineDistance”.
6. At the top of the Geoprocessing window, clickClick the Environments tab on the right.
7. For 'Extent', select Same As layer: DEMft.
8. For ‘Cell Size’, select Same as layer DEMft.
9. For ‘Snap Raster’, select the DEMft raster.

In order to output a raster with the desired geometry of the subbasin, you must apply a mask.   Without a mask, the output raster will be a rectangle containing the subbasin geometry, as seen before.

1. For 'Mask’, select the Subbasin_StatePlane layer.

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1. Click the Parameters tab.
2. Ensure your Geoprocessing pane appears as shown below

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1. and click Run.
   

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2. In the Contents pane, right

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1. -click the FlowlineDistance layer and

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1. select Symbology.
2. For 'Primary symbology', select Classify.
3. For 'Method', select Quantile.
4. For 'Classes', select 5.
   
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You Select Quantile for Method and 5 for classes.
Image RemovedYou should now see cells that vary in color the farther away they are from the nearest flowline.

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Performing map algebra

Finally, you are ready to perform the reconditioning step. You can think of this as digging a trench with a funnel-shaped cross-section along each flowline to ensure that water will flow in the intended direction. The math behind this step is explained in the diagram below and all units are in feet, since the State Plane Texas South Central project stores XY coordinates in feet and since you also recalculated the Z elevations in Lab 2 in feet.

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1. At the bottom of the Symbology pane, click the Geoprocessing tab..
2. At the top left of the Geoprocessing pane, click the Back button.
3. In the search box, type "calculator".
4. Click the Raster Calculator

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1.  (Spatial Analyst Tools) tool.

When entering expressions in the raster calculator, your syntax must be exact, so though you could technically type in the equation below, we’d recommend entering everything by clicking the mouse, so you do not get any syntax errors (at least until you’ve learned the proper syntax).

1. By double-clicking the

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1. 'Raster' layer names and 'Tools' operations and typing the numbers, enter the following equation: "DEMft" - 30 * "FlowlineReclass" - 0.02 * (1500 - "FlowlineDistance") * ("FlowlineDistance" < 1500).
2. For ‘Output raster’, rename the raster from “demft_raster” to “DEMRecon”.
3. Ensure your Geoprocessing pane appears as shown below and click Run.
   

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You should notice Notice that the DEMRecon layer looks very similar to the original DEMft. To better understand the difference between the two, you will actually calculate the difference between their corresponding values.

Click the Tools tab.

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1. In the geoprocessing pane, delete all text from the 'Map Algebra expression' box.
2. Using the same clicking technique as before, enter the following equation: "DEMft” – “DEMRecon”.
3. For ‘Output raster’, rename the raster from DEMRecon to “DEMDiff”.
4. Ensure your Geoprocessing pane appears as shown below and click Run.
   

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The DEMDiff layer displays the amount of "earth" that has been removed through the reconditioning process.

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