Bennett Brook's catchment area covers . Approximately half of the catchment area is covered by
Whiteman Park and the Gnangara Pine Plantation. The rest of the catchment is urbanised, covering the suburbs of
Ballajura,
Beechboro,
Bennett Springs,
Kiara,
Lockridge,
Malaga,
Morley and
Noranda. The tributaries to the west are highly modified and partially underground. The tributaries to the north are mostly natural. Upstream areas only flow between August and November. Groundwater pumping from the
Gnangara Mound has made the flow lower than the natural flow. Downstream areas flow year round. Urbanisation has made the flow downstream higher than the natural flow, due to higher
surface runoff from roads and houses. ==Bridges==