River levels in Shrewsbury have been monitored for many years at the Welsh Bridge. The historical data shows that the level of the river has varied greatly over time, with some periods of high flooding and some periods of low water levels.
Since monitoring began, 90% of the time the normal range for the River Severn at the Welsh Bridge is between 0.42m and 2.70m. However, in recent years there have been some significant rises in river levels, with the highest level recorded was 5.25m in November 2000.
Where does the River Severn come from?
The source of the River Severn is in Wales’ Cambrian Mountains on the exposed slopes of Plynlimon, which is less than 15 miles from the Welsh coast. The average rainfall for this area is high ( -2500mm), occurring at an elevation of 610m above sea level.
At this point, the Severn is not even a trickle, it’s just a peat bog that soaks up the rainwater. The water trickles from the bog to form a small brook that’s then fed by a number of tributaries eventually becoming the River Severn we know and love in Shrewsbury.
The first important tributary can be found upstream from the market town of Llanidloes and is called Afon Dulas. The Afon Clywedog then joins in the town itself. Upstream of Caersws the Afon Cerist joins the river until we reach Newtown where Mochdre Brook enters the equation followed by Bechan Brook. More tributaries add along the route including The Mule, River Rhiw and Camlad before the Sylfaen Brook enters at Welshpool and the Bele Brook near Arddlin.
Probably the most significant tributary is the River Vyrnwy. Its source, Lake Vyrnway is a dam, where the headwaters are controlled. This presents a major issue when flood alters are raised in Wales, as the water is then released downstream. Before the River Severn reaches Shrewsbury three more major tributaries join, these are the River Perry, Rad Brook and Rea Brook.
What causes the river flooding in Shrewsbury town centre?
The River Severn is Britain’s longest river and also the country’s most powerful, with a catchment area of -5000 square miles. It drains an area of South Wales, the Midlands and parts of North West England.
In general, the river level is highest in winter and early spring due to heavy rainfall and snowmelt from the Cambrian Mountains. The flow rate can increase from an average of -3500 cubic feet per second to over 200,000 cubic feet per second.
This high level of water can cause problems for towns and villages located next to the river, as there is a risk of flooding. Shrewsbury is one such town, situated as it is on a loop in the river.
Heavy rainfall in the catchment area upstream
Groundwater seepage is also a major issue when it comes to flooding. The high water table means that the ground is often saturated, and any water that falls on the surface will quickly flow into the river. Typically in Winter we see a rise in the water table due to the high rainfall and snowmelt.
Releases from Lake Vyrnwy
River Vyrnwy is a man-made reservoir located in Powys, Wales. The lake was created in the late 19th century for the purpose of supplying Liverpool with water. It has a capacity of 59.7 gigalitres of water and is fed by 311 brooks, waterfalls and rivers.
When flood warnings are issued by the Environment Agency in Wales, water is released from the reservoir to try and reduce the risk of flooding. This can have a significant impact on the river level in Shrewsbury, as the water flows downstream.
The impact of river levels in Shrewsbury
Flooding in Shrewsbury is a major problem and one that has caused a great deal of damage to the town over the years. In 2000, the town was hit by floods that caused an estimated £100 million pounds worth of damage. The town centre was particularly badly affected, with many shops and businesses being forced to close for several months.
More recently, the town has been hit by floods on an annual basis. The damage is less severe thanks to early flood warnings, accurate flood alerts and improved flood defences, but still, it causes a great deal of disruption to businesses and residents.
The risk of flooding in Shrewsbury is set to increase in the future as a result of climate change. Heavy rainfall is likely to become more frequent, and this will increase the risk of river flooding. This is obviously a problem for both Shropshire Council & the Environment Agency, but what can be done?
Preventing the River Severn flooding in Shrewsbury
While the River Severn is prone to flooding, there are a number of things that can be done to try and reduce the risk. These include:
Building raised flood defences
One way to reduce the risk of flooding from River Severn is by building raised flood defences. Shrewsbury council alongside the Environment Agency already have a robust defence system that uses walls and temporary barriers that run near along Frankwell riverside.
These flood defences work wonders at keeping the River Severn from flooding the area surrounding the Theatre Severn. However, the tributaries are also swollen, meaning other parts of the town experience widespread flooding with flood water entering homes, causing power outages and significant damage. Areas particularly hard hit in the town centre include the areas near Abbey Forgate Car Park, Gravel Hill Lane, Sydney Avenue and Coleham Head.
In addition, flood water comes up through the sewer and drain system and onto the roads in the town centre, leaving only Greyfriars Bridge and the Welsh Bridge as crossing points for people to enter the town.
Flood defences help to keep the river at a manageable level, but it doesn’t solve the problem, often it just moves the problem further down the river.
Managing water releases from Lake Vyrnwy
As we have seen, water releases from Lake Vyrnwy can have a significant impact on the river level in Shrewsbury.
To try and reduce the risk of flooding, the amount of water released from the reservoir can be managed. This can be done by controlling the amount of water that flows into the reservoir, and by releasing water at a slower rate.
The Environment Agency already tackle this issue head-on, but still the River Severn floods.
Improving drainage in the catchment area
Another way to reduce the risk of flooding is by improving drainage in the catchment area. This can be done by clearing blockages from drains and culverts, and by constructing new drains to improve the flow of water away from built-up areas.
It is also important to ensure that there is enough green space in the catchment area, as this can help to absorb water and reduce the risk of the River Severn flooding.
Keep up-to-date with the river levels in Shrewsbury
Flooding is a major problem in Shrewsbury and one that is set to become more severe in the future as a result of climate change.
The Environment Agency is working on a number of schemes to protect the town from flooding, but there is still a risk that properties and businesses could be affected.
If you are concerned about the risk of flooding, you can check the latest river level data here or sign up for flood warnings.
In Shrewsbury, the River Severn levels are monitored at the Welsh Bridge. At this monitoring station, the normal level of the River Severn is between 0.5m and 2.52m. The highest level ever recorded was on Wednesday 1st November 2000 when the River Severn at the Welsh Bridge reached 5.25m.
The best place to find the most up-to-date information on River Severn levels is via the Environment Agency website.