Flooding In Flagstaff

THE 100-YEAR FLOOD

What is a 100-year flood? A 100-year flood is defined as a flood having a 1% chance of occurring in any given year. It does not mean a flood that occurs once every 100 years. 100-year floods can happen at any time and can occur in consecutive years or many times in the same year. The 1993 flooding that created "Lake Continental," was only a 25-year flood, which was of considerably less severity than a 100-year flood.

What conditions could lead to a 100-year flood? For the Flagstaff area the most likely circumstances would be in winter with frozen ground, a good snow-pack, and a period of continuous rain with above-freezing temperatures. It could also occur in periods other than winter if rainfall saturated the soil and the rain continued falling heavily for a long period. Previous wildfires in the watershed can also be a big contributing factor in the severity of flooding.

What areas of Flagstaff can a 100-year flood affect?Many areas in Flagstaff can be affected. Such areas include Cheshire, Coconino Estates, Downtown, Southside, Blackbird Roost, NAU, Continental Country Club, Foxglenn and Sunnyside. Remember, you do not have to live in a floodplain to be flooded.

What are the effects of flooding?Just a few of the impacts of flooding are: threats to the general health and safety of Flagstaff citizens and visitors; damage to buildings, contents, and vehicles; transportation disruptions and delays; power outages; fire; loss of business; damages to roads, bridges, and water/sewer lines; and contaminated flood waters.

WHAT CAN BE DONE TO PREVENT AND MITIGATE FLOODING?

Government agencies. No agency can stop flooding already in progress, but it may be possible to contain and channel it by diking or sand-bagging. The best that government agencies can do is to prepare for flooding through emergency plan-ning and flood control projects to safely channel floodwaters. The City recently received federal funding to design flood control improvements for the Rio de Flag and Clay Avenue Wash on the west side of the City. Engineering design work will begin early next year. The Federal Water Resources Development Act of 2000 is expected to provide the City with funds for the construction of these improvements. The improvements may be completed as early as 2006.