Complex sentence: Sepulveda Dam and Hansen Dam built in response to 1938's great floods--and after World War II delay, a great public works program to channelize the Los Angeles River and other dry washes maximizes Valley's post-World War II suburban development.
Split into simpler sentences: Sepulveda Dam and Hansen Dam are built in response to 1938's great floods. After World War II delay, a great public works program to channelize the Los Angeles River and other dry washes maximizes the Valley's post-World War II suburban development.