Over the past 160 years, rocks and boulders were removed from the river bottom and used as fill for construction along the river or in the foundations of many buildings within the city. Installing boulders, rock and gravel would contribute to the aquatic diversity of the Grand River. Pocket water, eddies, seams, fast water and slow water all contribute to the oxygenation and overall health of a river. These features also provide healthy structure and habitat for fish and wildlife.