What are the alternatives?
There are several potential solutions to Oxford's flood challenges that combine hard and soft engineering approaches. We hope to explore a range of ideas that combine maximum flood protection for homes with respect for the environment to encourage solutions that are future-proof.
Moving Floodwater by Dr Rod Chalk - an alternative proposal
*(inclusion does not constitute endorsement. We aim to represent a range of views.)
Hinksey 1852 - Built on a floodplain, Oxford has a long tradition of flooding, even before climate change has accelerated the risk.
Flood events were common in the 19th century.
The flood of 1947 was the highest for the last 100 years.
The most devastating recent flood was 2007, which led to the search for a longer lasting solution.
This was just off the Botley Road in 2007
Why is there a flood problem? When the Thames bursts it's banks in Port Meadow, the water needs to find its way back to the flood plain, making it's way around the high ground of central Oxford by the shortest route.
The water follows follows the path of least resistance around the high ground of central Oxford
Human development has created obstructions. These include some of the main routes into Oxford, including the Botley Road and the Abingdon Road, which are vulnerable to flooding. Also the railway embankments and walkways such as Willow Walk and the Devil's Backbone.
The Oxford Flood Alleviation Scheme aims to address these blockages and pinchpoints with 3 main components. The first and most important component is the culvert widening at Redbridge pinch point. This has a modest cost and a large benefit.
The second component involves
constructing fixed flood defences or bunds.
The most controversial component of the scheme is the 3rd component, the channel or "lowered floodplain" that means digging out 700 thousand tonnes of gravel and alluvial soil from the existing flood plain.
The Oxford Flood Alleviation Scheme includes the design of a channel, which the Environment Agency refers to as a "lowered flood plain."
The "lowered flood plain" is a passive gravity driven system. This means it cannot be easily controlled and the shallow design of the channel limits the amount of water it can carry.
HOEG propose several alternative options and claim they would work as effectively.
The option presented here is the pumped pipeline scheme designed by Jonathan Madden. This is an active, enclosed pressure driven system.The flow of water in the pipe is fully controllable. At 44 cubic metres per second it will move more floodwater than the channel, but that's not the most important point.
The pipeline will operate at maximum flow as soon as river levels start to rise.That's important because it can function to flatten the curve making flooding less likely.
If you can start pumping at the beginning of a flooding cycle, you can potentially avoid the point here where property flooding occurs.
The pumped pipeline flows directly out into the Thames, reducing the risk of flooding in Kennington.
If floodwater enters faster than the pipeline can remove it, the natural capacity of the flood plain is still available. This is considerable and only when this has also been exceeded will property flood.
Moving water under pressure in pipes has been done since Roman times. A pipeline scheme has already been built at Pilmuir in Scotland.
Unlike the channel, it is 100 % predictable, it's reliable, and there are no engineering risks involved in pumping water
The pipeline replaces the channel but would be in addition to the fixed flood defences at Botley Road and South Hinksey.
The pumped pipeline is significantly cheaper than the channel, and most importantly causes no lasting environmental damage.
The trench in which the pipeline is buried will be back-filled. That means there is no spoil to remove.
Arguments for Considering a Pumped Pipeline from the Hinksey and Osney Environment Group
Why Does it matter?
If the environment is protected, there will be no objections from landowners, all of whom objected to the channel. There would be no public inquiry, meaning the flood scheme can go ahead immediately.
What does the EA say?
They have considered many options but prefer the channel option that is part of the current OFAS scheme.
What happens next?
Hinksey and Osney Environmental Group want a flood alleviation scheme along with all others who have concerns about the scheme. We don't want a public inquiry. But if the Environment Agency proceed with the channel regardless, landowners and residents will object to prevent irreversible environmental damage and force a public inquiry. The case for the channel will be questioned on economic, environmental, and on hydrological grounds.
We would ask the EA to re-consider.