The Puyallup River and its main tributaries originate in the glaciers of Mount Rainier. These glaciers continually provide sediment such as silt and gravel to the rivers, creating sand and gravel bars. The thick sediment deposits in the stream beds lower water capacity, which causes the river to meander and flood during periods of high streamflow. It also causes the rivers to become braided and meandering. During the summer glacial meltwater dominates the streamflow, turning the Puyallup River turbid. In addition, the glaciers delay the onset of spring-summer runoff, compared to unglaciated river basins.