SEPA guidance on current severe weather situation
Any flooding updates will be posted on Floodline. People can help to reduce potential problems around their own properties, for example by checking that ice isn’t blocking drains, and clearing it if safe to do so.
More information on the forecast over the next few days can be found on the Met Office website .
Further advice on dealing with the current weather conditions is available from the Scottish Government's Ready Winter webpage .
SEPA communicates the risk of flooding to the public, our partner organisations and through the media. Find out more on how we do this here.
Will it flood when it thaws?
Despite the recent thaw there is likely to be substantial snowpack remaining when the colder weather reasserts itself during the week and the pattern of the eventual thaw of lying snow will depend very much on the weather at the end of the colder spell.
A slow rise in daytime temperatures alone will mean that any thaw is likely to be gradual and result in no more than minor spates, localised flooding and daily fluctuations in water levels. However, if unsettled Atlantic weather systems move in, bringing a rapid rise in temperature and heavy rainfall, there is the potential for flooding in some areas, depending on the nature and extent of the snow cover.
SEPA continues to work closely with the Met Office, emergency partners and Scottish Government regarding forecasts of any change which may herald incipient flooding problems.
If you are concerned about flooding, live flood updates are available via Floodline on 0845 988 1188 or online. SEPA has also published guidance on preparing for flooding and if you are a victim of flooding, what to do and who can help .
Snowmelt and Flooding
After an extensive and deep fall of snow, there is always a risk of flooding. Recent snow in Scotland has, in places, been as deep as 50 cm. When this amount of fresh snow melts it releases about 50mm of rainfall equivalent, which is what might be experienced in a pretty severe rainstorm. So if the melt were to occur in a single day then it may lead to flooding, but if it is spread over several days then flooding from rivers will be unlikely.
Thawing of snow depends on several factors:
- temperature obviously;
- but also wind speed, since in calm conditions the air near the snow surface will chill down and not cause much melting;
- cloud cover and sunshine, since sun will melt snow but cloud cover can also prevent frosts and therefore encourage melting at night;
- humidity of the air is also significant since condensation on the snow surface from warm, moist air will increase thawing quite a bit;
- rainfall is absolutely crucial since it not only adds more water but very much encourages rapid rates of melting;
- and, finally, the nature of the snowpack itself affects thawing - light, uncompacted snow, or snow that has a dirty surface will often melt much quicker than snow which has become more solid and icy.
As melt occurs then the state of the underlying soil also matters. If it is frozen then meltwater, with or without additional rainwater, will run straight off the surface and into rivers. If it is not frozen, then the meltwater will seep gradually into the ground and river levels will rise more gradually and not reach such a high peak.
So predicting river levels or flooding, when snow is melting, is quite a tough challenge!
To add to the difficulties of predicting where flooding will occur as a result of the thaw we also need to consider localised and unusual causes, such as 'ice damming'. Most rivers, burns and streams across Scotland now have considerable ice cover on them. When the thaw begins, river levels will start to rise and the ice will break up. Large quantities of ice will be transported downstream and may accumulate on bridges, culverts and river banks potentially causing a 'bottleneck' to river flow and increasing the local flood risk. Such occurances are not predictable, even in locations where we operate flood warning schemes.
A rapid thaw is usually occasioned by a sharp rise in temperature (typically 0-15C) linked to significant rainfall causing a sudden collapse of the snowpack in a short period of time.
A slow thaw usually results from a more modest rise in temperature (typically 0-7C) with little or no additional rainfall and may often be extended over several days or more.
So terminology too can be tricky!
SEPA Flood Warning Systems
SEPA monitors water levels in rivers and lochs continuously and uses this information along with forecasts and models to issue alerts when necessary. SEPA's flood warning infrastructure and software systems remain fully operational.
The latest information will continue to be posted on Floodline.
What can be done with snow that has been cleared from streets or put into heaps?
- Relatively clean snow can be disposed of adjacent to a river, subject to the guidelines below:
- Particular care should be given to the siting of snow heaps. Snow should not be placed directly into the flow of the river as snowmelt will be slow and there may be a risk of flooding and erosion of river banks. Snow should therefore be placed adjacent to the river on the river bank
- Careful consideration should be given to the placing of snow heaps close to bridges or buildings so that flood risk is avoided.
- Snow heaps should not be placed on opposite banks at the same location on a river. This is to avoid a possible bottle-neck effect constricting river flows.
- It may be appropriate to dispose of snow into tidal waters. Any adverse impact on boats, ships or bridges should be taken into account when selecting the disposal site.
- When snow disposal activity is being carried out careful management of the site should take place to ensure that these guidelines are followed.
Snow with high levels of salt and grit should be stored on suitable land at least 30 metres away from watercourses and drains and tidal waters.
SEPA will provide advice on specific sites/issues as required. Please contact your local SEPA office.
Removal of beach sand for gritting purposes
Marine Scotland and SEPA do not promote the use of beach sand. As an alternative we would recommend that local sand and gravel quarry operators should be approached. In the event that beach sand is being considered, permission should be sought from the appropriate landowner and Marine Scotland should be contacted for advice, using the contact details below.
Email (office hours): MS.EnvironmentalProtection@scotland.gsi.gov.uk
Email (out of hours): Spillresponse@marlab.ac.uk
Tel. No (office hours): 01224 876544
Use of De-icer on roads
SEPA is working closely with Transport Scotland on the possible use of alternative de-icers (to the traditional sodium chloride based de-icer) during extreme cold weather events. SEPA understands that Transport Scotland’s contractors may wish to use alternative de-icers where certain scenarios arise. If further information is required please contact Phil Leeks in SEPA’s Water Unit on 01786 457700.
Slurry, Milk and Manure – some of the pressures facing livestock farmers during the current adverse weather conditions
Farmers are already facing problems with slurry, milk and manures as a result of the recent extreme weather conditions being experienced across Scotland. Snow and frozen ground conditions across the country have already caused issues for many, and as the thaw sets in the problems facing livestock farmers could be exacerbated as field conditions go from one extreme to another and the ground becomes waterlogged. Snow melt and leakage from burst water pipes can also enter slurry stores, adding to already difficult working conditions.
The Diffuse Pollution General Binding Rule (DP GBR 18) for the storage and application of fertilisers to reduce diffuse pollution makes it clear that slurry and milk must not be spread on snow-covered, frozen or waterlogged ground - although manures can be spread on frozen ground outside NVZs.
SEPA has been in discussion with NFUS and has recognised that, where stores are full, a farmer may have little choice but to spread slurry, milk or manure on unsuitable ground and in poor conditions. Before milk which cannot be collected is spread on land, we would recommend transfer to the farm's slurry system, although we realise this may not be practical if the slurry store is full.
We would stress that farmers should not dispose of milk down farm surface water drains due to its extremely polluting nature and ask that all farmers contact their local SEPA office to discuss what options are available to them before spreading anything on land.
Please click here to find out if your local SEPA office has been affected by the weather.
Last updated: 28 December 2011