Attempts to mainstream nature-based solutions (NbS) will not be successful unless we get the planning right. Interventions for water-related problems are often put in highly inefficient locations when placed without any form of modelling, but full-blown hydrological modelling is too expensive. New, pragmatic approaches may prove to be our best answer.
There is currently a lot of talk about natural capital, nature-based solutions and ecosystem service – or whatever other buzzwords you wish to use. This concept of enhancing nature to solve problems can be very powerful, but only when done well. Unfortunately, this is not always the case.
Recent research by the Centre for Ecology and Hydrology suggests that around 50% of nature-based solutions (NbS) to water problems deliver no benefit at all. This means that millions are being spent planting lovely woodlands, for instance, but achieving no reductions in flooding or river pollution. I believe that this is because the interventions are being put in the wrong places.
It is vital to consider the landscape as a connected system when considering water-related problems such as flooding, drought, diffuse pollution or erosion. This is because the NbS to reduce these problems will often be needed far from where the problems are being felt. For instance, holding rainwater in upland areas can reduce flooding in lowland towns. Currently, there are three main methods of deciding where to create such NbS, all of which have problems.
The simplest is just to create NbS wherever the opportunities arise. This involves no modelling at all to identify good places from bad, and relies on the concept of ‘every little helps’. The problem with this is that outcomes are largely left to chance. Outcomes can vary from being a great success, through simply being a waste of money, to actually making matters worse. Planting trees on a flood plain may seem like a good idea, but can easily exacerbate flooding unless it's exactly right (which usually requires modelling).
The most common way of deciding where to place NbS is through mapping various characteristics of the landscape, such as soil type and topography. This geographic information system (GIS) analysis is great when benefits accrue at the interventions, such as a tree sequestering carbon, but is not effective when considering water. This is because GIS cannot understand flows or how different parts of the landscape interact. For instance, a steep slope with clay soils and no vegetation would seem ideal for planting trees to stop flood waters reaching the river. However, this would have no effect on flooding if a fen between the slope and river already captures all that water. GIS could not understand this and so would recommend planting trees on the slope regardless.
It is these sorts of interactions that the third option, hydrology, can understand. Unfortunately, hydrology and hydraulic modelling cannot suggest what to do where, but only consider the benefits of various given scenarios. This means GIS is usually used to identify where to do things, the benefits of which are then calculated by hydrology. Which brings us back to the problems of GIS modelling! In addition, full hydrological modelling is resource intensive, time consuming and expensive. It does give excellent results in terms of water flows and timings, but it can become unstable for catchments larger than about 20sqkm.
So, what is the answer to this rather hoary problem? I genuinely believe that Viridian’s HydroloGIS model solves all these problems at affordable cost – but I realise I am highly biased! Otherwise, we probably need a pragmatic mix of solutions. There will be times when highly detailed quantification of benefits will be warranted and others when simple GIS analysis will be adequate. The important thing is to consider what needs to be achieved, what evidence funders or purchasers require to release funds, and how best to involve stakeholders. This will guide us to the right tools for the job.
Without proper planning, NbS will often be created in the wrong places. The resulting lack of noticeable improvements in water-related problems will damage confidence in the entire concept of NbS and waste the money invested in these projects. Conversely, NbS will become prohibitively expensive if every project has to undertake detailed hydrological modelling to access funding. There are technological ways to navigate around these obstacles (yes, OK, that’s us again), but otherwise we need to work together to agree practical compromises. This is possible but needs a change in attitude from ‘business as usual’.
One final note: participatory design of NbS is essential. Some recent projects have shown how badly wrong things can go if stakeholders are ignored. Local engagement will both improve outcomes and guarantee longevity of NbS features: do not underestimate its importance!
Angus Middleton is a director of Viridian Logic, a company specialising in natural capital mapping and the high-tech design of NbS. Please see www.viridianlogic.com for more details or contact Angus directly ([email protected]).
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Please note: the views expressed in this blog are those of the individual contributing member, and are not necessarily representative of the views of IEMA or any professional institutions with which IEMA is associated
Posted on 28th October 2020
Written by Angus Middleton
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