mud or clay or small rocks deposited by a river or lake
"The heavy rains caused the swollen creek to deposit thick layers of silt across the meadow, turning the green grass into brown sludge."
Mud or fine earth deposited from running or standing water.
"The riverbank had eroded over time, leaving a thick layer of silt where the current slowed near the bend."
To clog or fill with silt.
"The heavy rains caused the river to swell and quickly silt up the narrow drainage channels, stopping all water flow until the blockage was cleared."