Calculating RPAs of extensive hedgerows

[Calibre_Consultancy]

Hi all,

 

Just a quick query with regards to a clients wanting hedgerow RPAs. If your TOPO has the hedgerow extents plotted and in some cases the hedgerows centre lines, do you just get yourself an average DBH for the whole hedgerow and measure the RPA from the centre line of the hedgerows?

 

I ask because obviously the width of the hedges will in many cases be much further out from the stems than the RPA radius and also just because you have a centre line, this doesn't represent where the hedgerows stems actually lie and therefore the RPA would be inaccurate in places because the stems are all over the place.

 

Or do people just place the RPA lines in line with the extents of the hedge itself?

 

If anyone can answer this for me it would be much appreciated!

[AA Teccie (Paul)]

Just a thought out loud here, as most development usually takes place on one side of the hedgerow only, and hence the other side is undisturbed, that would hopefully mean either the crown spread or half-height scenario would suffice...appen.

 

That said not as a practitioner but a theorist

 

cheers..

Paul

[Calibre_Consultancy]

Ya.. In this case the hedgerows are in the middle of the plot, they are to be retained and the proposal designed around them.... and the retained trees obviously.

 

Is it me or is this not covered somewhere in 5837 ..... I couldn't find it in there.

 

Thanks

Edited July 9, 2014 by Calibre_Consultancy

[AA Teccie (Paul)]

Ya.. In this case the hedgerows are in the middle of the plot, they are to be retained and the proposal designed around them.... and the retained trees obviously.

 

Is it me or is this not covered somewhere in 5837 ..... I couldn't find it in there.

 

Thanks

 

Sorry, shudda checked there first see p.7 sect. 4.4.2.7&.8

 

Paul

[Calibre_Consultancy]

Yes thanks I had already read that section and have recorded the dimensions as per the regs but then it says collect this info to ensure that the constraints can be fully assessed. No specific mention of RPA calculation which is itself a constraint ???

 

Im just assuming that the extents of the hedge is more of a consideration as a constraint than the RPA calculated from DBH

Edited July 9, 2014 by Calibre_Consultancy

[daltontrees]

There's only one issue here, and that is how much of the roots and soil need to remain undisturbed to ensure the ongoing vitality of the trees. RPA is just a first guess, and a relatively easy way out. If the simple RPA method is not appropriate, for whatever reason, it's up to you to satisfy the Council that any encroachment into the rooting area (not the RPA) will not damage the survival of any of the trees.

 

The centre line or skew I expect is an irrelevance. Forget the RPA cop-out and try and justify a linear extent of root protection. That's my view anyway.

[Calibre_Consultancy]

Thank you for your help both.

 

We are at very early stages at the moment. The client doesn't even have a draft design ready yet but as things go I would expect that they would be looking to incur on the vegetation.

 

Thanks again