I’ve recently been working more in HEC-RAS and decided to have a bit of fun. Since I had already built a 3D model of  Wellington for my 3D printing project I thought, why not make some crazy flooding scenarios of the city.

However, before I could get started there was still a problem with the terrain model. The model was based off of the 1m DEM from LINZ which cut off water bodies at the water surface level. While it isn’t actually necessary have the bathymetry data for overland flooding, I wanted to have the option of dropping the waterline below sea level and also capture more realistic water depths. 

After a lot of searching I was not able to find detailed bathymetry data for the Wellington Harbour and Fitzroy Bay readily available. After contacting NIWA and they were able to provide me with a 10 meter DEM for most of Wellington Harbour and parts of Fitzroy Bay shown below. 

I merged the bathymetry data with my terrain model, and most of Wellington Harbour was complete but there were still large gaps in the channel leading into the harbour and Fitzroy Bay (lower left). Using sounding point and contour data for reference, I interpolated the missing areas in the terrain (lower right).

The animation below shows the difference between my old terrain model and the new model with the harbour bed incorporated.

I’ll note that this is a hobby project, and data is not a final or official production, but it will serve for my purposes.

Results from a preliminary flooding model are shown in the following video. Do not panic, this is the result of me throwing close to 40 meters of water at Fitzroy Bay, a rather unlikely event.

Play time aside, I’m looking forward to building multiple scenarios using project sea-rise levels and sharing those in a later post.