HOW DRY CONDITIONS CAN LEAD TO SEVERE FLOODING

Following a period of hot and dry weather, why have we seen such dramatic flooding? After weeks of drought conditions during the height of summer, we have seen the weather change rapidly to long and heavy showers which can have significant impacts on people and property.

July was a particularly hot, dry month. Temperatures exceeded 40°C for the first time on record and several wildfires were recorded. It was the driest July across England since 1935 and the driest July on record for East Anglia, southeast and southern England. From January to July 2022, the UK had experienced just 69% of the average rainfall levels, which led to a drought status in 8 of the 14 areas in England.

However, this period of dry weather shifted in mid-August. Low pressure systems began to dominate our weather, resulting in significant spells of rain and reports of thunderstorms which have been observed across the country over the past week. This sharp transition from excessively dry conditions to wet weather often leads to flash flooding and the pooling of water. But why is this the case, when the ground is at its driest and starved of water?

The drying of soils causes them to harden and become less receptive to the absorption of water, which leads to far higher levels of run off. This video features an experiment carried out by University of Reading meteorologist

Dr Rob Thompson, which shows the effects a heatwave can have on soil absorption rates. This process is exactly what we have witnessed over the past week, with examples of flooding across many regions of the country. Worksop in Nottinghamshire recorded 93mm of rainfall during a three-hour period between 5pm and 8pm on Tuesday 16th August 2022, almost twice the average monthly rainfall of 54mm. This combination of unusually high levels of rainfall and extremely dry ground conditions caused flash floods which affected at least 30 homes and business premises in the region. In addition, an eight-foot-wide sinkhole was reported in a Matalan car park.

Flash flooding was also observed in the south of the country, resulting in train station closures and flooded roads in London. Similar conditions were also noted in Kent and Sussex. In addition, heavy rain overwhelmed sewage systems, leading to pollution warnings at more than 40 beaches and swimming spots in England and Wales.

Landmark Information Group use modelled data from leading flood risk data providers, including JBA Consulting, the Environment Agency and Geosmart to identify areas potentially at risk of flooding from several sources (including river, coastal, surface water, and groundwater).

Potential depths and extents of flooding are used to determine risk ratings for a given property/site. This data is checked and corroborated by a qualified consultant at Argyll Environmental to inform you of the potential risk from flooding. We cannot reiterate how important this is to a flood risk assessment. When providing a risk assessment for a property, data should of course inform the decision, however a qualified consultant should make it.

To those that think all flood assessments are the same, the Law Society specifically warns in their practice note that this is simply not the case.

As consultant assessments are much more accurate than automation, our flood reports are not fully automated. This is at no extra cost to your clients and built into our processes to also stop any delays. Only from Landmark do you get this level of service, interpretation, and accuracy for residential flood searches.

Why not ask your current supplier this simple question, “Does a consultant look at the flood assessment in your report before you send it to me?”

If you are not using Landmark for your flood assessments and you want to understand more, click here.