What is Dam Inundation?

One of the six hazards required in the standardized Natural Hazards Disclosure (NHD) Statement in California is dam inundation. The NHD Statement is required in real estate transactions to protect buyers from inadvertently buying property without realizing the risks they are taking. The NHD Statement is a separate requirement from other standard disclosures, and mandated under the Natural Hazards Disclosure Act (California Civil Code § 1103).

Dam inundation occurs when a dam fails and the water it contains is dumped abruptly into certain areas of a region. This can lead to catastrophic loss of property and lives, more so than regular flooding because the volume and surge of water is much more. Certain locations are particularly vulnerable to flooding when a dam breaks, i.e. low-lying areas are known as inundation areas.

Dams are built precisely to protect regions near large bodies of water from flooding. However, it can fail due to structural weaknesses, improper maintenance, or a combination of the two. A dam may also hold steady but the amount of rainfall may simply be more than the dam is designed to handle. The results will be the same; sudden and major flooding.

Cities in California where dams are near populated areas have maps that follow the lay of the land to identify inundation areas. During particularly heavy rainfall when dam inundation appears imminent, people in the inundation areas may be evacuated just in case. In California, the California Governor’s Office of Emergency Services has the Cal OES Dam Safety Program, which guides and assists local officials on implementing emergency measures in case of a dam failure, coordinates with the California Division of Safety of Dams as well as concerned federal and state agencies, and collects and updates information for dam inundation maps. These maps serve as the basis for NHD Statements.

If you are selling property in California, you will be required to state if the property is in a designated dam inundation area. Contact a disclosure company in your area for quick and easy access to a natural hazard report.

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