A flood warning is closely linked to the task of
flood forecasting Flood forecasting is the use of forecasted precipitation and streamflow data in rainfall-runoff and streamflow routing models to forecast flow rates and water levels for periods ranging from a few hours to days ahead, depending on the size of the ...
. The distinction between the two is that the outcome of flood forecasting is a set of forecast time-profiles of channel flows or river levels at various locations, while "flood warning" is the task of making use of these forecasts to make decisions about whether warnings of floods should be issued to the general public or whether previous warnings should be rescinded or retracted.
The task of providing warning for floods is divided into two parts:
* decisions to escalate or change the state of alertness internal to the flood warning service provider, where this may sometimes include partner organisations involved in emergency response;
* decisions to issue flood warnings to the general public.
The decisions made by someone responsible for initiating flood warnings must be influenced by a number of factors, which include:
* The reliability of the available forecasts and how this changes with lead-time.
* The amount of time that the public would need to respond effectively to a warning.
* The delay between a warning being initiated and it being received by the public.
* The need to avoid issuing warnings unnecessarily, because of the wasted efforts of those who respond and because a record of false alarms means that fewer would respond to future warnings.
* The need to avoid situations where a warning condition is rescinded only for the warning to be re-issued within a short time, again because of the wasted efforts of the general public and because such occurrences would bring the flood warning service into disrepute.
A
computer system for flood warning will usually contain sub-systems for:
*
flood forecasting Flood forecasting is the use of forecasted precipitation and streamflow data in rainfall-runoff and streamflow routing models to forecast flow rates and water levels for periods ranging from a few hours to days ahead, depending on the size of the ...
;
* automatic alerting of internal staff;
* tracking of alert messages and acknowledgements received;
* diversion of messages to alternates where no acknowledgement received.
National Flood Warning Services
The type of flood warning service available varies greatly from country to country, and a location may receive warnings from more than one service.
Philippines
In the
Philippines
The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no),
* bik, Republika kan Filipinas
* ceb, Republika sa Pilipinas
* cbk, República de Filipinas
* hil, Republ ...
, the
(PAGASA) branch of the
Department of Science and Technology (DOST) issues general flood advisory (for non-telemetered river basins whenever there is a significant amount of rainfall recorded).
United Kingdom
Arrangements for flood warnings vary across the United Kingdom with several agencies leading on warnings for emergency responders and the public. The
Environment Agency
The Environment Agency (EA) is a non-departmental public body, established in 1996 and sponsored by the United Kingdom government's Department for Environment, Food and Rural Affairs, with responsibilities relating to the protection and enha ...
,
Natural Resources Wales and
Scottish Environment Protection Agency all undertake location specific flood warning activities for communities at risk depending upon the scale of flood risk, technical challenges and investment needed to deliver a reliable service.
Prior to issuing a flood warning consideration is given to:
* the needs of communities to activate emergency response plans
* the nature of the catchment or coastline and the lead time that may be provided
* meteorological observations and forecast information on rainfall and coastal water levels
* hydrological observations and flood forecasts
* reference to thresholds of historic or forecast flood levels
Dissemination of flood warnings has moved towards a service whereby those at risk can pre-register to receive warnings by phone, email or text message from an automatic system, Floodline. Both warnings and updates about current conditions are also carried by local
radio station
Radio broadcasting is transmission of audio (sound), sometimes with related metadata, by radio waves to radio receivers belonging to a public audience. In terrestrial radio broadcasting the radio waves are broadcast by a land-based radio ...
s. In addition, live updates are carried by the Environment Agency's website, showing which locations have flood warnings in place and the severity of these warnings.
There is currently no flood warning system in Northern Ireland, but the
Met Office
The Meteorological Office, abbreviated as the Met Office, is the United Kingdom's national weather service. It is an executive agency and trading fund of the Department for Business, Energy and Industrial Strategy and is led by CEO Penelope E ...
does issue weather warnings.
Flood risk management is the responsibility of
Rivers Agency
DfI Rivers is an Executive Agency of the Department for Infrastructure (DfI), in the Northern Ireland Executive. It is the statutory drainage and flood defence authority for Northern Ireland under the terms of the Drainage (Northern Ireland) Order ...
in Northern Ireland. Consideration will be given to the introduction of a warning system as part of the implementation of the EU
Floods directive
The Floods Directive (Directive 2007/60/EC) is legislation in the European Parliament on the assessment and management of flood risks. The floods directive basically prescribes a three-step procedure:
First step: Preliminary Flood Risk Assessme ...
.
United States
In the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
, the
National Weather Service
The National Weather Service (NWS) is an Government agency, agency of the Federal government of the United States, United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weathe ...
issues flood watches and warnings for large-scale, gradual river flooding. Watches are issued when flooding is possible or expected within 12–48 hours, and warnings are issued when flooding over a large area or river flooding is imminent or occurring. Both can be issued on a county-by-county basis or for specific rivers or points along a river. When rapid flooding from heavy rain or a dam failure is expected,
flash flood watch
A flash flood watch ( SAME code: FFA; also referred as a "green box" by meteorologists) is severe weather watch product of the National Weather Service that is issued when conditions are favorable for flash flooding in flood-prone areas, usually ...
es and
warnings are issued.
In the U.S. and
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
, dissemination of flood warnings is covered by
Specific Area Message Encoding
Specific Area Message Encoding (SAME) is a protocol used for framing and classification of broadcast emergency warning messages. It was developed by the United States National Weather Service for use on its NOAA Weather Radio (NWR) network, and w ...
(SAME) code FLW, which is used by the U.S.
Emergency Alert System
The Emergency Alert System (EAS) is a national warning system in the United States designed to allow authorized officials to broadcast emergency alerts and warning messages to the public via cable, satellite, or broadcast television, and both ...
and
NOAA Weather Radio
NOAA Weather Radio NWR; also known as NOAA Weather Radio All Hazards is an automated 24-hour network of VHF FM weather radio stations in the United States (U.S.) that broadcast weather information directly from a nearby National Weather Serv ...
network and in Canada's
Weatheradio Canada
Weatheradio Canada (french: Radiométéo Canada) is a Canadian weather radio network owned and operated by Environment and Climate Change Canada's Meteorological Service of Canada division that is an official partner of the U.S. National Weather ...
network.
"Flood statements" are issued by the
National Weather Service
The National Weather Service (NWS) is an Government agency, agency of the Federal government of the United States, United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weathe ...
to inform the public of flooding along major streams in which there is not a serious threat to life or property. They may also follow a flood warning to give later information.
Example of a flood warning
The following is an example of a "Flood Warning." The
Sabine River is used as an example:
394
WGUS44 KSHV 070219 RRA
FLWSHV
BULLETIN - IMMEDIATE BROADCAST REQUESTED
Flood Warning
National Weather Service Shreveport LA
819 PM CST Wed Jan 6 2021
...The National Weather Service in Shreveport LA has issued a Flood
Warning for the following rivers in Texas...
Sabine River Near Hawkins affecting Wood, Smith and Upshur
Counties.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Do not drive cars through flooded areas.
Caution is urged when walking near riverbanks.
A Flood Warning means that flooding is imminent or occurring. All
interested parties should take necessary precautions immediately.
Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.
For more hydrologic information, copy and paste the following website
address into your favorite web browser URL bar:
water.weather.gov/ahps2/index.php?wfo=shv
TXC423-459-499-080230-
/O.NEW.KSHV.FL.W.0009.210109T0430Z-210111T0224Z/
/HAKT2.1.ER.210109T0430Z.210110T0000Z.210110T2024Z.NO/
819 PM CST Wed Jan 6 2021
The National Weather Service in Shreveport has issued a
* Flood Warning for
the Sabine River Near Hawkins.
* From Friday evening to Sunday evening.
* At 7:45 PM CST Wednesday the stage was 19.1 feet.
* Flood stage is 23.0 feet.
* Minor flooding is forecast.
* Forecast...The river is expected to rise above flood stage late
Friday evening to a crest of 23.7 feet Saturday evening. It will
then fall below flood stage early Sunday afternoon.
* Impact...At 23.0 feet, minor lowland flooding. Move livestock and
equipment to higher ground.
&&
LAT...LON 3263 9535 3257 9509 3253 9508 3254 9521
3257 9535
$$
19
Source:
Example of a flood statement
000
WGUS84 KMRX 221008
FLSMRX
FLOOD STATEMENT
NATIONAL WEATHER SERVICE MORRISTOWN, TN
608 AM EDT TUE SEP 22 2009
...THE FLOOD WARNING CONTINUES FOR THE FOLLOWING RIVERS IN GEORGIA...
TENNESSEE...
SOUTH CHICKAMAUGA CREEK @ CHICKAMAUGA TN AFFECTING CATOOSA AND
HAMILTON COUNTIES
IN HAMILTON COUNTY...THERE ARE TOO MANY STREETS CLOSED TO MENTION.
IN SHORT...BE PREPARED FOR LONG DELAYS. ALSO...FAR TOO MANY PEOPLE
ARE TRYING TO DRIVE THROUGH FLOOD WATERS. THIS IS A GOOD WAY TO DIE.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
MOST DEATHS IN FLOODS OCCUR IN CARS! IF YOU COME TO A CLOSED OR
FLOODED ROAD, TURN AROUND! DON'T DROWN! DRIVING INTO FLOODED ROADS
IS A GOOD WAY TO DIE. BETTER TO BE LATE THAN END UP ON THE NEWS.
&&
GAC047-TNC065-221608-
/O.CON.KMRX.FL.W.0013.000000T0000Z-090923T1942Z/
/CHKT1.2.ER.090921T0923Z.090922T1800Z.090923T1342Z.NO/
608 AM EDT TUE SEP 22 2009
THE FLOOD WARNING CONTINUES FOR
THE SOUTH CHICKAMAUGA CREEK @ CHICKAMAUGA TN
* UNTIL WEDNESDAY AFTERNOON.
* AT 5:15 AM TUESDAY THE STAGE WAS 25.8 FEET.
* MODERATE FLOODING IS OCCURRING. THE FORECAST IS FOR MODERATE
FLOODING TO CONTINUE.
* FORECAST...THE RIVER WILL CONTINUE TO RISE AND CREST NEAR 26.5 FEET
TUESDAY AFTERNOON. THE RIVER WILL FALL BELOW FLOOD STAGE LATE
WEDNESDAY MORNING.
* AT 27.0 FEET...HOMES ON ARLENA CIRCLE (OFF SHALLOWFORD ROAD) ARE
EVACUATED. EVACUATIONS ALSO TAKE PLACE AT THE FOUNTAINBLEAU
APARTMENTS ON SPRING CREEK ROAD IN EAST RIDGE.
$$
$$
BOYD
Source:
Iowa Flood Center
The Iowa Flood Center at the
University of Iowa
The University of Iowa (UI, U of I, UIowa, or simply Iowa) is a public university, public research university in Iowa City, Iowa, United States. Founded in 1847, it is the oldest and largest university in the state. The University of Iowa is org ...
operates the largest real-time flood monitoring system of its kind in the world. It includes more than 200 real-time stream stage sensors that feed data into the Iowa Flood Information System where data can be viewed, online, by disaster management staff and the general public. The stream stage sensors, mounted on bridges and culverts, use ultrasonic sensors to monitor stream and river levels.
References
External links
Flood Risk Management in Northern Irelandat riversagencyni.gov.uk
{{DEFAULTSORT:Flood Warning
Flood control
Hydrology
Warning systems