sentences:  The flood risk to the state capital had been exacerbated since the 1850s by hydraulic mining debris and the construction of levees to protect farms and towns, which reduced the channel capacity of the Sacramento and American Rivers.The current dam was originally authorized by Congress in 1944 as a flood control unit, and was reauthorized in 1949 as a multiple-purpose facility.The current Folsom Dam replaced an earlier, smaller dam that had been completed in 1893 by Horatio Gates Livermore.