Tweed Heads Mind Map

History
1. First used in the 1800s to open up trade and for settlement
2. Navigation of the river has historically been very dangerous
  1. Many capsized boats attempting to access the entrance
3. Training walls constructed in the late 1890s
  1. Controlling sand movement and improving navigation
  2. Extended by 380m in the early 1960s
    1. The extension only improved navigation temporarily
      1. 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
TRESBP (Tweed River Entrance Sand Bypassing Project)
1. A project located on the border of NSW and QLD
  1. Falls into the jurisdiction of GC city council and the Tweed Shire council
  2. The catchment for the river is approximately 1000km2.
2. The river flows through the regional centre of Murwillumbah and extensive estuarine wetlands before flowing out through the trained entrance.
3. The catchment drains the remnants of a volcanic caldera (a large crater). The volcano has been inactive for many years
  1. Mt Warning remains as the dominant volcanic plug
Issues
1. Sand began to build up behind the southern wall
  1. Once the sand had built up to the end of the southern wall it began flowing around and into the entrance
    1. The sand just recreated the bar that had be a navigational hazard in the past
2. The beaches on the southern Gold Coast, including Rainbow Bay, Greenmount, Coolangatta and Kirra, are some of the most visited in Australia.
  1. Important for tourism industry
    1. Beaches are aesthetically pleasing
    2. Recreation: beach cricket, swimming and surfing
    3. Provides money for the local economy
  2. Sandy beaches also provide a buffer of sand
    1. Prevents extreme erosion from damaging high rise buildings, roads and other infrastructure that have been built in close proximity to the shoreline
Attempts to resolve the issues
1. After the 1967 cyclone, seawalls were constructed along the coastline
  1. Sand was periodically dredged from the sand reserve that was building up behind the southern training wall
    1. Artificially nourished the beaches and provided protection to infrastructure and other assets
2. In 1974-75 a total of 760000 cubic metres of sand was dredged from the TR entrance and deposited on Kirra beach
  1. Expensive, costing over $1 million and was not seen as a permanent solution
Solutions
1. TRESBP was implemented in two stages
  1. Stage 1
    1. Involved dredging sand from the TR entrance and then the direct deposition of the sand on the southern GC beaches
      1. In 1995-96 and 1998, 3 million cubic metres of sand was dredged from the TR entrance and deposited on the southern GC beaches
  2. Stage 2
    1. The installation of a permanent bypassing system, designed, constructed and operated by a private compamny
      1. Commenced on the 4th of May 2001
Facts and Figures
1. Between 200000 cubic metres and 1 Million cubic metres of sand can be transported along Letitia Spit in any year
  1. The sand starts in mid-northern NSW and flows north, parallel to the coastline, before slipping into deep water, north of Fraser Island QLD
2. Tweed Sand Bypassing consists of a jetty and floating dredge
  1. Designed to collect sand from the Letitia Spit
3. The jetty is 450m long and supports 10 submersible jets (the jets collect the sand).
  1. The pumps don't 'suck' sand from the ocean bed or out of the river, but collect the sand from the longhsore drift
4. The jetty is unable to collect all the sand along Letitia Spit
  1. The sand moves into the Tween River Entrance
5. The sand that ends up in the entrance moves across the bar and forms sand shoals offshore of Duranbah and Point Danger
Stakeholders
1. These groups or individuals manage the coastline depending on their point of interest
  1. Recreational Fishermen
  2. Tourism operators
  3. Swimmers
  4. Surfers
Definitions
1. Trained Entrance
  1. River entrances trained by breakwater to fix their location and ensure navigability. They also assist in mitigating (making it less severe) floods.
2. Catchment
  1. The area drained by a river or water body. Aka river basin
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.

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	Criado por Natasha Nguyen aproximadamente 7 anos atrás