How to find out which areas are affected by flooding due to heavy rain?

Question

I'm working on a little project to visualize affected streets of flooding due to heavy rain. I already got a DEM for my study area and filled the depressions with r.fill.dir.
Since I never worked on hydrological analysis with QGIS, I don't exactly know which workflow/tools I should use to determine the affected area of the flooding due to heavy rain. I know that in reality the affected area is a slope which channels the water downwards. I already could modelling this with r.watershed. But is there a way or a tool to calculate the area of the flooding in relation of the amount of rainfall?

MapInfoNewbie · Answer

I am unsure how accurate you want your results to be, my understanding is that you can do one of two approaches:

Find known water level points for the rainfall event and create an interpolated surface, do a quick raster calc to find areas where terrain is higher than the water surface and youll get an approximate extent of flooding.

The more standard industry practice is to use a hydraulic solver engine to get a more realistic flood extent. As you said the affected area is a slope, hence the water levels will vary across the watershed. There are several modelling tools out there, but HEC RAS 2D is a free to use solver which may be useful. TUFLOW and Flood Modeller also have free versions which may be suitable.

How to find out which areas are affected by flooding due to heavy rain?

One Answer

Add your own answers!

Ask a Question