Silt up
Definition 1 of 2
Pro Tip 1/3Natural process
Silt up often references natural environmental changes in rivers or lakes. 
Many lakes silt up over centuries.
Pro Tip 2/3Result of activity
It can imply negative consequences of human activities like construction or deforestation. 
Poor farming practices will eventually silt up the downstream riverbed.
Pro Tip 3/3Navigation issues
Silt up can refer to difficulties in navigation for boats due to sediment. 
We couldn't dock because the harbor had silted up over the years.