Sea walls are large scale constructions built along a coastline to protect from rising waters and destructive waves. Often the height of seawalls is legislated by a municipality. They are typically quite costly, and as a result are only used in more dire situations, with more cost-effective options such as beach nourishment more commonly used. Sea walls inhibit the natural patterns of tides and sediment exchange, weakening the stability of the beach and diminishing the limits of the beach itself. Sea walls only protect their area, potentially diverting erosion to other, less protected areas. Sea walls are generally unsightly and must be consistently maintained, limiting their usefulness. Sea walls are generally a controversial topic, and should not be considered as a first line of defense unless where necessary.