Working for Wetlands supports rehabilitation in Craigieburn
In terms of the structural rehabilitation, Working for Wetlands has been busy with two major structural rehabilitation interventions. Within the stream channel, a number of head-cuts threatened the wetlands as they had been very actively eroding and continuing to propagate upstream into the respective portions.
The rehabilitation project consisted primarily of two erosion control structures, a smaller concrete weir to deal with the lesser headcut threatening a first portion,
and a larger gabion weir to deal with the greater weir threatening a second wetland portion 2.
The concrete weir was also designed to raise the water the water table in Portion 1, based on the observation that prior to rehabilitation that the water table became markedly lower towards the head cut. This would appear to have resulted from the loss to erosion of a fine sediment ‘plug’ at the toe end of Portion 1 that served to retard the lateral movement of water through this part of the wetland. This contrasted with the Portion 2, where only a slight lowering of the water table was observed towards the headcut at its toe.
Based on pre- and post-intervention hydrological modelling, Riddell (2007) documents how the concrete weir has been very successful at resulting in a general trend of elevating the water table, particularly in the toe of the first portion. This is despite the ‘post-’ period (2007) being a drier year than the ‘pre-' period (2006).