Rangitata River Appeal - Sediment Study

The appeal group has been working through the appeal process, attending mediations, trying to get better outcomes for the river, and an area that has become a real focal point is the lack of any data relating to sediment accumulations in the river. This is particularly evident in the lower river, as it's there where the water spreads out and slows down and where the sediment has a chance to drop out and accumulate.

This has the effect of smothering all of the good things that live there, that provide food for the birds that live in these areas, and also both native and introduced fish species.

Salmon Anglers have been jumping up and down about this for sometime, unfortunately though there have been no studies of the river in any detail to actually measure what is going on sediment wise.

Fortunately the appeal group has managed to team up with an expert on these matters; Professor James Brasington from the University of Waikato.

James has a fancy Lidar machine that can measure the River Bed in incredible detail, which will provide a baseline to measure any changes against;

 

An image of sediments in the Rangitata River

 

The Lidar analysis of the same area can provide incredible detail

 

Compared to the old methods of physically surveying individual reaches in a riverbed that is very complex and regularly changing, as these braided river do, James can record in incredible detail the many aspects that make up the structure of the braided features and map very accurately the sediment depositions in the river, it provides a vastly superior amount of data that can then be analysed in many different ways to accurately show how the river structure may or may not be changing over time. It's just the sort of info the appellant group has been desperately short of, a real game changer going forward!

 

S Gerard
Trustee
Future Rivers