Artificial Wetland

BACKGROUND: Greenslopes Reserve is a public green-space park in Mooroolbark, Victoria, frequented by locals for leisurely walks, cycling and dog-walking. The water body at the centre of the Reserve is a constructed wetland, created to collect and treat stormwater from the surrounding residential areas, as well as provide a picturesque amenity for the local community and suitable habitat and refuge for native wildlife. Constructed wetlands provide a natural way to treat and remove pollutants from stormwater before it enters our creeks, rivers and oceans. They help filter water through physical and biological processes, such as sediment ponds, litter traps, ultraviolet treatment (open water) and nitrification/denitrification (wetland plants and algae converting pollutants into Nitrogen gas)1. For these wetlands to function effectively, the vegetation structure, open water surface area and asset functions need to be monitored regularly to ensure continuous performance and to promptly address any issues. RESULTS An initial survey of the site was completed to gain a baseline understanding of the site. Our DJI Matrice 4 Enterprise was used to capture over 800 high resolution photographs of the wetland and surrounding vegetation. For highly accurate results, we used an RTK base station and Ground Control Points. The survey was conducted in the early afternoon, after observing that this was the quietest time of day for foot traffic and dog-walkers. This prevented disruptions to the public and upsetting their pets. Disturbance to wildlife was also minimised by using low-noise propellers, avoiding nesting season and monitoring behaviour. Post data capture, specialised software was used to produce a photogrammetry orthomosaic, providing an impressive high definition and georeferenced map of the site to which further analysis and interpretation could be applied. To complement the orthomosaic image and gain further insight into the terrain and ecological niche of the site, a Digital Terrain Model (DTM) and Digital Surface Model (DSM) were produced. The DTM image depicts a bare earth surface model, showing the level of the water surface in comparison to the surrounding terrain. The DSM captures the heights of all natural and constructed features. The few trees on site can be identified on this model, as well as the vegetation bench within the water zone. This information may be used against artificial wetland design benchmarks to ensure the ideal ratio of vegetation structure is maintained within the wetland. The orthomosaic allowed for a quick and accurate assessment of the asset conditions and litter presence within the wetland. By magnifying the image across the entire site, individual items of litter were captured and mapped, and the inlet and outlet structures of the wetland were assessed – showing overgrowth of vegetation that may be impeding water flow and affecting the function of the wetland. Maintenance actions may be drawn from the interpretation of these results to implement improvements to the wetland and monitor the condition and performance of the site over an extended period. References 1. https://www.melbournewater.com.au/building-and-works/stormwater-management/options-treating-stormwater/constructed-wetlands