Hydrologic technician uses a gravelometer

A gravelometer is a field tool used to measure and classify the size of sediment particles, like gravel, cobbles, and boulders, in streams and rivers. It’s a rectangular metal plate with different sized holes corresponding to standard grain-size classes. For freshwater mussels like the western pearlshell, streambed sediment size is a critical component of habitat quality. Characterizing the sizes of streambed sediment particles is helpful for assessing whether streambeds offer the right conditions for mussels to thrive.