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Myths and Facts About Flooding in Pima County

MYTH #1: The October, 1983 flood was the 100-year flood for every wash in Tucson and Pima County.

FACT: The Santa Cruz River, Rillito Creek and Brawley Wash reached near 100-year flood levels. Most small washes experienced relatively minor flooding during 1983.

MYTH #2: Since we recently had a 100-year flood, we will be safe from flooding for another 100 years.

FACT: Floods have no memory of the past and 100-year floods can occur in consecutive years. For example, the Salt River in the Phoenix metropolitan area experienced 100-year floods in three consecutive years in 1978, 1979 and 1980. Floods that are smaller or larger than the 100-year flood can also cause major damages.


MYTH #3: If your house or property was not flooded in the 1983 or the 1993 flood, then it is not in the floodplain and you don't need to be concerned about flooding.

FACT: Most washes in Pima County, particularly the smaller washes, did not experience major flooding during the 1983 or 1993 events. Large scale flooding events don't necessarily serve as good indicators of whether a house or property may be in the floodplain or whether it is subject to flooding.


MYTH #4: If I locate my home outside the floodplain I will never have any flood damages.

FACT: Not necessarily true! Erosion along desert washes can be extensive. A watercourse can migrate and move closer to a building. Also, floods larger than the regulatory 100-year flood can occur.


MYTH #5: If it is not raining in my neighborhood, then the wash I'm next to will not flow.

FACT: Flash floods can move miles downstream and inundate areas that didn't receive rain. On July 26, 1981, seven people died when a flash flood hit unexpectedly at Tanque Verde Falls.


MYTH #6: Placing branches along the embankment of a wash is an effective method of flood protection.

FACT: Larger flows will move buoyant materials downstream where they collect and almost always worsen flood damages.


MYTH #7: If a roadway dip section looks like it only has six or eight inches of water running over it, then it is safe to drive across.

FACT: This is false... but it's one of the hardest lessons to learn. You can see that there's water in the roadway dip section... BUT...the pavement underneath the water may have eroded or completely washed away. If the pavement is no longer there, the wash crossing could be several feet deep­ or more­ and be extremely hazardous.


MYTH #8: I can make any drainage improvement I need to on my own private land as long as the flow enters and leaves my property at the same location.

FACT: All drainage improvements involving a regulatory floodplain require a permit. Numerous drainage problems and drainage violations are caused as a result of inadequate or inappropriate drainage improvements.