Because they do
Levees are built along the banks of rivers
Natural levees are built up over time from debris and sediment whereas artificial levees are man made using sand bags and larger rocks.
A levee is a natutral or artificial embankment built along a rivercourse, or an arm of the sea, to protect adjoining land
levees
Levees, dikes.
The embankments are called levees. When the levees around New Orleans failed during and after Hurricane Katrina it led to catastrophic flooding. Note that money had been allocated for work on the levees prior to that but it was decided to use it to improve the roads on top of the levees which, technically, was an "improvement" but one wonders how it would have all played out if it had instead been used to improve the strength of those those levees prior to Katrina.
..... stop floods, just like the levees on the Mississippi.
levees or banks
along rivers
dams
Some people in the southern United States adapted to Mississippi River floods by building their houses on stilts. The Army Corps of Engineers built many levees along the river to keep flood waters back.
there can be all sorts along major rivers like dams statues.