13.2 The Wallis Lake Estuary Management Committee - Great Lakes ...

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Wallis Lake Estuary Management Plan Recommendations from the conservation strategy were employed in the CDS, however this will soon be replaced by the biodiversity strategy that is currently being prepared. When this occurs it is recommended that the conservation zones of the CDS be reviewed. 13.1.10 Forster/Tuncurry Floodplain Management Plan The Forster/Tuncurry Floodplain Management Plan, finalised in 1998, provides the ‘basis for future management of flood liable lands and the management of development within the Forster and Tuncurry floodplain areas’. Structural (ie. levees and dredging) as well as non-structural (effective flood warning and evacuation systems) options were investigated and evaluated for their effectiveness in reducing flood damages. Non-structural options were deemed to be most cost-effective, and the following key measures were recommended: • flood forecasting system • preparation of a detailed evacuation plan • flood awareness and public education • voluntary house raising, and • planning and development controls. 13.1.11 Wallamba River Floodplain risk management plan for Nabiac, Failford and Minimbah areas The Wallamba River floodplain risk management plan concentrates on extent of flooding from the Wallamba River only and the risk to surrounding buildings where data is available. The document proposes methods of dealing with existing, future and continuing flood risk. In summary, six prioritised actions were proposed: • updating development controls to manage future flood risk • flood planning, education, awareness and data collection to manage continuing flood risk • timely review this floodplain risk management plan following completion of investigations into the tributaries or at a maximum of 5 year intervals • upgrading of access issues in key areas as identified in emergency management planning including Willow Point Road at Failford and Glen Ora Road at Minimbah • voluntary house raising to manage existing flood risk, and • voluntary purchase to manage existing flood risk where dwellings cannot be raised. 13.1.12 Wallis Lake wetland management strategy GLC aims to begin preparing a wetland management strategy in 2005 to addresses the recommendations made in the wetlands action plan of the WLCMP. The anticipated goals of this plan will be to identify the wetland areas in Wallis Lake, apply for RAMSAR listing of the wetlands under the international convention, and then implement best practice management guidelines and management criteria under the RAMSAR convention to conserve and enhance existing wetlands. 13.1.13 Identification of urban and rural inputs to sediments in Wallis Lake – Chief Investigators: Logan G. A., MacPhail M., Fredericks D., Smith C. and Heggie D. (2001) 124
Wallis Lake Estuary Management Plan This study was conducted in response to the identification of nutrient and animal faecal pollution in areas of Wallis Lake during the estuarine processes study (Webb, McKeown and Associates). In order for adequate management controls to be implemented addressing this issue more information was required on the sources and sinks of this pollution. This is typically a difficult task due to the physical processes of tides and run-off as well as other climatic and biological factors contributing to the complex movement of pollutants once they have entered the estuarine environment. Lipid biomarkers and pollen analysis were used in this study as tracers of nutrient and faecal pollution. Lipid biomarkers are of biological origin and can be very specific to groups of organisms such as types of phytoplankton or terrestrial plants. In addition to this certain biomarkers can be used to assess the source and degree of faecal contamination. Different types of pollen can be visually distinctive, and can therefore be traced back to the parent plant or plant communities. This allows an indication of various sediment sources and sedimentation rates within Wallis Lake. The composition of lipid biomarkers and pollen in sediment samples at potential end members of rural and urban inputs was assessed. The lipid biomarkers and pollen composition was found to be indicative of certain catchments, thus allowing the input of organic matter into the Lake from these areas to be mapped. No evidence of faecal input was found at any of the sites surveyed. However, herbivore faecal contamination was detected in sediments at the end member sites of the Wallamba and Coolongolook/Wang Wauk Rivers. This study identified a number of indicators that can be used to monitor faecal contamination in sediments and sedimentation rates. These indicators will prove to be very useful when assessing any potential benefits from implementation of estuary and catchment management programs for erosion or nutrient/faecal pollution control. 13.1.14 Benthic nutrient fluxes in Wallis Lake – Chief Investigators: Smith C. S., Heggie D. T., Fredericks D. J., Palmer D. W. and Logan G. A. (2000 and 2003) Benthic nutrient fluxes are a measure of the transport of nutrients between the bottom sediments and the overlying water column. By quantifying these transports we can calculate the denitrification efficiency of benthic sediments. Denitrification is an important natural way for estuaries to cleanse themselves of excess nitrogen. It is a process by which nitrogen from plant organic material is converted to nitrogen gas by denitrifying bacteria and lost to the atmosphere. If this process is not operating efficiently, the organic nitrogen is instead converted to dissolved inorganic forms (nitrate, nitrite and ammonia) and is available for plant growth. If the dissolved inorganic nitrogen concentration exceeds the assimilative capacity of the system, eutrophication can occur. Eutrophication is a process of excess plant growth resulting in algal blooms, particularly of phytoplankton and free floating macroalgae. This is particularly detrimental to seagrasses, which can then be out-competed due to shading. Therefore by measuring the benthic nutrient fluxes of Wallis Lake sediments assessments can be made on the trophic state of the water body and risk of eutrophication at specific study sites. 125
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