Nothing in this chapter contained shall be construed as affecting or in any wise limiting the powers of counties, cities, towns, diking districts, drainage districts, or other municipal or public agencies in the manner authorized by law to construct and maintain dikes, levees, embankments or other structures and works, or to open, deepen, straighten and otherwise enlarge natural water courses, waterways and other channels, for the purpose of protecting such organizations from overflow.
RCW 86.09.900