Example - Quantify length of woodland shaded channel by accumulating value across network
Scenario
You are studying the impact of shading on a river from riparian woodlands. You have been provided a polygon dataset of broadleaved woodland habitats that intersect your river network, this may have come from a satellite dataset or an existing habitat map from an environmental agency. You wish to find out for each segment of the catchment the total upstream length of shaded channel, a task that can be solved using the Accumulate network attribute tool.
Workflow
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Step |
Processing Task |
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1 |
To use the Accumulate network attribute tool the values you wish to accumulate must be an attribute of the river network. The first step is compute the intersection of the river network with the woodland dataset.
Catchment plotted over intersecting woodland habitat |
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2 |
Run the intersect tool to create a new polyline dataset.
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3 |
Run the Summary statistics tool to create a table that sums up the intersection length by polyline ID.
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4 |
Join the summed length to the network using the Join Field tool.
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5 |
Run the RivEX tool Accumulate network attribute to accumulate the joined field. In the example below the output table "AccShading" will be joined backed to the river network. You now have all the data encoded into the network for further analysis and mapping.
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6 |
In the sample images below we show the accumulated upstream length of shading alongside the proportion of upstream length that is shaded.
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In this example we have looked at length of channel shaded, but the attribute of interest could be anything that makes sense when accumulated in a downstream direction! |
