|CSS were engaged by the Sydney Metropolitan CMA to complete subcatchment delineation for the Lower Parramatta River, Lane Cove River and Middle Harbour catchments, which occupy approximately 350 km2 of the Sydney urban area. The project was completed as part of the Sydney Harbour Water Quality Improvement Plan.|
The subcatchments and associated hydrologic parameters were to be used for both water quality and flood modelling purposes. Accordingly, detailed subcatchment delineation was necessary to ensure the objectives of both modelling applications could be met. Therefore, CatchmentSIM was used to subdivide each catchment based on a 2 m DEM derived from ALS and bathymetric survey information. Approximately 1,250 subcatchment were subsequently delineated using CatchmentSIM and a range of hydrologic parameters were calculated for each subcatchment including area, average vectored slope, % impervious and main stream length. The subcatchments and associated parameters were provided to the CMA for inclusion in their GIS and to assist in the development of detailed XP-RAFTS hydrologic models of each catchment. CSS also extracted representative river and creek cross-section information (including Manning’s ‘n’ roughness estimates) for each subcatchment/river reach for use in parameterising the XP-RAFTS model links.
The hydrographs generated by the XP-RAFTS model will be used to define continuous historic hydrographs in catchment pollutant export models that are also being developed by CSS as part of the Sydney Harbour Water Quality Improvement Plan project.