 With 5,005,400 inhabitants (as of 2016) and an urban population density of 2037 people per square kilometre, Sydney's urban area covers , comprising 35% of Sydney and is constantly growing.The rising sea level between 18,000 and 6,000 years ago flooded the rias to form estuaries and deep harbours.Erosion by coastal streams has created a landscape of deep canyons and remnant plateaus.