Project Description
Pipelines and subsea structures can cause significant and rapid sediment scour when deployed on mobile seabeds. This results in the need for frequent and costly inspections to assess reliability and serviceability. Typical scour mitigation solutions include dumping of gravel, rocks, sandbags and gabions in the scour holes and eroded areas around pipelines; however, by creating sharp gradients in near-bed sediment transport, these approaches can also cause additional scour around their edges which ultimately impacts negatively on the longevity and effectiveness of these approaches.
The aim of this research was to investigate the performance and efficiency of artificial seagrass mattresses (ASMs) for scour protection around subsea structures. These nature-based structures have the potential to both trap sediment and reduce bed shear stress, thereby presenting a long-term solution for seabed stabilisation. Our preliminary results revealed that seagrass shoot density and flexibility have a significant impact on the rate of sediment capture. The ultimate goal of this project was to develop design guidelines and implement performance prediction for the use of ASMs in a wide range of field applications (from offshore projects to coastal defence schemes, seagrass rehabilitation and riverbank protection).
Figure 1. Artificial Seagrass mats (ASMs) are efficient in capturing sediments and this efficiency increases with mat shoot density (Courtesy Hannah dawn). (a) Start of test, (b) low-density ASM, (c) high-density ASM