Island Creek is an effluent tributary that breaks out of the Lachlan River some 44 km upstream of Condobolin and rejoins the Little Lachlan River 19 km downstream of its breakout point. Island Creek is but one of a number of distributory creeks that meander across this area of the southern floodplain of the Little Lachlan River. Some 1.2 km upstream of its reentry confluence, a slotted concrete weir structure - Island Creek Weir - has been constructed across Island Creek. The weir is used to divert irrigation flows into Wallamundry Creek, an effluent distributory of Island Creek located some 350 m upstream from the weir.