Percentage of impervious area of contiguous watersheds.

02-03-2023 06:01 AM
New Contributor

Hello all,

I would like to determine the percentage of impervious area within watersheds of buildings. With this I want to estimate how much water flows to the building in case of heavy rain.
I have "buildings" and "impervious areas" (for example parking lots, roads, etc) as a shapefile as well as a DEM 1.
My idea was to use the zonal statistics as a table. To do this, I would have created a grid for the entire area from the "impervious area" shapefile, where the impervious areas gets a 1 and the pervious areas gets a zero. Based on the watersheds of the buildings, I would have done the zonal statistics. So the sum of all the values of the "impervious areas" grid within the watersheds.
My problem is that with the watershed function I only get subbasin. This means that individual watersheds only extend to the nearest building but not beyond, even though they are upstream.
So I would need an evaluation of the watersheds where the individual subbasins are also allowed to overlap.

I have uploaded an example image. At the moment I can only manage to determine the percentage of impervious area for watershed 1 and watershed 2 separately, although for watershed 2 the percentage in watershed 1 would also have to be taken into account.

I hope you could understand my explanations, otherwise please ask!

Does anyone have any ideas on this or perhaps have a completely different way for me? I would be very grateful!

Best regards,

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