Mentor: Alistair Grinham
Project Team: Nathaniel Deering, James Lockington, Robert Bowd
Land reclamation of coastal areas develops aquatic marine zones into urban terrestrial areas. Through this process there are extended periods of time where large areas of bare sand are exposed. Previous work on the bare sand zones in this reclamation area has indicated there are large quantities of sand moved during high wind events. This field based project will aim to develop green engineering solutions to reducing sand movement in a large reclamation area. This project will assist in developing knowledge and skills useful for CIVL2130.
During the previous Erosion Control project, a baseline was established for aeolian sand transportation and plantation of native costal grasses and trees. The work previously conducted progressed into monitoring of revegetation planted and implementing student lead immediate solutions.
Initially the revegetation plan appeared to provide promising results by providing small amounts of wind shielding allowing sand to collect in the wind shadows of the plants. However, over coming months the native shrubs began to die/disappear students hypnotised this to be caused by fauna eating the plants. A monitoring system was placed to try to find the cause but no direct evidence was found.
As of March 2016 all native shrubs had died and the only native grass remaining was spinifex, which appears to be thriving and producing large roots for expansion. Over the proceeding months this expansion subsided and the spinifex appeared to be struggling with the drier autumn-winter conditions, the students are hopeful it will return once the wet season returns.
The greatest success of the previous work conducted has been the native casuarinas planted, with over 200 trees planted and after 151 field days a survival rate of 81%. The casuarinas have not just survived, they are currently thriving with an average planting height of 11cm ± 0.2cm and after 151 field days an average height of 39cm ± 1cm.
Due to revegetation time scale over the large site other methods to achieve similar results were investigated. The Civil Engineering students opted for a ‘Fast Fix’ of installed wind fences to disturb the high winds experienced on site up to 12m/s at the ground surface. 100m of temporary fencing was installed on site with 50% shading cloth installed to reduce wind speed, within a 3 days the wind fence had failed. A combination of gusts up to 13m/s, heavy rain increasing pore water pressure and reducing soil strength is the suspected cause. The wind fence was re-erected and as of project close it has been standing for 8 days.
This project will continue in a reduced capacity with ongoing monitoring of sand Aeolian transportation across the site. The students remain engaged and eager to solve/reduce the issue which some have been working on over 1 year now.