7.6 The Tweed River Entrance Sand Bypassing Project

1. it became necessary to extend the tweed river breakwaters due to further sand build-up at the entrance of the heads.

2. The breakwater on the southern side of the tweed river acted to trap sand that would naturally be moved in a northerly direction by longshore-drift. The continual build-up of sand on the southern side of the breakwater eventually caused the river mouth to once again silt up.

3. The dredging of the sand at the mouth of the Tweed River was trucked and moved to the gold coast for beach nourishment. This is an expensive solution and one that would need to occur continually in order to maintain the sand supply to the beaches. The removal of the sand is essential for the ships to be able to get through the tweed river mouth. The natural process that causes sandbars to form is silting.

4. The dredging of the tweed river mouth and associated beach nourishment program was only a short term solution as the silting of sand at the mouth of the tweed river is an ongoing process and this management strategy is just not effective long-term.

5. The TRESBP replaces the natural process known as longshore drift in the construction of breakwaters. This construction breaks the drift of the ocean when it hits the beach as it cannot go past the wall of rock.

6. I believe the TRESBP is one of the most successful projects in Australia for a few reasons. Firstly because the intended aim of the project was to stop silting at the mouth of the Tweed River and to stop the formation of a sand bar. The construction of breakwaters was the best thing that could have been done and did work in stopping the silting – temporarily. Even though it is very costly this project can be used as a learning curve for future projects. It gives developers an idea on what they should do the future, which may be even more beneficial and less costly. I’d say as a whole the TRESBP was very successful.

7.  –

8. 1962 – you can see that the Tweed River entrance is extremely vulnerable to the build up of sand known as silting and something needs to be done.

1969 – The construction of the breakwaters has opened the Tweed River heads and caused the beach to shift position. There is more sand on the surrounding beaches as the process of dredging has also taken place.

1994 – The breakwaters haven’t really changed but the amount of sand on the surrounding beaches has increased dramatically. Fairly soon a new solution will need to be put in place as the sand will reach the edge of the breakwater and will once again, begin to form a sandbar.

9. In the topographic map the length of the breakwater is approximately 350 metres in 1994. In 1962 the breakwater was not present.