Tweed Heads Mind Map

Tweed Heads Mind Map

1. History

   • First used in the 1800s to open up trade and for settlement
   • Navigation of the river has historically been very dangerous
     • Many capsized boats attempting to access the entrance
   • Training walls constructed in the late 1890s
     • Controlling sand movement and improving navigation
     • Extended by 380m in the early 1960s
       • The extension only improved navigation temporarily
         • The problem
           • The natural longshore drift (travelling north along Leticia Spit) was being trapped behind the southern wall
             • The drift was unable to cross the Tweed River entrance bar and nourish the southern GC beaches

2. TRESBP (Tweed River Entrance Sand Bypassing Project)

   • A project located on the border of NSW and QLD
     • Falls into the jurisdiction of GC city council and the Tweed Shire council
     • The catchment for the river is approximately 1000km2.
   • The river flows through the regional centre of Murwillumbah and extensive estuarine wetlands before flowing out through the trained entrance.
   • The catchment drains the remnants of a volcanic caldera (a large crater). The volcano has been inactive for many years
     • Mt Warning remains as the dominant volcanic plug

3. Issues

   • Sand began to build up behind the southern wall
     • Once the sand had built up to the end of the southern wall it began flowing around and into the entrance
       • The sand just recreated the bar that had be a navigational hazard in the past
   • The beaches on the southern Gold Coast, including Rainbow Bay, Greenmount, Coolangatta and Kirra, are some of the most visited in Australia.
     • Important for tourism industry
       • Beaches are aesthetically pleasing
       • Recreation: beach cricket, swimming and surfing
       • Provides money for the local economy
     • Sandy beaches also provide a buffer of sand
       • Prevents extreme erosion from damaging high rise buildings, roads and other infrastructure that have been built in close proximity to the shoreline

4. Attempts to resolve the issues

   • After the 1967 cyclone, seawalls were constructed along the coastline
     • Sand was periodically dredged from the sand reserve that was building up behind the southern training wall
       • Artificially nourished the beaches and provided protection to infrastructure and other assets
   • In 1974-75 a total of 760000 cubic metres of sand was dredged from the TR entrance and deposited on Kirra beach
     • Expensive, costing over $1 million and was not seen as a permanent solution

5. Solutions

   • TRESBP was implemented in two stages
     • Stage 1
       • Involved dredging sand from the TR entrance and then the direct deposition of the sand on the southern GC beaches
         • In 1995-96 and 1998, 3 million cubic metres of sand was dredged from the TR entrance and deposited on the southern GC beaches
     • Stage 2
       • The installation of a permanent bypassing system, designed, constructed and operated by a private compamny
         • Commenced on the 4th of May 2001

6. Facts and Figures

   • Between 200000 cubic metres and 1 Million cubic metres of sand can be transported along Letitia Spit in any year
     • The sand starts in mid-northern NSW and flows north, parallel to the coastline, before slipping into deep water, north of Fraser Island QLD
   • Tweed Sand Bypassing consists of a jetty and floating dredge
     • Designed to collect sand from the Letitia Spit
   • The jetty is 450m long and supports 10 submersible jets (the jets collect the sand).
     • The pumps don't 'suck' sand from the ocean bed or out of the river, but collect the sand from the longhsore drift
   • The jetty is unable to collect all the sand along Letitia Spit
     • The sand moves into the Tween River Entrance
   • The sand that ends up in the entrance moves across the bar and forms sand shoals offshore of Duranbah and Point Danger

7. Stakeholders

   • These groups or individuals manage the coastline depending on their point of interest
     • Recreational Fishermen
     • Tourism operators
     • Swimmers
     • Surfers

8. Definitions

   • Trained Entrance
     • River entrances trained by breakwater to fix their location and ensure navigability. They also assist in mitigating (making it less severe) floods.
   • Catchment
     • The area drained by a river or water body. Aka river basin

9. The periodic dredging still occurs on the Gold Coast. In July 2017, whale researchers and tourism operators believed the arrival of a giant dredge off the Gold Coast was scaring off migrating humpback whales.