Russell has produced some interesting topography for the river bed. He has shown the river cross sections and shape of the river banks. The 3 red lines correspond to the white markers on the river bank.
The height from the road surface to the river bed is about 6m and on the other side it’s about 7.5m from the top of the bank to the river bed. This 3D topo map will help John (the engineer) work out what the distance needs to be from the underside of the bridge to the river bed. Height is just one of the factors in the design, access and turning radii are also critical. There are standards for turning off the road so that road traffic can pass without having to stop.