Flood warning
Encyclopedia
Flood warning is closely linked to the task of flood forecasting
. 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about whether warnings of floods should be issued to the general public or whether previous warnings should be rescinded or retracted.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 decisions made by someone responsible for initiating flood warnings must be influenced by a number of factors, which include:
A computer system for flood warning will usually contain sub-systems for:
, the UK Met Office
may issue warnings of flooding likely to occur because their meteorological forecasts of rainfall indicate that heavy rainfall will occur - such forecasts might be available 6 to 24 hours or more before the predicted rainfall, but are not fully reliable as to whether or precisely where such rainfall will occur. Thus such warnings would need to appropriately cautious and would have to apply to wider regions than will eventually be affected by the heavy rainfall. In conjunction with this service, more location-specific flood warnings are the role of the Scottish Environment Protection Agency
(covering Scotland) and the Environment Agency
(covering England and Wales) who undertake flood forecasting tasks over shorter lead-times, on the basis of:
In the UK, the dissemination of flood warnings is moving or has moved towards a service whereby those potentially at risk of river flooding can pre-register to receive warnings by phone from an automatic system. Both warnings and updates about current conditions are also carried by local radio stations. In addition, internet sites have pages showing what 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 does issue weather warning. Flood risk management is the responsibility of Rivers Agency
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 National Weather Service
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 Watches
and Warnings
are issued.
In the USA and Canada
dissemination of flood warnings is covered by Specific Area Message Encoding
(SAME) code FLW, which is used in the US Emergency Alert System
and NOAA Weatheradio
network and in Canada's Weatheradio Canada
network.
"Flood Statements" are issued by the National Weather Service
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.
THE SOUTH CHICKAMAUGA CREEK AT CHICKAMAUGA TN
AND CREST NEAR 19.0 FEET AROUND 2 AM TUESDAY. THE RIVER WILL FALL
BELOW FLOOD STAGE TUESDAY AFTERNOON.
TRAFFIC. WEST CHICKAMAUGA CREEK OVERFLOWS ITS BANKS NEAR THE
GEORGIA STATE LINE AND INUNDATES SEVERAL ROADS AND PROPERTIES IN
THE AREA.
$$
PRECAUTIONARY/PREPAREDNESS ACTIONS...
MOST DEATHS IN FLOODS OCCUR IN CARS! IF YOU COME TO A CLOSED OR
FLOODED ROAD, TURN AROUND! DON'T DROWN! FOR MORE DETAILS, STAY TUNED
TO NOAA WEATHER RADIO OR COMMERCIAL TELEVISION OR RADIO THAT CARRY
WEATHER INFORMATION.
&&
$$
TD
Source:
FLOODING TO CONTINUE.
TUESDAY AFTERNOON. THE RIVER WILL FALL BELOW FLOOD STAGE LATE
WEDNESDAY MORNING.
EVACUATED. EVACUATIONS ALSO TAKE PLACE AT THE FOUNTAINBLEAU
APARTMENTS ON SPRING CREEK ROAD IN EAST RIDGE.
$$
$$
BOYD
Source:
Flood forecasting
Flood forecasting is the use of real-time 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 watershed or river basin. Flood forecasting can also...
. 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.
Description
The task of flood warning can often be 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 forecastingFlood forecastingFlood forecasting is the use of real-time 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 watershed or river basin. Flood forecasting can also...
; - 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.United Kingdom
For example, in the UKUnited Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, the UK Met Office
Met Office
The Met Office , is the United Kingdom's national weather service, and a trading fund of the Department for Business, Innovation and Skills...
may issue warnings of flooding likely to occur because their meteorological forecasts of rainfall indicate that heavy rainfall will occur - such forecasts might be available 6 to 24 hours or more before the predicted rainfall, but are not fully reliable as to whether or precisely where such rainfall will occur. Thus such warnings would need to appropriately cautious and would have to apply to wider regions than will eventually be affected by the heavy rainfall. In conjunction with this service, more location-specific flood warnings are the role of the Scottish Environment Protection Agency
Scottish Environment Protection Agency
The Scottish Environment Protection Agency is Scotland’s environmental regulator. Its main role is to protect and improve Scotland's environment...
(covering Scotland) and the Environment Agency
Environment Agency
The Environment Agency is a British non-departmental public body of the Department for Environment, Food and Rural Affairs and an Assembly Government Sponsored Body of the Welsh Assembly Government that serves England and Wales.-Purpose:...
(covering England and Wales) who undertake flood forecasting tasks over shorter lead-times, on the basis of:
- observed rainfall over the recent past;
- forecasts of rainfall over lead-times of up to about 6 hours;
- current and past river conditions.
In the UK, the dissemination of flood warnings is moving or has moved towards a service whereby those potentially at risk of river flooding can pre-register to receive warnings by phone from an automatic system. Both warnings and updates about current conditions are also carried by local radio stations. In addition, internet sites have pages showing what 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 does issue weather warning. Flood risk management is the responsibility of Rivers Agency
Rivers Agency
The Rivers Agency is an Executive Agency of the Department of Agriculture and Rural Development . It is the statutory drainage and flood defence authority for Northern Ireland. DARD is the competent authority for the implementation of the EU Floods directive and has deligated the day to day...
in Northern Ireland. Consideration will be given to the introduction of a warning system as part of the implementation of the EU Floods directive
Floods directive
DIRECTIVE 2007/60/EC of the European Parliament and of the Council of 23 October 2007 on the assessment and management of flood risks is commonly known as the ‘Floods Directive’....
.
United States
In the USUnited States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, the National Weather Service
National Weather Service
The National Weather Service , once known as the Weather Bureau, is one of the six scientific agencies that make up the National Oceanic and Atmospheric Administration of the United States government...
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 Watches
Flash flood watch
A Flash flood watch is issued by the National Weather Service when conditions are favorable for flash flooding in flood-prone areas where grounds are already saturated from recent rains....
and Warnings
Flash Flood Warning
A Flash Flood Warning is issued when a flash flood is imminent or occurring in the warned area. A flash flood is a sudden, violent flood after a heavy rain...
are issued.
In the USA and Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
dissemination of flood warnings is covered by Specific Area Message Encoding
Specific Area Message Encoding
Specific Area Message Encoding or SAME is the protocol used to encode the Emergency Alert System and NOAA Weather Radio's SAME Public Warning System in the U.S...
(SAME) code FLW, which is used in the US Emergency Alert System
Emergency Alert System
The Emergency Alert System is a national warning system in the United States put into place on January 1, 1997, when it superseded the Emergency Broadcast System , which itself had superseded the CONELRAD System...
and NOAA Weatheradio
NOAA Weather Radio All Hazards
NOAA Weather Radio All Hazards is a network of radio stations broadcasting continuous weather information directly from a nearby National Weather Service office. It is operated by the NWS, an agency of the National Oceanic and Atmospheric Administration within the United States Department of...
network and in Canada's Weatheradio Canada
Weatheradio Canada
Weatheradio Canada, in French Radiométéo Canada, is a Canadian radio network that broadcasts weather information. Owned and operated by Environment Canada's Meteorological Service of Canada division, the network transmits in both official languages from 199 sites across Canada.In most locations,...
network.
"Flood Statements" are issued by the National Weather Service
National Weather Service
The National Weather Service , once known as the Weather Bureau, is one of the six scientific agencies that make up the National Oceanic and Atmospheric Administration of the United States government...
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
608
WGUS44 KMRX 210433 CCA
FLWMRX
BULLETIN - IMMEDIATE BROADCAST REQUESTED
FLOOD WARNING
NATIONAL WEATHER SERVICE MORRISTOWN, TN
1233 AM EDT MON SEP 21 2009
...THE NATIONAL WEATHER SERVICE IN MORRISTOWN, TN HAS ISSUED A FLOOD
WARNING FOR THE FOLLOWING RIVERS SOUTH CHICKAMAUGA IN GEORGIA...
TENNESSEE...
SOUTH CHICKAMAUGA CREEK NEAR CHATTANOOGA TN AFFECTING CATOOSA AND
HAMILTON COUNTIES
HEAVY RAINFALL SUNDAY EVENING OF AROUND 3 INCHES IN THE CHATTANOOGA
AREA HAS CAUSED THE SOUTH CHICKAMAUGA CREEK TO RISE RAPIDLY.
GAC047-TNC065-211821-
/O.NEW.KMRX.FL.W.0013.090921T0433Z-090922T2200Z/
/CHKT1.1.ER.090921T0421Z.090922T0600Z.090922T1600Z.NO/
1233 AM EDT MON SEP 21 2009
THE NATIONAL WEATHER SERVICE IN MORRISTOWN, TN HAS ISSUED A
- FLOOD WARNING FOR
THE SOUTH CHICKAMAUGA CREEK AT CHICKAMAUGA TN
- FROM THIS MORNING TO TUESDAY EVENING.
- AT 11:15 PM SUNDAY EVENING THE STAGE WAS 13.0 FEET.
- MINOR FLOODING IS FORECAST.
- FORECAST...THE RIVER WILL RISE ABOVE FLOOD STAGE AROUND 7 AM MONDAY
AND CREST NEAR 19.0 FEET AROUND 2 AM TUESDAY. THE RIVER WILL FALL
BELOW FLOOD STAGE TUESDAY AFTERNOON.
- AT 19.0 FEET...WATER ACROSS MACK SMITH ROAD BEGINS TO IMPEDE
TRAFFIC. WEST CHICKAMAUGA CREEK OVERFLOWS ITS BANKS NEAR THE
GEORGIA STATE LINE AND INUNDATES SEVERAL ROADS AND PROPERTIES IN
THE AREA.
$$
PRECAUTIONARY/PREPAREDNESS ACTIONS...
MOST DEATHS IN FLOODS OCCUR IN CARS! IF YOU COME TO A CLOSED OR
FLOODED ROAD, TURN AROUND! DON'T DROWN! FOR MORE DETAILS, STAY TUNED
TO NOAA WEATHER RADIO OR COMMERCIAL TELEVISION OR RADIO THAT CARRY
WEATHER INFORMATION.
&&
$$
TD
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:
External links
- Environment Agency (EA) Flood Watch (live warnings) - England/Wales at environment-agency.gov.uk
- EA scheme description at environment-agency.gov.uk
- Scottish Environment Protection Agency (SEPA) Live Flood Warning Information at sepa.org.uk
- Flood warning for Ireland (Eire) at flooding.ie
- Flood Risk Management in Northern Ireland at riversagencyni.gov.uk