FLOOD04688 - Laserfiche WebLink

Home Browse Search

I 3. FLOOD THREAT RECOGNITION I I I I I I I I I I I I I I Flood Threat Recognition consists of actions that enable early identification and subsequent monitoring of potential flood situations. The purpose of the flood threat recognition component is to determine if a flood is impending and predict the time of its occurrence and its magnitude. The flood recognition step is vital to a preparedness program because it provides the trigger for putting the warning arrangements into action. Two approaches are available for flood recognition. The one most commonly used is prediction of floods based on precipitation received in upstream areas. The other is prediction of flooding based on observation of upstream water levels. For the La Junta area, we will use both approaches, or a combination thereof, prediction by the National Weather Service (NWS) of high precipitation and/or the observation of rising water levels around the area, particularly at the Main Street (Colorado State Highway 109) Bridge located in La Junta. The bridge site at Colorado State Highway 109 is used for observation in order to give the maximum protection to the City of La Junta since it's easily accessible and will include all flows from the drainage areas upstream of La Junta. Figure 4 shows the stage information for the State Highway 109 Bridge. In this section, the roles of the various governmental agencies and the identification of the level of threat are discussed. The recognition may begin with the National Weather Service forecast, or with persons/spotters calling to the La Junta Police/Fire Departments or Otero County Sheriff's Department to report observed conditions. 3. 1 Role of the National Weather Service The National Weather Service (NWS) Office in Denver is responsible for flood forecasting. Their Denver Office is a 24 hour a day operation. The National Weather Service Office in Pueblo is open from 6 AM to 10 PM seven days a week. When they are closed, the Denver office takes over their flood forecasting responsibilities. In the event of a flood or flash flood, the NWS will provide the weather and forecast information to the La Junta Police Department and the Otero County Sheriff's Department Dispatchers. The National Weather Service defines floods and flash floods as follows: 1. Floods - slowly evolving overbank flows which are normally caused by water rises due to mountain snowmelt - sometimes augmented by rain at lower elevations. They usually involve gradual river rises and provide a reasonable amount of time for preparing and disseminating watches and warning. These events for La Junta are handled by the National Weather service in Denver, in cooperation with the National Weather Service River Forecast Office in Tulsa, Oklahoma, who has more hydrologic expertise, computer power and modeling capability. In addition, for a flood event, usually, sufficient time is available to produce good forecasts of future river crests and times. I I I I 6 ~ The National Weather Service in Denver provides weather information to the Otero County area.