Tunnel in the Chilterns Area of Outstanding Beauty (AONB)?

With the first phase of High speed Railway 2 (Birmingham-London) being firmly voted through the House of Commons last month, the National Trust has handed in a petition (along with many others) expressing our concerns about the scheme and suggestions as to how it could be improved.

The most frequent request from petitioners is that HS2 ltd needs to build a “fully bored tunnel” for the railway throughout the whole of the Chilterns Area of Outstanding Natural Beauty (AONB). This idea is supported by many inhabitants in the Chilterns, conservation groups, MPs and local authorities.

It begs the question, what is an AONB and why does it deserve to be protected to this degree against the HS2?

HS2 will start construction in 4 years

HS2 will start construction in 4 years

What is an AONB?

Many of us would know our nation’s National Parks, which include Dartmoor and the peak District. These receive special protection from insensitive development and often have their authorities to protect them.

AONB’s were made equal status with National Parks in 2000. They are considered to be areas that need protection to preserve their beauty and ecology, although they often don’t have the same judicial weight as National Parks and don’t have their own authorities. This might explain why HS2 have not accepted demands for a fully bored tunnel as of yet.

What makes the Chilterns special?

This area was designated an AONB due to:

  • Landscape- HS2 would no doubt impede on the overall ‘natural beauty’ of this area which has not changed since medieval times
  • Ecology- many conservation groups have pushed for the protection of ancient woodland (see previous post) and many habitats that will be disrupted by HS2. Not to mention the ecological barrier the track would create where no wildlife could pass.
  • Noise- without proper mitigation tranquillity, in the Chiltern’s would be disturbed.
  • Cultural heritage- Some people have expressed concern over the railway’s impact upon archaeology and damage to previously undisturbed Iron Age earth structures (not to mention all the grade II listed farm houses that will have to be demolished)

How should we protect the Chilterns?

So it is clear the Chilterns has irreplaceable aspects that need we need to conserve, so what are our choices?


Bored tunnel

This option is the least disruptive way to build HS2 through the Chilterns AONB.

Of course tunnelling is the most costly scheme, but seeing as HS2 already plans to tunnel halfway through the Chilterns many argue that it should be extended to span the full AONB.

Click here for the useful HS2 route map from Chilterns Conservation Board.


 “Green Tunnel or Land Bridge”

The step down from a tunnel is the ‘green tunnel’ or ‘land-bridge’. This involves building embankments either side of the track, putting a lid on top, and placing earth and vegetation on top of that lid. (see last week’s post)

This reduces the impacts on ‘natural beauty’, noise and wildlife, and it is of course cheaper than boring straight into the ground.

However, as this landscaping scheme would be above ground it would still significantly disturb the landscape, ancient woodland and cultural heritage.

Click here for a clear illustrated guide to tunnels from the Woodland’s trust.


Cuttings, embankments and protective barriers

Failing all this, we then have other schemes to reduce the impact of the railway. Embankments and cuttings can partially protect the AONB from noise and visual impacts.

Noise barriers also will stop most of the noise from the railway but will need to be screened by trees to protect the landscape.

Of course, this sort of scheme will have the most negative impact on wildlife, ancient woodland and cultural heritage.

At the moment HS2 are using a combination of all these methods (see map) which many feel isn’t enough to protect the AONB. What do you think is enough to protect the Chilterns?


2 thoughts on “Tunnel in the Chilterns Area of Outstanding Beauty (AONB)?

  1. The Chilterns Conservation Board, whose remit is to protect the Chilterns Area of Outstanding Natural Beauty, firmly believes that if HS2 goes ahead, the only way to prevent the AONB from irreparable damage is to place the rail line in a bored tunnel under the whole of the AONB. We have said as much in our petition to the HS2 Hybrid Bill Select Committee.

    Just a couple of comments on what is written above. Under ‘What is an AONB’ the statement ‘AONBs could be considered the next step down from a National Park’ is unfortunate and inaccurate. The landscapes designated as AONBs are considered to be of equal value to those in National Parks – this was confirmed by the Countryside and Rights of Way Act 2000. AONBs and National Parks are protected to the same degree by law from insensitive development. The only difference is that the planning authority for a National Park is the National Park Authority whereas the planning authorities protecting AONBs are the local district/borough councils.

    You state that the Chilterns was designated an AONB under the recommendation of Natural England. This is not true – the Chilterns AONB was designated in 1965, many decades before Natural England existed! In fact, the designation of the Chilterns as an AONB was first mooted in the 1940s when the legislation which created the designations of AONBs and National Parks was being put together (the National Parks and Access to the Countryside Act 1949).

    The question that perhaps would have been more pertinent to ask above is why, when the Chilterns AONB is nationally-protected as one of the UK’s finest landscapes, is the Government ignoring its statutory duty to protect the Chilterns countryside and driving a huge infrastructure project through the heart of it?

    • Thanks for the feedback. Yes, you are right in that AONB’s are considered to be ‘equal’ since 2000 and that in the case of HS2 really don’t seem to be.

      This piece was merely to reflect upon the importance of the Chilterns and why people have chosen a fully bored tunnel when compared with other options.

      I will make the necessary amendments.


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