It’s never too late: Time for the Environment Agency to publish 2010 work on energy crops and flood mitigation

Woodland for waterBack in 2011 a review of the potential role of woodlands in improving water quality and alleviating flooding issues was published by Forest Research. It’s called Woodland for Water: Woodland measures for meeting Water Framework Directive objectives This deals with a very broad definition of woodlands and includes short rotation coppice (SRC) and short rotation forestry (SRF). It is very authoritative and includes 332 references. I was thrilled to learn that there was a real potential for perennial energy crops to help in flood control. Basically, energy crop plantations act as ‘green leaky dams’ holding water back and reducing its flow across the floodplain.

It’s not promoted as a silver bullet (there isn’t one) but is viewed as a definite part of the flood risk management toolkit. The report states:

“….the rapid growth and multi-stemmed nature of these crops makes them ideally suited to flood risk management.”

“……energy crops can offer additional advantages for water protection, flood risk management and climate change mitigation by enhancing pollutant uptake and sediment retention, more rapid establishment of vegetation roughness (especially for SRC) and increased carbon sequestration, as well as a more attractive and faster economic return for landowners.”

BUT it adds

“….there is no incentive to plant (energy) crops where they could benefit water most.”

I must admit that I really did see this as a breakthrough moment for SRC in the UK – dare I say a watershed! I believed that it was only a matter of time before this report permeated its way into further research, Government policy and support mechanisms for farmers.

Right from the word go Crops for Energy has plugged the report time and time again in our publications, in our blogs, in conference publications, in letters and emails, and articles and yet nothing has happened – well not for energy crops at least!

Why should this be? In the last 7 years the UK has been beset by some of the worst flooding events in history:

Month and Year Areas affected Number of properties flooded
June-July 2007 Hull, Doncaster, Sheffield, Tewkesbury 55,000
November 2012 Ulverston, Conwy, Denbighshire, Newcastle Upon Tyne, Darlington, Llanberis, Galashiels, Dumfries and Galloway, Cornwall, Devon, Somerset Levels, Gloucestershire, Midlands 8,000
Dec 2013-Feb 2014 Somerset Levels, Oxfordshire, Buckinghamshire, Leatherhead, Boston, Rhyl, Dorset, Hampshire, Kent, Dumfries and Galloway 10,900

Flood control has been at the top of the list of priorities for DEFRA and the Environment Agency. You’d think a measure that could potentially reduce the flow of water and provide greater warning time for people living in properties downstream would be a must – especially one that is relatively cheap, could have an almost immediate positive effect and produce renewable energy as well! But it’s not even on the radar.

By contrast the use of “native” woodlands for flood mitigation has made major steps forward. There have been pilot projects set up, mapping research looking at the most suitable areas to plant woodland for flood mitigation, detailed Forestry and Water Guidelines, and even a £2,000 uplift on the Woodland Creation Grant for farmers planting in floodplains. Don’t get me wrong I love trees and we certainly need more of them. However, planting native trees for flood mitigation seems like an odd choice in comparison to perennial energy crops. Here are my reasons:

Hydraulic roughness – holding back the flow of water is improved when you have roughness created by vegetation. This holds back soil which in turn reduces the flow rate of water. Mature SRC willows and miscanthus have much greater hydraulic roughness than woodland and achieve this in a fraction of the time. Native woodland is usually planted at a stocking rate of 2,250 per hectare and just when you start to see some real roughness (10-15 years after planting) the woodland is thinned. If you plant natives at a closer stocking rate (say 10,000 per hectare) you are likely to create scrubby woodland that is impossible to harvest and has no fringe benefits. By contrast energy crops are planted at much closer spacings and are really dense after 3-4 years. Even after they are harvested (to supply local energy projects or power stations) they grow back really quickly.

The table below shows the differences between the various options:

Vegetation option Woodland SRC Miscanthus
Time to maturity > 20 years 4-5 years 4-5 years
Stocking rate(plants per hectare) Typically 2,250Grant allows 10,000 on lower lying parts of the floodplain 15,000 13,000
Management Thinned after 15 years Cut every 3 years Cut every year
Hydraulic roughness(Manning’s n coefficients) 0.05-0.12 0.1-0.34 0.2
Potential of reducing flood risk in < 10 years Low Medium – High Medium -High
Subsidy payments for flood defence (arable land in lowlands) under previous Rural Development Programme £2,800 per hectare establishment grant,£2,000/ha one off additional contribution for flood mitigation, £300/ha per year for 15 years.Total subsidy: £9,300/ha 50% of establishment costs (~ £1,250/ha)Total subsidy: £1,250/ha 50% of establishment costs (~ £1,250/ha)Total subsidy: £1,250/ha


5 year old native woodland (top) has a vastly inferior hydraulic roughness to 5 year old crops of SRC (middle) and miscanthus (bottom)

5 year old native woodland (top) has a vastly inferior hydraulic roughness to 5 year old crops of SRC (middle) and miscanthus (bottom)

So, based on this we really should be pushing perennial energy crops for flood mitigation or at the very least be rolling out some trial projects. But we’re not. In the raft of initiatives that have come since the 2012 and 2013 floods the use of perennial energy crops isn’t even mentioned. The most obvious fit would be in the Environment Agency’s Working with Natural Processes to Reduce Flood Risk programme. However, in the R&D framework document there is no mention of perennial energy crops and only one mention of vegetation roughness in its 156 pages. Furthermore, in the accompanying data and evidence register that contains information on 547 projects there is not a single incidence in which perennial energy crops are mentioned.

As you can imagine this leaves us very frustrated and annoyed. We’re really hacked off with this that and we’ve made it our business to try and find out the reason for this oversight.

Turning back the clock a bit…
In January 2013 we saw an article in the Bristol Observer called “Team of experts tackle flooding” which mentioned that Bristol City Council and the Environment Agency had teamed up to try and reduce flash flooding incidents in South Bristol. I contacted the Flood Risk Manager at Bristol CC about the potential for a trial. In the end it was decided that it would make sense to involve the University of Bristol’s Department of Civil Engineering. In the autumn of 2013 two students embarked on dissertation work looking at the feasibility of planting energy crops for flood defence at various sites around the city. It is hoped that this project will be taken forward each year by new sets of students, initially looking at land owner engagement and hopefully leading on to the establishment and monitoring of field trials.

The work was important for a couple of reasons:

  • Firstly it has helped create links and has got people discussing energy crops as a potential solution (for instance Bristol CC have recently engaged the major consultancy group Arup to help move things forward).
  • Secondly, the students turned up an interesting reference to an abstract of a paper delivered at the European Geosciences Union meeting in 2010 called Energy crops on floodplains – flood risk or benefit?

On reading their dissertation titled Utilising Vegetation for Flood Mitigation and Biofuels, I immediately focussed on this reference and tracked it down. I was somewhat surprised to see that amongst the authors was a representative of the Environment Agency along with the lead authors from JBA Consulting. I contacted JBA and was flabbergasted to find out that back at this time they had been commissioned by the Environment Agency to do an investigation into the effect of energy crops on floodplain flows. The aim of this work was three fold:

  • To make sure that energy crop applications under the Energy Crops Scheme were not unnecessarily refused on a precautionary basis
  • To explore a range of energy crop plantation configurations on the floodplain and how these might influence 1 in 100 year flood water levels
  • To inform new guidance and practice regarding energy crops on floodplains and supplement EA guidelines entitled Flood Risk Management: Woodland, tree planting and flood risk.

A lengthy report and a briefing note were produced. They are cautious in their recommendations (as a result of the limitations of the model based on just two case study floodplains and the lack of other published information on roughness characteristics of energy crops) but broadly support this application of energy crops.

The briefing note says:

“In line with the long term objectives of the Catchment Flood Management Plans (CFMPs) these energy crop plantations could potentially have an important role to play in helping to manage smaller-scale flooding problems where the high cost of constructing hard defences cannot be justified. These plantations could also make a valuable contribution to tackling the increased risk of flooding associated with climate change”.

The report also calls for a more robust modelling exercise as well as laboratory and field studies. This work was completed in April 2010 a full fifteen months before the Woodland for Water report but was never published on the Environment Agency website. (A paper summarising the results of the work was delivered by JBA at the British Hydrological Society’s Third International Symposium Managing Consequences of a Changing Global Environment and is available here).

I spoke to several employees of the EA and it appears that the staff member involved moved positions at this time. As a result it seems that the work was left to fester at the bottom of someone else’s in tray.

Just think what might have happened if this work had been published at the time – Natural England may have been encouraged to make a similar £2,000/hectare uplift in floodplains available as part of the Energy Crops Scheme and improve the popularity of the scheme. The additional interest amongst farmers might have given rise to an ECS 3 and also encouraged DEFRA to fight for SRC to be retained on the list of greening measures under the new CAP.

Who knows, if some plantings had resulted in crucial flood risk areas we might even have seen some initial benefits during the terrible storms and flooding incidents in 2012 and 2013? Let’s say some well-placed energy crops plantations could have held back the water flow by an hour in one or more of the districts affected – just how many possessions might have been moved out of harm’s way? How much in term of insurance pay outs could have been prevented? And how much might the insurance premiums of home owners in floodplains have been protected? Unfortunately, we don’t know and we never will. And even if these imaginary energy crop plantations had a minimal effect we would have some pretty good hard data to use in order to refine the approach in the future. This is all very speculative but it has to be recognised that there can be consequences when important publicly funded research is not published. 

What’s done is done and we need to move on. Our view is that the following activities are required:

  • The Environment Agency needs to publish this report and briefing note on their website and share the information with Government departments (DEFRA, DCLG, DECC).
  • The planting energy crops on floodplains should be amongst the toolkit of measures being considered by the EA’s Working with Natural Processes to Reduce Flood Risk programme.
  • The ongoing mapping exercises being carried out by the Forestry Commission need to also include SRC and miscanthus. Priority should be given over to those areas where energy crops could have the biggest impact, e.g. areas that have a high degree of flood risk, high proportion of off gas properties and low forest cover.
  • A full evidence base review and cost/benefit analysis of SRC and miscanthus production and use should be undertaken that demonstrates the multifunctional environmental and socio-economic benefits.
  • Work is needed to identify what incentives are required in order to encourage farmers to plant perennial energy crops where they could have the largest multi-functional impact. This should enable the design of appropriate schemes/remuneration packages for growers with similar benefits to those promoting traditional woodland planting (e.g. uplifts for flood defence, carbon abatement etc.)
  • Basic research is required that looks at the application of existing and near market SRC varieties that are particularly suited to flood defence (e.g. flush early, senesce late, have leaves down to the ground and retain dead leaves over winter).

    One year growth of SRC willow variety Terra Nova. This variety has leaves right down to the bottom of its shoots and keeps it leaves late into December. Increased vegetation roughness and flood mitigation potential of coppiced trees could be selected for in breeding programmes.

    One year growth of the SRC willow variety Terra Nova. This variety has leaves right down to the bottom of its shoots and keeps it leaves late into December. Increased vegetation roughness and flood mitigation potential of coppiced trees could be selected in breeding programmes.

  • Networks of long term trials/demonstration plots need to be established. These would be used to test and monitor the effectiveness of perennial crops in a variety of multifunctional applications including:
    • Flood defence
    • Biofiltration and water quality improvement
    • Biosecurity barriers
    • Remediation of contaminated land
    • Agroforestry application

So come on Government Departments and Agencies and research organisations – let’s work together to make sure we can at last harness the excellent multifunctional potential of perennial energy crops.