The geomorphic character and hydrological function of an upland swamp, Budderoo Plateau, Southern Highlands, NSW, Australia

Upland swamps are a form of topogenous mire which occur on the plateau areas of southeastern Australia. These systems are well recognised for their ecological value and their functional role in the hydrodynamics of the catchments in which they occur. However, little is known about how the internal hydrological functioning of upland swamps relates to their geomorphic structure. The sedimentological, geomorphic and hydrological properties of an intact upland swamp on the Budderoo Plateau NSW are investigated. The geomorphic structure of the swamp is comprised of four distinct geomorphic zones: the central swamp, the headwater marginal swamp, the valley marginal swamp, and the hillslope zones. The sedimentological structure of the swamp is relatively consistent, and comprises of a basal layer of coarse sands, overlain by organic accumulations up to 3.3 m in thickness. Each of these sedimentary units has different hydrological behaviours (rates of water transfer and discharge) that drive the overall function of the swamp in response to rainfall of various magnitudes and duration. Three hydrological response regimes have been identified in the functioning of this swamp. These regimes are characterised by different peak and recession responses to rainfall. The form of the hydrograph produced is controlled by antecedent water table position and the amount, timing and duration of rainfall. Depending on antecedent moisture conditions, the swamp can be operating either as a store for water or as a rapid conduit for water throughflow and overland flow. It therefore has a dual function in terms of flow generation in response to rainfall.