The Rakaia River Catchment is a fluvial environment

1. The Rakaia River Catchment is a fluvial environment How do people use this environment? How many people live in this area? (what is the cultural geography?) What are the resources people want to use from this area?

2. How do people affect the natural environment and the natural processes? • Are the effects - Major? Minor? • Have people been Destructive? Or are they Guardians? • Do people care for the environment? Kaitiakitangi

3. The Rakaia has a Water Conservation Order Legal Protection

4. People and running water (fluvial processes) • Deforestation • Irrigation • HEP power production • Recreation use • Channel alteration

5. examples • There is withdrawal of water for irrigation from the Rakaia river. Although this is controlled withdrawal of water decreases water volume. The volume of water in any river has a direct effect on the “work” a river does – with a lower volume there will be less fluvial erosion, transport and deposition.

6. examples There are two major HEP schemes (Lake Coleridge and Highbank). Water is diverted into Lake Coleridge from the Harper, Acheron and Wilberforce rivers increasing the level of the lake. This is bringing extra sediment into the lake (fluvial deposition). Where this water enters the Rakaia river it increases the river’s volume. Water from the Rangitata River is added to the Rakaia via a diversion canal. This discharge may at times account for 20% of water in the Rakaia at the SH1 bridge. These are all examples of human modification of the drainage network which change the fluvial processes of the Rakaia river.

7. Coleridge HEP

8. examples There are a variety of measures taken in the Rakaia Catchment area to control the flooding of the river and its tributaries. Stop banks can be seen at Cleardale farm – located on the alluvial fan of Little River where it enters the main Rakaia Valley. As a result there has been increased fluvial deposition in the river channel and this must be regularly dredged to remove the alluvial deposits and keep the river within the stopbanks instead of spreading across the alluvial fan when it floods. Containing the river also means that when it floods the volume of water is increased – resulting in increased fluvial erosion. It combat this (as it would cause loss of farmland) trees have been planted on the river banks and deflection goynes used. These measures can also be seen along lower course of the Rakaia River near the sea.

9. examples Fluvial slope processes have also been changed. People have introduced stockand changed the vegetation of the area for farming. There are also recreational and transport uses. All of these uses have increased erosion and are now more controlled in an effort to stablise erosion. Examples of soil erosion resulting from fluvial slope processes can easily be observed on the steep slopes of the Mt Hutt Range. Slope processes have been increased by people removing vegetation creating larger loads in rivers, and increased deposition in the lower part of the river on the Canterbury Plains e.g Rakaia Island.

10. RMA • Can people do just what they want in this environment? • Are their controls? What are they? Who has control?