Redundant Weir Removal: The Branch River Crossing - A Case Study THE BRANCH RIVER Other industries that are important to FRESHWATER CROSSING the region include commercial fishing and oyster farming, which are strongly The Project linked to local waterways and rely on a The removal of the Branch River healthy catchment. Crossing is part of a larger weir removal project being undertaken by WWF History Australia, the Environmental Trust of The Branch River Crossing was NSW and NSW Fisheries, with another constructed in 1951 by the Colonial 2 redundant weirs to be removed over Sugar Refinery (CSR) for timber the next 12 months. This project aims to hauling to the mills. At that time a small increase public awareness of the township with a sawmill, school, environmental effects of in-stream several homesteads and a general store barriers. It provides a framework to was located beside the crossing. Fishing facilitate community-based weir was a popular activity for the locals as removal projects and demonstrates the both fresh and saltwater habitats were ecological benefits of improved river available. People also travelled upriver, health. The weir removal framework by boat, from Port Stephens to fish and will assist in the development of similar to take advantage of social occasions projects throughout Australia in the (Anon. 1987). future. Current Use Location The Branch River Crossing is no longer The Branch River Crossing is located used by CSR and is now the near Port Stephens in the Karuah River responsibility of the Great Lakes Catchment, NSW, about 22 km NNE of Council. Land adjacent to the crossing Karuah. The crossing itself is situated is currently used for primary on a natural rock bar at the upper end of production, predominantly stock the tidal limit. Water activities like grazing. A light vehicle bridge 300 m boating and fishing are major upstream provides a river crossing for contributors to the area’s tourism local traffic and heavy vehicle access is industry and local economy. now possible via Booral. “A weir is a structure (including a dam, lock, regulator, barrage or causeway) across a defined watercourse that will pond water, restrict flow or hinder the movement of fish along natural flow paths in normal flow conditions (DLWC, 2001). Habitat now re-opened upstream of the removed crossing on the Branch River. Photo: NSW Fish- eries. Why remove the crossing? breeding and survival of native fish The crossing is acting as a weir across populations throughout NSW. the Branch River. Construction of weirs Removing this crossing also eliminates such as this can detrimentally affect public liability and on-going river structure by: maintenance costs for the Great Lakes • preventing sediment and nutrient Council. from moving along the waterway; • favouring exotic species by THE REMOVAL PROCESS reducing water quality and water Pre-removal surveys Pre-removal surveys were conducted to level variability; establish baseline information on water The Branch River Crossing during flood - note height • preventing native fish from of the structure. Photo: C. Thrupp. quality, fish habitat, fish species, migrating to spawn or expand their terrestrial habitat and riparian habitat; and vegetation. Fish sampling was • preventing the recruitment of native undertaken above and below the fish from other areas, thus resulting crossing using gill nets and fyke nets at in genetic isolation. set points. Catch is shown in table 1. The presence of one or more of these barriers can have a cumulative effect on Stakeholder consultation the abundance of native fish species and NSW Fisheries were the ‘determining may lead to local decline and even authority’ in the removal decision and regional extinction of fish species were responsible for deciding if the (DLWC, 2001). weir removal was going to have a Habitat upstream of the Branch River Crossing. Photo: C. Thrupp. significant, detrimental effect on the Removal of the crossing has re-instated environment. (Hobson 2003). The fish access to upstream habitat. This is Department of Infrastructure, Planning important for fish species that migrate and Natural Resources (DIPNR) also between saltwater and freshwater (or carried out a study and provided vice versa) to complete stages of their comments on the likely biophysical life cycle. Other benefits include impacts of the proposed weir removal. restoration of the natural water flow and Letters were distributed to all non- tidal limit and improved water quality. agency stakeholders, including local Removal of this structure is part of a landholders living around the project strategy to improve the migration, NSW Fisheries collecting data. Photo: C. Thrupp. Table 1. Fish species found in pre-removal surveys Scientific Name Common Name Above Below Weir Weir Ambassis jacksoniensis Port Jackson glassfish 0 237 Anguilla reinhardtii Long-finned eel 5 11 Gerres subfasciatus Silver bellies/ biddies 0 83 Hypseleotris sp. Hypseleotris gudgeons 7 5 Liza argentes Flat-tailed mullet 0 28 Left: Table showing Macquaria novemaculeata Australian bass 13 49 fish found before the survey. Mugil cephalus Bully/Sea mullet 6 10 Right: Excavator re- moving the crossing. Myxus petardi Freshwater mullet 2 1 Photo: C. Thrupp. Philypnodon grandiceps Flat-head gudgeon 71 148 Far right: Australian bass (Macquaria nove- Philypnodon sp. 1 Dwarf flathead gudgeon 3 1 maculeata). Photo: NSW Fisheries. Pseudomugil signifer Blue eye 0 49 site, inviting comment on the proposed Branch River Crossing removal. A break-through Subsequently, there was significant Day 1 An excavator and rock breaker were used to break support from local landholders and through the top of the concrete cap on one side of stakeholders. Their endorsement was the crossing so that the excavator could work back evident during discussions at the time along the crossing. This enabled trucks to reverse of removal and during interviews along the crossing for loading. conducted for the production of a Initial break of the crossing on Day 1. video on the weir removal process. Photo: C. Thrupp. Support from the local landholders and stakeholders contributed to the The waiting game project’s success. Day 1 After breaking away a small section of the cross- Post-removal surveys ing, a 15 hour interval was required to allow water Fish surveys will be conducted by NSW levels to drop to the new height. This minimised Fisheries, in mid 2004, above and below the movement of suspended solids during the re- the removed crossing at the same points moval and exposed the whole structure. used for the pre-removal survey. Allowing for the outflow of water, to reduce upstream water levels late on Discussion Day 1. Photo: C. Thrupp. Native fish such as Australian bass and a number of mullet species are expected to benefit from the crossing removal as Exposed they regularly migrate between fresh Day 2 and saltwater. Recreational anglers will After the crossing was exposed, the excavator was also benefit from improved fish habitat able to break-up the structure and remove the de- and subsequent fishing opportunities bris with the help of 6 tip trucks. All potential is- within the Branch River. sues were considered including the possibility of acid sulfate material within the debris. To minimise any risk, all spoil was taken off-site. Collecting the debris, which was carted off-site to a council landfill. Photo: C. Thrupp. Going….going…. Day 3 The old culverts also needed to be broken-up be- fore being removed. Finally after 3 days of work the removal of the structure was nearly complete. The natural rock bar on which the crossing was originally built remained intact. Toward the final product. Photo C. Thrupp. …Gone… Day 4 A couple of metres of the crossing was left near the edge to help maintain bank stability. The site was then cleaned-up and a clear fish passage re- instated. For the first time in 52 years, high tides are able to flood-out the natural rock bar. Branch River, after the crossing re- moval. Photo: C. Thrupp. Table 2. Approximate budget First published in December 2003 by WWF Every effort was made to ensure for Branch Crossing removal Australia. minimal impact on the environment Activity Quantity Cost during the removal process. Increased © WWF Australia 2003. All Rights Reserved. ($) turbidity (suspended solids) was initially identified as a potential issue Sampling (Travel 10,000 Text: Rebecca Richardson and Phillip Trendell costs not included) Design/layout: Helen Smart during removal, so water quality Sediment control + 1 silt net, 2 5,500 sampling was conducted prior, during oil boom and emer- spill kits 1 oil For copies of this brochure or a full list of and after works. This sampling showed gency spill kits boom WWF Australia publications on a wide range that after the heavy machinery work had Excavator (plus site 1 x 4 days 13,000 of conservation issues, please contact us on: stopped on Day 4, turbidity had delivery) [email protected] or call (02) 9281 5515. returned to a similar level as that prior Trucks 6 x 4 days In Kind to removal. A downstream silt trap Total 28,500 North Region Office played an important role in minimising WWF Australia turbidity increases. Removing debris weirs as a new and exciting option for PO Box 710 from the site also assisted in minimising river rehabilitation. WWF Australia, Spring Hill QLD 4004 environmental impacts in the vicinity. Environmental Trust of NSW, the Great Tel: 07 3839 2677 Fax: 07 3839 2633 Lakes Council and NSW Fisheries have There is potential for erosion of the proven that a partnership approach to Head Office WWF Australia upstream riverbank to occur after barrier removal can be extremely GPO Box 528 removal due to scouring downstream of successful. Sydney NSW 2001 the old crossing. To lessen the potential Tel: 02 9281 5515 Fax: 02 9281 1060 impact, a couple of metres of the References Website: www.wwf.org.au crossing has been retained on both Hobson, M.