Water helped sustain Seneca’s businesses and households, as the Seneca Sandstone Quarry shipped cut red sandstone on the Potomac River through the C & O Canal and the Seneca Grist Mill used Seneca Creek to power its waterwheel, but the community’s position at the mouth of a watershed covering a third of Montgomery County also left it exposed to destructive flooding. By the 1950s, developers predicted that increasing development in the Seneca Basin would bring frequent and powerful floods, and Hurricane Agnes in 1972 devastated Seneca, damaging or destroying half of the 40 buildings along the creek. Because a 1965 Montgomery County building code required a minimum setback of 500 feet from the banks of Seneca Creek, those structures could not be rebuilt. Flood management experts instead recommended acquiring the area for nature conservation, and in the 1970s M-NCPPC purchased land in Seneca through its stream valley park acquisition program to aid watershed management while creating a retreat from urban pressures with scenic waterscapes, picturesque terrain, and varied plant and animal life.