Question - Why do the wing dykes on the Mississippi River increase the risk of flooding in upstream areas, and why to the levees (dykes along the sides of the river)

Why do the wing dykes on the Mississippi River increase the risk of flooding in upstream areas, and why to the levees (dykes along the sides of the river) increase the risk of flooding in downstream areas?

Answer:

Wing dykes on a stream act like partial dams. They reduce the rate of water flow and that can exacerbate flooding in upstream areas. Dykes along the side of a river prevent flooding in that area so that water that might otherwise have been temporarily stored on the flood plain quickly passes through, increasing the potential for flooding in downstream areas.