TAS- Tamar River

The Tamar River One of Australia’s largest and most altered estuaries is also a natural wonder The 70 km long Tamar Estuary is a drowned valley formed during a faulting event in prehistory. Tectonic, volcanic and glacial activities have continued to shape this flooded ‘crack’ in the earth into what we see today. The Estuary receives three major river systems: the South Esk; the North Esk; and the Meander. These three main catchments form a large drainage basin, which covers approximately 18% of Tasmania’s land mass. The Tamar is no thready little estuary with a blocked outlet to the sea. It is one of Australia’s major rivers. The water depth of the Tamar estuary ranges from 3 metres at Launceston to over 60 metres. The tide rips through the estuary and creates carved channels, ledges, rocky outcrops and even whirlpools. Near the heads, clean ocean water bathes rich seaweed beds. As you proceed upriver the waters gradually become siltier and darker. Each area creates a unique habitat for a variety of life. History The area around the Tamar Estuary was occupied by various bands of Aboriginal people, who were later called ‘The Northern Midlands Tribe’ by Europeans. Unfortunately little about their life was recorded by early settlers, making their surviving cultural sites all the more important. The population of perhaps 500 people seemed to be mostly based around George Town opening to the sea. They gathered molluscs from the sea and also hunted around inland swamps. A small European agricultural settlement started at the beginning of the eighteenth century and struggled to grow enough food in a valley often noted for unreliable permanent water and poor soil. Only the alluvial plains at the upper end of the river (Launceston) supported reliable crop harvests. For much of the 19th century the Tamar Valley was largely woodland. However, before the days of macadamised roads and cars, the sea was a highway. The Tamar snaked through the wooded hills and connected the world to the settlement at Launceston, a gateway to the rich alluvial soils of the Norfolk Plains hinterland. Isolated farms and small settlements supplied a growing wool industry based on a rough road system and the small Launceston wharves. There were flour mills in both the Supply River and at Windermere, and lime works at Middle Arm. By the end of the century, little farms had sprung had up along the riverside, served by small sailing ketches and river steamers. The access to easy timber stands started an extensive shipbuilding industry from at least the 1830s, mostly building small river ketches. The building of the railway system in the 1860s gave Launceston a geographic advantage, placing it at the junction of three rail routes. Access to water, electricity, rail and sea sparked off heavy industry including precision engineering, brickworks, textile mills and a tin smelter. Regular gold shipments from the Beaconsfield gold mine also lined the pockets of Victorian era investors. They spent their profits on the elegant commercial buildings and leafy parks that are still a feature of Launceston’s CBD today. They also improved the wharves and started blasting and dredging the many obstacles in the river estuary. These rocks and tidal flats made a sea journey up the Tamar a potentially dangerous undertaking. Gradually the trees were cleared and the rivers choked with sediment and industrial effluent. Choking the river with mud further hampered 18 shipping and massive works filled in mud flats and reshaped the riverbanks. As prosperity grew there was also time for leisure. The river supplied opportunities for fishing, hunting, sailing and picnicking. On public holidays, industrial workers crammed into the river’s steam ferries. In a time when no-one had cars, over 1000 people a day would go by steamer from Launceston to Beauty Point and George Town. Today tourists still carry out these rituals, but only on short hops around the city sights. Now the car is king. The Tamar Today The Tamar Region is now home to over one quarter of the Tasmanian population with the combined population of the Launceston, George Town and West Tamar municipalities being in excess of 92 000 residents. The shipping and industry has moved down river to Bell Bay and the rail services have shrunk, but the Tamar Region is still the Northern Tasmanian centre for industry and commercial activity. Forestry has waned and the industrial plant, now located near George Town at the river mouth, faces an uncertain future. At the other end of the estuary tourism, education services, specialty food processing and other services are taking over as new industries for the region. While many things change, others remain the same. The major land use in the region is still grazing. Other major land uses include forestry and viticulture. The clearing of native vegetation and development has led to a loss of biodiversity. Remaining bush is often under pressure from fire, overgrazing, wood cutting and weeds. However, a large amount of what remains is now protected in conservation reserves. Despite an active industrial history the Tamar Region is still quite ‘natural’, including retaining in excess of 65% of its vegetation cover. Its feeders rivers, creeks and streams don’t always run clear thanks to sediments (some of which is natural), but it is mostly clean. Water quality and stream condition tests in 2005 found these systems are generally in good condition, although some areas are still experiencing high levels of turbidity and pollutants. Despite interference from humans the Tamar estuary is intact enough for it to be considered a class A estuary in terms of its biological significance. The Tamar estuary was a problematic inclusion as a Class A estuary. It got the guernsey largely because it is the only estuary of its type in Tasmania (mesotidal drowned river valley – estuaries with wide river mouths, rocky headlands and deep channels). However it still possesses extremely high plant, invertebrate and fish diversity, and a large component of species not recorded elsewhere. Biodiversity Hotspots Low Head The eastern outlet of the Tamar Estuary at Low Head has been identified as a significant waterbird habitat with high scenic qualities. The Tamar River Mouth Reserve contains saltmarsh flats and coastal vegetation important to waterfowl. Seals, dolphins and whales are fairly regular visitors. There is a major penguin viewing platform at Low Head. In sampling done recently of marine fauna, Low Head sites ‘scooped the pool’ and possessed substantially higher species richness than most other sites, with 116 species collected at Low Head compared to 71 at the next richest site (Welcome Inlet). 19 There are rich seagrass beds (Heterozostera, Posidonia and Amphibolis seagrass) near the estuary mouth, a habitat that possesses extremely high biodiversity, including numerous species not protected elsewhere. A marine protected area has been proposed here. Fishermen wanted a limited area from Low Head to Dotterel Point. Environmentalists also wanted to add the seagrass beds in Lagoon Bay extending 500m offshore for a distance of 3 km along the coast from Low Head to She Oak Point, including unusual deepwater habitats off Barrel Rock. This debate is yet to be resolved. Barrel Rock and Farewell Beacon The rock lies near the Low Head lighthouse and has been a shipping obstruction since the early days of settlement. It was once marked by an old barrel-shaped buoy. This has been replaced by a steel marker with a fish-shaped weather vane on the top. Therefore the rock is known as both Barrel Rock and the Fish Beacon. Because of the strong tide, the rock is covered in filter feeding marine life. The reef structures, both natural and man-made, have attracted a lot of fish. Although the bottom is fairly muddy the dive is still very colourful with a vast array of interesting sponges to look at and photograph. The area around the Farewell Beacon has even more fishlife. Straight out from the Low Head Lighthouse there are also some large reefs that are often covered in luxuriant growths of Kelp. Hebe Reef Another area which is often visited by divers is Hebe Reef. This reef offshore of the heads sits almost in the centre of the shipping lanes and thus has claimed many vessels. One of these is the Barque “Eden Holme”. The “Eden Holme” was on a voyage from London loaded with general cargo for Launceston. On the 5th of January 1907, Captain Dulling asked for a pilot to enter Tamar Heads. The “Eden Holme” was under the command of Pilot Mullay when the wind dropped away and the vessel was becalmed. Without the power of the wind she drifted slowly onto Hebe Reef and bumped lightly. Although the barque was undamaged the tide was falling. Soon the vessel began to groan under her own weight and eventually the plates gave way. By the time a tug arrived it was too late to save her. She lay intact on the reef for some time and was heavily salvaged before finally breaking up. The vessel was owned by the famous company of Hine Brothers. The “Eden Holme” rests in a depression in the rocks and the hull plates above this 20 depression have been broken off and scattered. Much of the cargo was salvaged, but divers can still find fragments of glass, china and shot. Deadeyes, full bottles of wine and vinegar bottles have also been located in the past. Divers mostly stay in the shallows where there are wrecks, but apparently the deeper areas of the reef also offer very high fish species biodiversity. Rocky crevices are home to invertebrate life and the reef is covered in seaweed. The Hebe Reef is still a menace. In 1995 the Iron Baron went up on the rocks and spilled oil into the river. After several years, fortunately the marine life recovered. Tamar fish life Everyone loves fish and many of us love fishing. The river still offers good fish populations, thanks probably to the regions low human population, the constant streams of pelagic fish coming in from the ocean, and some sound management. The Tamar is a Shark Refuge Area, protecting the river as a nursery for Gummy Shark, stingrays and seven gill sharks. Bottom dwelling sharks and rays are still plentiful in the Tamar River, where they have been heavily depleted in other urban areas. They seem to love the muddy ooze even in the upper reaches and Gummy sharks can be seen as far up as Rosevears. The deeper sections of the river between Windermere and the Heads have better fish life. In the darker sections of the river Rock Cod, Ling, Gurnard are common in the rocky crevices. The shallower sand and mud flats are home to Flathead, Flounder, Mullet, Whiting and Garfish. Mullet may be caught up the river as far as Windermere. Garfish seldom venture past Swan Point. Whiting prefer the clearer sea grass beds closer to the river mouth. Leather Jackets, trevally, luderick, wrasse, Magpie Perch, boarfish, sweep and many other fish species cluster around any rocky reef or structures such as channel markers, piles, reefs, breakwaters and headlands. Australian Salmon, Mackerel, Pike, Couta, Snapper, Kingfish, Bream and Snotty Trevally move in and out of the Estuary on a seasonal basis. Schools chase bait fish around the mouth of the river and as far up the river as Egg Island. While we often focus on the species in the river that we fish, but by far the greatest number of species are the tiny ones that are often hard to see. The mud and sand is also home to countless gobies and blennies and other weird and cryptic fish species like Warty Prowfish. The Tamar Goby is actually common in SE Australia, but was first described here. Males grow to a larger size than females and have larger mouths, and very bulbous cheeks. They are small and can be seen scuttling along the sand in the shallows. Tamar Goby, Afurcagobius tamarensis. Source: Rudie H. Kuiter 21 The hardiest of all fishes are perhaps the eels found in the upper reaches. They spawn in freshwater streams and then make for the sea, adapting to the rising salinity as they head downriver. These days they often find natural watercourses blocked by dams and low water levels, but they can wriggle out on to the grass at night to get around them. This species has been re-stocked upstream of the Trevallyn Dam when its former distribution was blocked by the large dam wall. Eel ladders have now been installed on the dam face. The young eels, the elver, are eaten by all sorts of birds, sea eagles, herons and cormorants. Their poisonous skin coatings sometimes deter predators. They settle onto the muddy bottom of the upper estuary as far up as Cataract Gorge and live on small fish and insects. Here pollution can often make the water rich in bacteria that then depletes the oxygen. Recently, a spell of warm weather caused quite a few to die of stress and float to the surface. Tamar Island Wetlands Reserve The area from the Tamar Island Wetlands Reserve to the Batman Bridge is part of the Tamar River Wildlife Sanctuary. It is identified as an important area. From here 43 local and 21 vagrant bird species have been sighted. It used to be open to the tide, but dozens of disused vessel were scuttled at either end of the mudflats to divert the tide and allow more sediment to settle there. Now it is covered in marshy vegetation and nutrient rich mudflats, in some ways replacing tidal flats that have been lost in other parts of the river. A wooden platform and a visitor centre make it a great recreational site within easy reach of the city of Launceston. The dredge “Ponrabbel” is a visible symbol of the changes that have occurred in the estuary. She was bought during the First World War to dredge the channel near Launceston to facilitate shipping access. Today she is abandoned, used at the end of her life as a training wall to block off the tidal flows around the Tamar Island mudflats. Ironically, she is slowly disappearing into the choking the mud that she spent her life trying to keep at bay. As the industrial past literally sinks into the background the tidal flats are now a major bird wetland. Problems of a Developed Landscape While Low Head is flushed by ocean currents and is a very rich marine environment, it’s a mixed result overall. Some areas are not in great shape with Paper Beach dominated by species typical of heavily disturbed areas. The estuary is severely impacted by introduced species including ricegrass Spartina anglica, East Asian bag mussel Musculista senhousia and pacific oysters Crassostrea gigas. They are hard to manage simply by creating a reserve on paper, but more concrete efforts have followed with ricegrass and gambusia control programs enjoying success. Pollution isn’t the major issue thanks to extensive programs to treat sewerage and industrial effluent. The stormwater drains still have a coat 22 of slimy algae around them, but the pollution is typical of a populated area along a narrow waterway. The Tamar River Recovery Plan is aimed at further improving the health & amenity of the Tamar River Estuary by removing and reducing the inputs of sediments and nutrients from the combined sewage and stormwater overflows and other areas of the catchment. Launceston has an usual drainage system where stormwater flows into sewerage pipes. It’s hardly desirable, but it only causes overflows when the river is in flood and the sewerage is heavily diluted. The cost of replacing the entire drainage system is currently prohibitive. Many of the Tamar’s pollution issues are legacies of past bad practice. In the industrial era there were few controls and highly persistent pollutants like heavy metals were dumped into the river. Things are on the mend. Cod, flounder, flathead and mullet were collected recently and analysed for metal concentrations. Concentrations in fish were below the FSANZ standard and not considered to be of concern to public health. It is still recommended that fishers limit fish servings from the Tamar River estuary to 2-3 serves per week. However oysters showed significant levels of copper, zinc and cadmium and are considered unsafe for people to eat. Mud, Inglorious Mud Most of the chatter about the river focusses rightly or wrongly on one issue. Siltation of the upper Tamar River has long been an issue and has caused annoyance to local water users with narrowing shipping channels and smelly mudbanks blocking boat ramps and jetties. Dredging activities have been undertaken there since as early as 1859, a program that has now continued for almost 150 years. It has been estimated that just in the period from 1947 to 1966 alone, about 255,000 tonnes of silt were removed annually from the area between the top end of Home Reach and Stephensons Bend. This amounts to 360 tonnes per tidal cycle to maintain the depth of the river channel. It was never enough to ‘fix’ the issue. In a report to the Marine Board of Launceston in November 1899, Mr C. Napier Bell noted that gains made tended to be lost in a very short time. Since the mid-1960s, when a major deep-water port was established at Bell Bay, dredging activities in the wider river have been more intermittent, with most effort concentrating on maintaining water depths alongside Kings Wharf at Inveresk. As ships no longer berth at Launceston, the dredging in the upper reaches slowed. Space for spoil dumping was used up and costs increased dramatically relative to the small commercial gains to be made from dredging. A study from the 1980s suggested spilling water from Trevallyn Power Station in phase with the tides and using silt traps instead. The Tamar Siltation Study in 1986 found that the build-up of sediment in the upper Tamar River was controlled by two major factors. Essentially, major flood flows from the two rivers flush the sediments from the upper Tamar (through scouring) down into the lower reaches of the estuary, while the tidal mechanism acts to return this sediment during periods of low river flows. The main cause of the mudflats in the upper Tamar are natural processes related to the tide and flood patterns. Sediment flows into the Tamar River are considered fairly low for such a large watershed. Damming has caused a drop in river flows which has also slowed down the scouring of Home Reach in the upper estuary, but in some ways this has just been to the benefit of the lower estuary. The river at Launceston was always a narrow-channeled mudflat. In many ways the Tamar is simply returning to its ‘natural’ condition. The issue is still very sensitive for river users, and intermittent dredging is likely to continue. “The silt seriously destroys the amenity of the river, it doesn’t look the best at low tide, it seriously limits the efforts of rowing clubs and sailing clubs and (is bad) for tourists,” a local told “The Examiner” newspaper. The silt is also significant not just as an inconvenient eyesore, but also because it can act as a trap for heavy metals including high levels of zinc, chromium, lead and cadmium. In 1993 it was found that 30-50% of all the dredged mud doesn’t meet health guidelines for use as landfill due to zinc, lead and cadmium. Chromium was above the accepted limits in all of the samples. The cadium is especially unstable and likely to leach out of any soil made up from old dredging spoil. These are a legacy of the Tamar catchment’s history of mining and heavy industry. This is especially so in the Upper Tamar and no shellfish should be eaten from the estuary. 23 Raking To kick off the new approach, 2.5 cumecs of released water from Trevallyn Dam was promised by Hydro. Someone then came up with the idea of raking the mud while the river was in flood to keep it moving away from the city. The Federal government threw in $5 million for silt ‘reduction’. In 2013 the program removed 240,000 m3 and then 101,330 m3 of sediment in 2014 from the Upper Tamar (Yacht Basin) and North Esk Rivers (in the vicinity of Seaport). Sediment raking targets high flows or is centred around the full moon tide and each campaign will rake for 10 days or nights on each ebb (outgoing) tide. The raking used existing fishing vessels and has been a cheap way of moving the mud elsewhere, perhaps further down river where it might create fresh issues. The Flood Authority commenced a Sediment Tracing Program in order to better understand sediment behaviour in the Tamar Estuary. The program involved the placement of a non-harmful tracing medium in the mudflats around North Bank. Bathymetric surveying of the river is also ongoing and to provide information on where the displaced sediment settles. New Development The Tamar Valley is an area of slow economic growth that needs new industries and new ideas. Some of these ideas are related to low key ‘green, clean’ industries and others are ‘bigger’ and a bit more based around traditional industries. A plan for a huge wood pulp mill on the West Tamar attracted massive protests, and was eventually sunk by a combination of financial and political difficulties. Another idea that is both radical and quite traditional is the idea for creating a Tamar Lake. A not-for-profit association has privately funded the investigation of the technical, environmental and economic feasibility of installing a barrage on the Tamar River at Point Rapid, just south of the Bell Bay Port. The $320 million project would create a 60- kilometre-long lake that extends upriver to the city of Launceston at the Cataract Gorge. Tamar Lake would supply freshwater for residential, industrial and agricultural developments throughout the valley. Proponents say the lake would be a permanent solution to the problem of silt accumulation in the Tamar River by apparently ending the asymmetrical tidal action that remobilises silt on the high tide. There are several issues to work through. It is admitted that “the key to the proposal would be TasWater carrying out its strategy to stop sewage flowing into the estuary”. That would mean massive additional works to Launceston’s drainage systems. The water table level in the low-lying suburb of Invermay would also have to be managed at a constant level by controlling the lake level. The studies state that the barrage will not negatively affect flood levels in Launceston.The environmental impact assessments apparently also states that “while there will be some displacement of natural ecological values, no listed species will be threatened and the freshwater habitats (including the Tamar Island Wetlands) will be greatly expanded”. “The only species to die will be the imported rice grass”. However, other material from the proponents also states that, “Migratory wader species may suffer displacement due to loss of intertidal zones – habitats will need management while they adapt.” With a permanent mid to high- tide water level, “…tourism and aquatic sports are obvious beneficiaries with 24-hour navigation for pleasure and tourist vessels from their berths in Launceston downstream to Low Head and passage through a lock in the barrage”. Its certainly a novel idea and what a sum to raise when its added to the drainage upgrade costs. I’m yet to be convinced that it will work either practically or environmentally, but keep those ideas coming. I have a suspicion that less capital-intensive and controversial proposals will form a larger part of the region’s economic future.