This advisory is issued for the non- telemetered river basins. It is done as situation warrants (e.g. during inclement weather affecting the river basins in the particular region) . Normally it is issued at 7:00 AM and 7:00 PM.
a. Present weather situation – describes the current weather system affecting the country based on the weather advisory issued by the weather forecasting section
b. Forecast 12-hour rainfall - gives the forecast rainfall for the next 12 hours based on all available models (e.g. Light, moderate, heavy)
c. List of watercourses that are likely to be affected – gives the list of all the tributaries that will be affected given the forecast rainfall in the particular region.
d. Public warning – describes the suggested actions as to what the people and (local) disaster risk reduction and management council would do.
Preparation of Flood Forecast
The preparation, issuance and dissemination of an adequate and timely warning is the ultimate purpose of flood forecasting. Timeliness is an essential requirement for a flood warning. A sufficient lead time enables the ultimate user to take the necessary precautionary countermeasures.
The hydrological and meteorological conditions in a river basin and the consequent state of its river system is never constant. The behavior of the river itself is the resultant of the interaction of all hydrological processes and conditions in the river basin.
A flooding situation is not a daily occurrence. However, flood forecasting operations must, of necessity, be a continuous activity. It is carried out from day to day even when the possibility of a flood is highly improbable. This mode of operation enables flood forecasters to pinpoint the beginning of a potential flood-generating situation.
Like storm bulletins which are issued only during the presence of tropical cyclones, flood forecast and warning bulletins are prepared only when a potential flooding situation is definitely present. They are issued regularly at specified hours of the day for the duration of the flooding period until the flood recedes or when all hazards and dangers associated with the phenomenon are no longer present.
The prevailing hydrometeorological situation in a given river basin defines the operational environment under which flood forecasting and warning operations are carried out. Conveniently categorized into
- normal situation,
- alert phase, and
- warning phase
In practice1 flood bulletins are issued as soon as the development of a flooding situation exists. The initial bulletin serves merely to alert the people in the threatened basin to the possibility of a flood. It is never intended to categorically state that there will be flooding but only of the possibility. The initial bulletin is issued as soon as the operational situation passes from the alert to the warning phase. The transition from one operatiohal status to another is based on pre-determined criteria.
Thus, flood forecasting operation needs to be a continuing activity to determine the point in time when the operational situation passes from one phase to another. A flood forecasting operation consists of the following:
This requires the collection, at regular interval, of the real-time data on rainfall, water level and other information that affect the hydrological condition of the river basin and the state of the river system. This provides a broad picture of the current situation in a river basin.
The data are analysed and related to other available information such as storm data from radar and satellite observation. The general objective here is to deduce the probable development in the hydrological situation in the river basin in the near future. This part of the operation involves a variety of hydrological analyses as well as the use of flood forecasting models to provide an objective estimate of the forecast situation.
Preparation of the forecast and warning:
Flood forecasts are completed in time for release at regular preset time of issuance. Dissemination is made through disseminating agencies such as the OCD1 DSWD, NDCC, and thru the mass media, particularly radio and television.
There are three categories of flood information intended for the general public. All are issued under the general title of "Flood Bulletin". A distinct series of bulletins is issued for each threatened river basin where the forecasting and warning service is already extended and operational. As already stated, bulletins are issued only when conditions,
i.e., there is a potential flooding situation, so warrant their issuance.
When required, flood bulletins are prepared twice daily. They are completed and readied for issuance and dissemination at 5 a.rn. and 5 p.rn., respectively, when it is deemed early enough to provide vital information for concerned users to take necessary countermeasures before they leave for work in the morning or before they retire at night.
A series of bulletins for a given affected river basin is ideally initiated by a Flood Outlook. As the category implies, the bulletin merely states the present hydrological situation and alerts the people in a basin to the possibility of a deteriorating condition, e.g., a gradual and continuous rise in the water level.
Subsequent bulletins could be of any one of the three categories. Normally, for a given affected basin, one bulletin is followed by another of the same in the next higher category depending on the development in the hydrological condition and the forecast situation. Hence, an Outlook is followed by another Outlook or by a Flood Advisory; or by a Flood Warning.
When the situation had clearly reached its worst such that, at most the condition or, at best, improvement can be expected, subsequent bulletins are of the same or by a next lower category than the proceeding.
Upon receipt of the coded messages, they are decoded and each set of observations is plotted in symbols or numbers on weather charts over the respective areas or regions. Observations made over land and sea are plotted on the surface or mean sea level charts which are prepared four times a day. Radiosonde, theodolite, aircraft and satellite wind observations are plotted on upper level charts which are prepared twice daily.
Flood bulletins are specifically directed to the public. They are intended to apprise the people in the threatened area of the present situation and of the expected development. It suggests the appropriate actions the community may have to take to prevent or mitigate the disastrous effects of a flood.
As in any kind of disaster, the best countermeasures for flood damage prevention and mitigation are those which are community efforts.
Floods cannot be prevented. To a large extent, however, they can be controlled effectively. By this is meant keeping the river from overflowing. There are a number of ways of accomplishing this before and during a flood:
- increasing the flow capacity of a river by cleaning the channel of debris, by dredging, by straightening of channels, etc.;
- construction of dikes and levees; and
- sandbagging during floods.
Individually and collectively, people in a flood-stricken area must take precautionary measures to ensure personnel safety and health:
- People, particularly children, should avoid wading in floodwaters.
- Where houses are expected to be flooded, people should move to higher places.
- Electrically operated appliances should be transferred to upper storeys of buildings.
- When electrical fines and outlets will be submerged in floodwater, power should be switched off.
Flood Safety Rules
BEFORE THE FLOOD:
- Find out how often your location is likely to be flooded.
- Know the flood warning system in your community and be sure your family knows it.
- Keep informed of daily weather condition.
- Designate an evacuation area for the family and livestock.
- Assign family members instructions and responsibilities according to an evacuation plan.
- Keep a stock of food which requires little cooking and refrigeration; electric power may be interrupted.
- Keep a transistorized radio and flashlight with spare batteries, emergency cooking equipment, candies, matches and first aid kit handy in case of emergency.
- Store supplies and other household effects above expected flood water level.
- Securely anchor weak dwellings and items.
- Watch for rapidly rising flood waters.
- Listen to your radio for emergency instructions.
- If you find it necessary to evacuate, move to a safe area before access is cut off by flood waters.
- Store drinking water in containers, water service may be interrupted.
- Move household belongings to upper levels.
- Get livestock to higher ground.
- Turn off electricity at the main switch in the building before evacuating and also lock your house.
- Avoid areas subject to sudden flooding.
- Do not attempt to cross rivers of flowing streams where water is above the knee.
- Beware of water-covered roads and bridges.
- Avoid unnecessary exposure to the elements.
- Do not go swimming or boating in swollen rivers.
- Eat only well-cooked food. Protect leftovers against contamination.
- Drink clean or preferably boiled water ONLY.
- Re-enter the dwellings with caution using flashlights, not lanterns or torchers. Flammables may be inside.
- Be alert for fire hazards like broken wires.
- Do not eat food and drink water until they have been checked for flood water contamination.
- Report broken utility lines (electricity, water, gas and telephone) to appropriate agencies authorities.
- Do not turn on the main switch or use appliances and other equipment until they have been checked by a competent electrician.
- Consult health authorities for immunization requirements.
- Do not go in disaster areas. Your presence might hamper rescue and other emergency operations
THINGS ONE CAN DO TO MITIGATE FLOODS:
- Regulate cutting of trees.
- Report illegal loggers and kaingeros.
- Report illegal construction of fishponds and other establishments in waterways.
- Do not throw garbage in esteros and rivers.
- Help clean the neighborhood.
- Support community activities intended to lessen the occurrence of floods.
- Avoid throwing anything like plastic wrappers anywhere which may clog or block the drainage system.