The study area was taken as the channel and floodplain downstream of Oakhampton Railway Bridge on the Hunter River, and Dunmore Bridge on the Paterson River, to Green Rocks on the Hunter River. The hydraulic model was extended beyond the study area to ensure that the study area was accurately modelled and not subject to "boundary" effects. Results from the model outside the defined study area should not be used in floodplain management without additional checking. The major catchments feeding into the hydraulic model are:

• Hunter River catchment to Maitland
• Paterson River catchment to Gostwyck
• Williams River catchment to Glen Martin
• Fishery Creek (Wentworth Swamp)
• Wallis Creek (Dagworth Swamp)