The levees protecting those communities are weakening over time.
Hurricane Katrina forced the government to take a second look at their flood maps. People now living within the flood hazard zones may be forced to purchase more insurance.
Riverdale is a small community of more than 2,000 people. The entire area is now relabeled as a flood hazard zone even though the Kings River is about 6 miles away.
Don Askew built his house in 1972 knowing flood waters have not reached here in recent memory.
"Like I say the old timers tell me it hadn't flooded in the last hundred years that they know of," says Askew.
In 2006 water from Millerton Lake spilled over Friant Dam after a record snow pack melted. The valley witnessed weak levees breaking and causing widespread flooding.
A fear very close to Kris Brassart's heart. She lives across the street from a levee protecting her from the Kings River.
Laton resident Brassart wished the government would take a proactive approach rather than rezoning her community.
"They probably need to make sure and take care of the banks ... Maintain them. There aren't that many houses out here but enough to cause a problem for the housing and families that live around here," says Brassart.
Fresno County Supervisor Henry Perea expects lenders to force their homeowners to buy flood insurance. But the county may take the expensive action of strengthening levees.
Perea says, "Long term, I believe we're going to have to start looking at the conditions of the levees that we have in those areas as well as the wisdom of allowing future construction in those areas and that is something the county controls from the land use perspective."
Most people who live in the newly rezoned areas don't know about the change. Perea says the county will soon begin notifying residents.