Dewatering of scour pools at the toe of existing spillways can significantly increase forces on such structures and reduce their overall stability below acceptable levels. Such dewatering may be required however to undertake needed repairs or to construct a stilling basin. Use of a braced cofferdam permits the necessary dewatering while at the same time temporarily improving the stability of the spillway. This is accomplished by mobilizing earth pressures and tailwater pressures through the braces to restrain the spillway against sliding
