Barriers and Carriers - Dams beneath the surface soil.

There are many examples of dykes in the Avon Catchment. Understanding how dykes affect the flow of water and the watertable assists farmers in adopting sustainable farming practices. This in turn, assists in reducing the salinity of the soil. This example was found in ironstone near Southern Cross.
Dykes Dykes are molten rock which have been pushed up through the earth's crust. These dykes consist of very different material to that of the surrounding soils. These can be dolerite weathered down to red clays. They are relatively impervious compared to the surrounding material and act as underground dams holding the subsurface water back. Eventually damming it to the soil surface. Evaporation occurs causing salt build up at the soil surface.
Sandplain Seep These occur throughout the slopes of the catchment usually in large sandplain areas where rainfall enters (recharge) and seeps to the surface lower down the slope usually at the change of land slope. (Steep land changes to flatter valley floors.)
Steep Sided Valleys In a well shaped valley system, the lower valley bottom fills with excess water and saturates the soil. Evaporation causes salt to build up leaving a white crust usually confined to a narrow band running along the valley floor.
Flat Valleys This refers to a broad flat valley (may be many kilometres wide). The lower valley bottom fills with excess water and saturates the soil. Evaporation at soil surface causes salt to build up leaving a white crust. This can affect many thousands of hectares with small changes in watertable level affecting large areas of land (unlike steep sided valleys).
Hillside Seep Bedrock High These occur usually in mid to upper slopes of a catchment. There may be a variation in the rock or clay basement material which may come close or even directly to the soil surface. This causes the water to dam up behind it and eventually seeps to the soil surface with evaporation causing salt to build up on the soil surface.