A Levee is an embankment built along the sides of rivers, streams and the sea as vertical or sloping walls. They are usually made of mud and prevent flooding by stopping the water from flowing into areas that lie beside the water body by blocking it.
To construct a levee a small area along the side of the water body is cleared. Earth is deposited on this plain area as structures which taper upwards. A small flat area is also created on top so that additional material could be piled there in case the water level equals that of the levee. After the earth has been deposited measures have to be implemented to prevent erosion, both on the side facing the river as well as the opposite side.
Even if a small portion of a levee fails it is equivalent to the whole structure failing and large areas beside the water bodies can get flooded. This requires that the regulations which are meant for construction of a levee are strictly adhered to.