Computers and Floods (After the Deluge)

Date/Time:
Wednesday 12 April & Thursday 20 April 2006

Description:

Due to the size and layout of the Environment Agency (EA) incident room numbers were limited to ten people. The EA kindly agreed to host two visits; Margaret Moore attended the one on 12th April 2006, hosted by Ron and Laura, whilst Malcolm George attended the one on 20th April 2006, hosted by Colin Atkinson. This report summarises both visits.

Background

There are three areas in the North East region – Northumbria, Dales (York) and Ridings (Leeds). In the Dales area the catchment areas involved are Tees, Swale, Ure, Nidd, Wharfe, Ouse, Esk, Derwent and North Sea. Catchment areas divide into tables which sub-divide into areas.

Telemetry

On the wall of the incident room was a huge 1:50,000 map of the region with dots to indicate telemetry spots. Red dots indicate that the telemetry is alarmed; if it is a “floor” measurement then the alarm is sent to hydrologists otherwise it is a “level” measurement and those alarms are sent to people concerned with flood issues. For the purposes of our visits we dealt with “level” measurements. Measurements are taken and automatically sent by telemetry every 15 minutes.

When the duty officer in the regional office gets an alert from telemetry he / she monitors the appropriate catchment area. Should the situation worsen then he/she telephones the local duty officer. The officer can click on an area (a sub-division of a table - see above) to view its status in a symbolic representation e.g.

Over and above the 15 minute update of levels via the automatic telemetry, the duty officer can poll (dial-up) and get the latest reading whenever necessary.

It is also possible to produce graphs of how the levels have varied over time with a dotted reference line representing the “high” level and another line representing the forecast (if available) as well as the actual level. The officer can then home in on the forecast (see below).

A series of colour-coded T cards gives a visual over-view and indicates which area to watch next. Each catchment area is represented by a colour e.g. Tees are pink cards. When there is an alert the “top” card of that catchment area is moved into the active area. Cards cascade across in “logical” order for a “well-behaved” flood (one that progresses downstream in sequence) as the flood water proceeds downstream.

There is a second set of colour-coded T cards for the operations department.

Water level forecasts

These are based on modelling which is constructed regionally. They are the remit of the forecast duty officer (FDO) who uses information from the Met Office (information on surges, storms, winds and from wave buoys). The scheduled forecast runs look about 12 hours ahead. The time at which the water level will peak is forecasted twice daily routinely and by request during an event.

The forecast is represented very graphically (green implies normal then yellow, amber and red) as speed and ease of assimilation of information are paramount.

Also in the incident room is a computer with a line to the Met Office which accesses HYRAD (the weather forecasts). The duty officer actually has access to the information for England but generally views the area from north of Newcastle to well south of the Humber estuary. He / she can also zoom in on one catchment area at a time.

The map is colour coded in rainfall (mm/hour). The forecast “runs” in 15 minute intervals up to 12 hours ahead. (This is rather like the weather forecasts that we see on television but with the positions of the weather fronts etc. being shown at 15 minute intervals rather than e.g. by 8am then by noon.) This data has already been analysed by the Met Office. If necessary the officer can look at raw data up to 36 hours ahead but this would need analysing.

Combining forecasts and telemetry

The duty officer can add in scenarios to the forecast levels, e.g. if expecting a surge from the sea and/or high winds, and look to see what effect this will have on the forecast levels. However, many other things can happen that affect the actual levels that occur. Local knowledge of the duty officers is very helpful in such situations. For example:

  • Water can join a river between telemetry stations, causing unexpected peaks at the station downstream.
  • A sudden localised downpour will affect everything downstream. This type of thing will have a greater impact if the ground is already wet - or very dry - as the water will not be absorbed.

(The floods in November 2000 were unusual in that the heaviest rainfall was not in the upper reaches, which would have alerted the EA by being fed in via the monitoring systems, but fell in the lower reaches of the rivers and the subsequently flooded areas themselves. In fact some of the monitors in the upper reaches didn’t rise much above seasonal norms during the whole period.)

The duty officers have laptops at home and can do all the above from home – but it is slower and ties up the phone line so they often open the incident room. The duty officer is involved in lots of operational work, directing men on the ground.

Alerts system - Floodline Warnings Direct (FWD)

A new alerts system, which is GIS based, had just gone live. The target area is based upon local knowledge of places that flood frequently.

There is also a map with shaded areas. The shaded areas give the 1000 year outline assuming that there are no defences; this is based on LIDAR (LIDAR - aeroplane shows the height of the land in a grid 10m2). The EA usually warn people with a 100 year risk. Residents in the area can self-register and keep their details up to date.

The alerts can be issued via a number of channels, being telephone, fax, mobile, SMS or email or a combination and this can be configured for each residence. Each method chosen has its own time frame. The system tries each method (that is appropriate for the time of day) several times then tries the next contact sequence e.g.

  • home 17:00 - 09:00 contact sequence 1
  • work 09:00 - 17:00 contact sequence 1
  • mobile 00:00 - 24:00 contact sequence 2

The officer can set up the message using text to voice conversion which can be amended phonetically (for local dialects etc.).

Warning times vary depending upon the current situation and the geography of the area. For example, the Derwent is slow to rise and slow to clear so usually gets plenty of warning. By contrast, places at the head of a steep valley have levels which rise very quickly so it is harder to give a lot of warning.

Both groups found their visit very interesting and informative. There is a mix of technologies employed, forming a system which quickly gives the duty officer the information that is needed in an emergency - and routinely.