Cities on Low Ground at Highest Flood Risk

The threat of a wet El Nino winter is attracting widespread interest and apprehension.

But the risk of flooding varies greatly depending on where you live, with older communities in central and western Orange County facing greater hazards than new communities in South County.

County flood-control officials and other water experts say that sections of Huntington Beach, Sunset Beach, Seal Beach and Fountain Valley could sustain the greatest damage during the type of “great flood” that has hit the county three or four times over the last 150 years.

The area is at the end of a watershed that delivers runoff to the ocean from the San Bernardino Mountains and communities to the north. Portions of Huntington Beach and surrounding cities are below sea level, and pumping stations are needed to move runoff away from the low elevations and into the ocean.

The northwestern portion of the county was developed mainly during the 1950s and 1960s, before strict federal flood standards restricted development in flood-prone areas.

“It was a mistake to build anything here,” said Chancy Alexander, whose Huntington Beach neighborhood was flooded during the 1983 El Nino storm. “It was really criminal.”

Alexander and his wife purchased their Driftwood Drive home a year before the storm, unaware that the adjacent flood-control channel could suddenly overflow its banks and send water rushing into their living room.

Before the couple purchased the home, “we went to City Hall, and they told us that there hadn’t been a problem for 30 years,” he said. “Now, we are concerned every time it rains.”

The flood risk is significantly lower among the planned communities that dot South County. Many of the homes in cities such as Mission Viejo, Laguna Niguel and Dana Point were built after federal regulations in the 1970s strictly regulated homes built in flood plains.

Under the federal rules, building in high-risk areas is allowed only if the developer creates a drainage system that protects nearby properties for a once-in-100-years flood.

As a result, many newer planned communities avoided building in low-elevation pockets, which are left for open space.

While Huntington Beach and surrounding communities are flat, the South County has more hills, canyons and valleys that keep runoff contained to certain areas.

“With such topography, you have a more defined watercourse,” said William L. Zaun, the county’s chief engineer.

Anaheim, Yorba Linda, Brea and other North County communities benefit from being at the top of Orange County’s watershed, which transports water generally southward to the ocean. Even with heavy rains, water naturally flows down to coastal cities.

Until the 1940s, this North County area was prone to severe flooding after heavy rains would swell the Santa Ana River. In 1938, a five-day downpour caused the river to jump its banks at Lincoln Avenue in Anaheim, flooding all of western Orange County and killing 58 people.

The destruction led to the construction of the Prado Dam in Corona, which was completed in 1945.

Officials credit the dam with preventing a second disaster in 1969, when heavy rains wreaked havoc throughout the county. Five people in Silverado Canyon died when a mudslide buried them, but the dam helped prevent the Santa Ana River from overflowing and causing a far worse calamity.