Public Articles

  • Public Article 1

    Correcting the Environment Agencies Published Flood Map.

Early in 2016 the Environment Agency met its government driven deadline by publishing flood related information to every home around the country. After that event, locals of Much Wenlock were suddenly made aware that they may live in a property that someone declared MAY flood!

It seems that there is a standard way of marking a 2 dimensional map with a "BLUE COLOURED BOUNDARY" in a potential flood plain area. So the Agency marked the map accordingly. This surprised local householders that are some 3-5 metres in height above the flood plain. So much so that local newsletters published complaints, the local civic society ordered a special council meeting to discuss the matter, county council officers have been emailed requesting their involvement.

It is all a bit "up in the air".

So your local flood group have taken up the baton and will seeking to clarify the following:-

1) Try to ensure that a clear and accurate flood map is published (correct current erroneous maps).

2) Determine under what rainfall conditions the potential indications of flood depths are based upon.

3) Home owner expectations - (personal flood plans, home flood prevention possibilities).

4) Household Insurance implications to be clearly identified.

5) Improve awareness of available information to local home owners concerning surface water flooding.

So what is it all about - look below to see what the currently published flood map for Much Wenlock looks like, and yes it is wrong! The Shilte river DOES NOT FLOW DOWN THE HIGH STREET! Also the Sytche lane tributary is missing and that has its own flood zone which is not shown! This is our first problem get the MAPs corrected.

The Current Map

Click here to see the current version of the MAP shown above (last checked 25/02/2017).

How do I understand what it all means? Read this extract from the Environment Agencies web site explaining how to understand what it all means.

Understanding The Current Map

Note in this explanation "WHITE" = minimal problems but "LIGHT BLUE" indicates and increased possibility of some problems. The actual first line on the page reads: "The location you have selected is in an area that has a very low chance of flooding from surface water" and that is what caused a stir when you look at the next map. Remembering that "very low" would be a white colour and a medium dark blue would be a "medium risk".

OK - So? Whats wrong with that, apart from the river not flowing down the High Street what is wrong? It is all in white with a blue line showing the river?

Well thats a good question. So now let us add in the possibility from flooding by SURFACE WATER (overland flows). It is on this map where the fun starts. You will note that on this map the Shilte rivers path is correctly annotated and shows as flowing down the back lane. On this map there is a lot more "BLUE" and many householders were quick to point out that if the MAP was in 3D and at a higher resolution it might be more obvious what property could be flooded or not. At this point we also need to know expected possible depths based upon modelled rainfall for a given time period. This information is not available on these maps. This is our second problem to get correctly represented.

Surface Flows Added

Let's be fair this was a good first attempt to map the local flooding issues. Unfortunately it is at its highest resolution on this mapping model. So improvements were needed. So that you understand, in following two pictures the "High" or dark blue represents a depth greater then 900mm (almost three feet deep), the medium (lighter blue) is around 300mm to 900mm (one to three feet deep) and the low (very light blue) is anything less than 300mm (one foot) deep. In this diagram white (very low risk) is around 20-50mm (1-2 inches) deep, which is considered to be normal surface runoff in a storm situation.

Later in the year the Environment Agency improved their tool kit and published a map of a higher resolution modelled scenario. Now take a look at this map that was sent via Royal Mail to the people of Much Wenlock and was published on the Environment Agencies web site. Yes this shows a lot more BLUE area potentially under water.

Current Flooding Extents

The above screen shot is a familiar picture which may have been released to all potential houses that could be threatened by overland flooding in this area. In the next shot we expand a sample of this picture to its maximum. If this model is accurate we really need to know the parameters for which this map represents.

Maximised Flood Map

Click here if you believe your property may be at risk from surface water flodding, you can find this tool at this location.

To use the tool you will need to select DETAILED VIEW. Then find Much Wenlock by zooming in, when you have found it select a view from the left hand menu, try surface water flooding, extent of flooding view. Try it.

So how do we stop or deal with all of these overland flows to stop local residents from being flooded when the next big storm hits? Well, read on, dive further into this web-site for the next steps forward - look in the public projects section.

So watch this space for more details, your local flood group have work to do.

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