Without mountain ranges in the SW of Western Australia, even with low rainfall, drainage of water from vast areas of land is slow, resulting in elevated watertables and water logging which lead to salinity. There are thousands of locations around the Wheatbelt where roads act as severe impediments to surface and subterranean water flows.
The lack of a formal education in forestry and environmental science has resulted in common sense and intuition guiding the research undertaken at 'Auria'.
With drains installed through the local catchment and the 'Auria' property located across the neck through which all out-flowing water must pass, some interesting observations have been made. Flood plains consist of topsoils washed down over milennia, from higher in the catchment. As gravity acts downwards, not horizontally, lateral flow of water through fine clays into 2metre deep drains, is very slow. It has become abundantly obvious that many trees pump water from considerably greater depths than the floors of drains, thus encouraging water to flow down from the surface to vacated voids, well below the surface, taking with it disolved salts.
Due to the shallow gradients within the landscape, movement of surface water out of catchments is slow, and it is further impeded by roads constructed across the floodplains. Culverts installed below roads will block up with sediment if they are too small in diameter and set too low in the ground, so inevitably they were installed on or close to the surface. As a result water only flows through them when the land upstream is flooded as seen in the photo and very few trees cans survive in waterlogged ground. The compaction caused by traffic over many years means that the ground below the roads is like a dam, holding back subterranean water flow.
In recognition of this, the downstream neighbour was approached with a proposal to plant trees on his land, to encourage subterranean water flow beneath the road that constitues the boundary between his property and 'Auria' and hopefully reducing seasonal flooding and waterlogging on the 'Auria' property. As a result of the conversation, in 2016 thousands of trees were planted in a wide belt on his land,adjacent and parallel to the road.
While that land was also badly salt-degraded, as of February 2017, survival rates are looking good which augers well for the the outcome of the project.