I am trying to create a flood inundation map in QGIS from known flood volumes at specific points across a raster DEM. I could potentially do this manually for each individual point using contours surrounding the point and estimating the volume of the contours until the contour volume equals the flood volume. However, these would be very tedious, so I'm looking for a tool that would do this automatically.

I am trying to create a flood inundation map in QGIS from known flood volumes at specific points across a raster DEM. I could potentially do this manually for each individual point using contours surrounding the point and estimating the volume of the contours until the contour volume equals the flood volume. However, these would be very tedious, so I'm looking for a tool that would do this automatically.

The attached picture describes what I'm trying to do, except that I am assuming that the water surface elevation is constant for simplicity. I'd apply a volume at a point on a DEM of the ground surface, and would like to extract the flood extent / depths based on that volume.