Relative Elevation Model

Unlike a standard elevation model which shows height above a zero datum, a relative elevation model shows height relative to a trend surface. In this case, the trend surface is the average downward slope of the river as it flows to the sea.

In the relative elevation model, the main channel has a relative elevation of zero, with elevation increasing away from this channel.

The other significant channels are clearly visible, but so too are minor historic channels that now exist in the flood plain.