Senior Student Booklet Version 7 1 Upper Nerang Catchment Land Use Pollution Source Notes Impact Contaminants Nutrients Sedimentation + + + - 0 - - - stream - Fuels/Oils Chemicals Debris Nitrate Phosphate Clearing Compaction Runoff Erosion bank, gully, in Numinbah Valley EEC National Park Roads & Bridges Residential Agriculture: horse/cattle Correctional Facility Tourism - Recreation Tourism - Accom. 3 Geological and Geomorphological History of the Region The Gold Coast hinterland is on the Indo-Australian crustal plate which is moving 7cm north each year. The Gold Coast hinterland was over a ‘hot spot’ between 24 - 23 million years ago. Hot spots are weaknesses in the Earth’s crust that periodically force basaltic magma to the surface and erupt to form broad volcanoes. Two large volcanoes were created at that time; the Focal Peak Volcano near Mount Barney, and the Tweed Volcano. The Tweed Volcano area stretched north to south from Tamborine (QLD) to Lismore (NSW), and west to east from Mt Lindesay (QLD) to 14 kilometres off the east coast. The Tweed Volcano built up broad, shield-shaped mountains (approximately 100km in diameter) predominantly from great piles of highly fluid basalt lava that flowed long distances. Towards the end of their activity, the magma deep below distilled into other types of lava, mainly rhyolite. The viscous (sticky) rhyolite erupted explosively and plugged vents on the northeastern flank of the shield volcano. The rhyolite flows covered a much more limited area than the basalt flows. Some rhyolite magma formed tall bodies of rock that can still be seen today as Egg Rock and Page’s Pinacle. The central summit of the Tweed Volcano was located over the present Mount Warning and is estimated to have reached about 2000m above sea level (Mt Warning is 1156m above sea level). After the Tweed Volcano became extinct 10 million years ago, the tall mountain attracted heavy rainfall (orographic rain). The igneous rock gradually weathered to form rich soils that supported thick rainforests and many streams began to flow from the peak. The streams slowly cut deep gorges into the sides of the mountain (erosion), and over time the gorges widened into valleys. 4 1 2 3 Figure 1. Progressive Erosion of the Tweed Volcano (vertical scale exaggerated) Erosion of the Tweed Volcano has occurred in part due to the streams radiating out from it: Tallebudgera Ck and Currumbin Ck (east); Nerang R, Coomera R, and Canungra R (north); and Albert R, Christmas Ck, and Running Ck (north, north-west). Erosion is occurring at an average .03mm/year (6.9km2 in 10 million years). The Tweed R has eroded the headwaters of the Nerang R and will continue to remove material. Most erosion occurs in the valleys. The ridges of the volcano are now flat plateaus and include Mt Tamborine and Beechmont. The streams on the eastern side of the volcano are more active because they receive increased rainfall (orographic rain). The Tweed Valley is now an erosion caldera with only the remnant plug of the volcano, Mt Warning, remaining. 5 History of Numinbah Valley Figure 2: History of Numinbah Valley For thousands of years prior to the European settlement, the Aborigines freely roamed Nerang River Valley and the adjacent land. The Kombumerri People visited the Numinbah Valley and the high plateau in summer searching for and gathering food and medicines. In winter they moved closer to the coast, gathering fish and seafood. In Bushranger’s Cave, Aboriginal artifacts have been discovered by the Anthropology Department of the University of Queensland and these have been estimated to be 10,000 years old. The original forests of the Numinbah Valley were thick, lush rainforests or towering schlerophyll forests in the drier sections. The lowland sub-tropical rainforest was extremely rich in biodiversity and these towering giant trees attracted the pioneering wood cutters in the 1860s. Red Cedar, Hoop Pine, Silky Oak, Crow’s Ash, Black Bean and Booyongs promised wealth to these early loggers. For the next 100 years, the woodcutter’s axe dominated the landscape as the valley was stripped of its timber with the clearing often reaching high up into the hills. Five sawmills were kept busy supporting this industry. Farming, mainly dairying, beef cattle, pig raising and banana plantations became the main industries after the land was cleared. In recent times, tourist visitation in the area has increased. Notes: 6 Stop 1 – Border Gate The Border Gate is in the vicinity of the headwaters of the Nerang River. From this site you can see the source where it begins as two tiny streams which tumble down the steep slopes of Mt Hobwee before joining together to flow through the farmland, over rapids and waterfalls, and through the narrow V- shaped valley. Clearing of the land high up into the hills is very obvious at this point. By observing closely you will note there is slumping of the soil on the steep slopes, dead trees, lack of vegetation protecting the river, and evidence of landslides. In the past, the lack of trees to hold the soil together on the steep slopes, combined with regular rainfall have caused large landslides that have washed a lot of sediment into the river. Maintaining water quality is essential for the health of the catchment. Yet even at the start of the catchment, people have begun to pollute the river. Pollution enters the river in three forms: nutrient pollution, other contaminants, and sedimentation. Even small increases of these can have a detrimental effect on delicate freshwater ecosystems. Weeds Weeds are a widespread problem in Numinbah Valley. Invasive weeds quickly establish themselves in cleared areas. Weeds can spread in a variety of ways: wind and water, livestock, birds, vehicles, and people (such as dumping garden waste). Weeds restrict the growth of native plants, provide limited habitat for wildlife, and contribute to poor soil stability. Weed management and removal costs the Queensland economy $600 million per year. Species such as Parthenium and Lantana have an impact on human health and many species are toxic to cattle. Control Description Example Measure The use of legislation, quarantine and Limits on the species that can be Prevention education to prevent the introduction of sold. Fines for illegally dumping weeds. garden waste. Machinery – appropriate for large accessible areas Physical The use of machinery or removal by hand. Hand – sensitive environments Removal where minimal disruption is important Use of targeted herbicides which kill the Foliar spray is effective for large weed. Herbicides can be delivered by foliar Chemical areas of lantana. Must be followed spray, paint, or injection. Cost effective but Control by revegetation or large-scale may have unintended environmental erosion will result. impacts. Use of insects or pathogens (diseases) that affect the health of the weed. Usually found Lantana Beetle - since 1914, 31 in country of origin. Strict measures are in agents have been introduced to Biological place to minimise negative effects on native control lantana. Some have been Control species. effective. e.g. Sap-sucking bug Biological control rarely gets rid of weeds Teleanemia scrupulosa but can control growth and spread. Table 1: Information on control measures for weeds. 7 1. Suggest some strategies that could be used to prevent sedimentation in Numinbah Valley from slumping, landslides, and erosion. Turn to River Assessment Data Sheet and Sources of Pollution Sheet Complete Field Sketch on page 17 Stop 2 - Natural Bridge The sub-tropical rainforest at Natural Bridge remains largely unchanged over the last 100 million years since Australia was part of Gondwana. Natural Bridge has been named as a national geological feature and is a World Heritage Listed site. The area was set aside as a Recreational and Scenic Reserve in 1892 and managed by the Forestry Department until it became a National Park in 1959. Cave Creek runs through Natural Bridge and then joins the Nerang River. It is an example of a pristine environment due to minimal human impacts. The banks of the creek are forested, providing filtration of runoff and stabilisation of the sediments. Dense growth stabilises soil and shades water. Aquatic and terrestrial fauna have habitat in the vegetation. Natural Bridge is home to rare and endangered species including Fine Leaved Tuckeroos, Red Cedars, Angle-headed Dragons, the Paradise Rifle Bird, the Richmond Birdwing butterfly, and the largest glow worm colony in Australia (Hall, 1990). Without careful management, this area could easily be damaged. Natural Bridge has an extremely high visitation rate both during the day and at night. People visit the site for its natural beauty, unique geological structures, and the glowworms. National Parks maintain the site and closely monitors visitor numbers to ensure a minimal impact. National Park Rangers have installed fencing, removed picnic tables, banned swimming, and limited tour group size in order to protect the area. 2. Despite the undisturbed environment at Natural Bridge, contamination of the waterway could have already occurred. Explain how this might happen. 3. Outline some measures taken by National Parks to minimise / manage the impacts of visitors to this site. Turn to River Assessment Data Sheet and Sources of Pollution Sheet 8 Stop 3 – Bochow Park There is a large perlite mine near Bochow Park that was established in 1953. Perlite is a volcanic rock that is mined to produce a light-weight concrete aggregate for fire proofing, insulation, a hydroponic medium, paint filler, and for use in potting mix. Queensland is the only state in Australia that is mining perlite. The Park is run by the Gold Coast City Council and provides rubbish bins, gas BBQs, a playground, and open grassy areas for recreation that are mowed regularly. 4. What type of impacts could a mine be capable of causing on the area? 5.