Designing in the Face of Fire

Part one.

Feb 23, 2024

I will say before I go on, I am not competent to write a definitive piece on how to safely design for, fight and survive wildfire. I have no direct, personal experience of fighting either forest or wild fires. What I present here is what I have learned from others plus my own thinking on the subject. My intention is to promote awareness and preparation in advance of what is to come and hopefully generate some discussion and useful ideas.

Also, I write from the point of view of a relatively isolated, rural, forest dweller and that, on the surface, seems a most likely place for fires to occur, particularly in an overstocked plantation, largely unmanaged for a least the last fifty years. (you can find details in my previous pieces here on Substack, The Three Fates of Coed Y Brenin and Fire).

above: after the 2020 Afon Wen fire, about half a mile from our place. Fortunately the site had been clear-felled previous to the fire and because of the steep slope, the bulk of the debris had been removed, thus greatly reducing the fuel load. The steep slope meant the fire burnt rapidly uphill but fortunately, again, met a strong head wind at the summit and went out. It was started accidentally by careless use of an angle grinder at the bottom of the slope.

However, recent severe fires in various places, such as Haiti, Chile and of course the Fort McMurray but also fires in the UK1 have demonstrated that suburban and urban landscapes are increasingly involved in severe fires and it may be that we will soon see major, large scale fires affecting towns and cities here in the UK. Individual homes have in many ways become potential fire bombs due to the prevalence of petroleum based products in furnishings, wall and floor coverings, insulation, furniture, external wall claddings, window and door frames etc. It may be that long past disasters such as the Great Fire of London in 1666 will be repeated in our lifetimes.

I have been increasingly aware of the risk of wild fire for the last quarter century, as it seems to me that given the current inevitability of continuing global warming, it is similarly inevitable that we will all face fire at some point in our futures. With wildfire in mind I became a fire watcher, read books about it, followed news stories and paid attention to folk who have had direct experience. In particular, I was informed by the experiences of Bill Mollison2, whom I met in 1990 and David Holmgren3 in 1994.

I have been a weather watcher since the mid 1980s (which I will treat in more detail when I look at rainfall in Coed Y Brenin and forest hydrology) but in the last decade or so have also become a committed fire watcher. Here's a quote from John Vaillant's excellent book, Fire Weather (p335):

“For every 1 degree of warming, 15% more rain is required to cover increased evaporation.”

This simple statement deserves reading again. Its not so much the heat of Global Warming that leads to disaster, it is the increasing aridity of environments when that water lost through greater evaporation is not replaced by increased rainfall. This growing aridity is occurring in many countries throughout the world, hence the proliferation of the number, frequency and intensity of wildfires.

above: simple, cheap device measures inside and outside temperatures plus humidity. Oh yes, its a clock too…

Aridity is the single most notable precursor to catastrophic fire, hence as a fire watcher a vital piece of equipment is a humidity meter. These are very cheap and usually come with a thermometer, another essential for a fire watcher. My monitor measures humidity plus inside and outside temperature and cost well under £20. A third essential is an awareness of wind speed. While harder (or rather, more expensive) to measure accurately, useful estimates can be gleaned from the environment- the Beaufort Wind Speed system relates wind speed in miles per hour to environmental effects, such as the movement of twigs, leaves, smoke and the like. Good observation round your site can increase your appreciation of wind speed and you can make it easier to observe the effects by interrupting the flow4.

Our little Rutland wind turbine5 provides such an interruption and indicates direction and a rough gauge of speed; you get used to the varying whine as it spins up and the remarkable shrieks it produces in strong gales (the blades have only broken once, in our first hurricane force 12 storm). Also, flying Y Ddraig Goch (the Red Dragon of Cymru) or other suitable flags and banners gives a good idea as well of wind speed and direction, as making a cultural statement.

above: flapping flags indicate wind speed and direction and can make a point.

However, local topography is critical and fires can burn up slopes without the aid of wind.

“Where a slope is going upwards at a 10% gradient that would double the speed of the fire, if its 20% it would quadruple the speed of the fire...that's because it's pre-heating the fuel above it. So if a fire is going up a mountain it will go very fast.”

according to Rob Gazzard, technical advisor to the Forestry Commission, from the BBC news website. The fire pre-heats material (fuel) on the slope above and can move with frightening speed, the steeper the slope, the faster and hotter the fire.

The critical numbers to be aware of as a firewatcher are 30-30-30, meaning, when the temperature is at or above 30 degrees C, the humidity at or below 30% and wind speed around or above 30 mph which translates as Beaufort scale 6, and given as:

“Large branches in motion; whistling heard in telegraph wires; umbrellas used with difficulty".

While fires may occur outside these figures, the convergence of these three measurements indicates when the fire risk becomes very high.

Another measurement you can make is rainfall. Again, a simple rain gauge is cheap and you learn a lot from taking a reading every day. With well over ten years of data gathered here at Penrhos, I can see clearly that although the total annual rainfall has remained within the same (very) broad range (from 1.8 metres to 2.4 metres) the occurrence has shifted quite dramatically, as predicted by climatologists studying global warming, with a tendency towards wetter autumns and winters and much drier springs and early summers, leading to lower humidity in April though to June, hence the increased fire risk.

above: simple rain gauge makes monitoring rainfall easy and fun. Get a youngster involved if you have one spare.

Lastly, the aridity of soil surface debris is also critical, that is, leaf litter, conifer needles under trees, mulch in gardens, wood chip on paths and “feg” (dead grasses) in fields etc. as this is usually where a fire will start. Though harder to measure without specific equipment, we can get a good indication by having a good feel in it; if dust arises, well, its pretty dry...

So now to fire and what we can do about it. I'll make a few basic points to begin.

1. Some fires are impossible to fight. In such situations, attempting to defend your own property is both futile and potentially fatal. All you can do is run away and wait somewhere safe until it goes out. With that in mind there are still things that you can do to prepare for your escape. These might include a flight bag with important documents or items already in it, or just having a bag ready and knowing beforehand where the things you really want to save are. A development of this is to install a fire-proof stash-place somewhere for larger items- probably underground.

2. Depending upon wind speed, temperature and aridity, any and all vegetation will burn at some point, hence there is no such thing as a fire-proof plant. However, some species burn less easily than others and I'll look at a provisional list, gleaned form books and the interweb, in part two.

3. Fire is capricious, fickle and highly unpredictable. It is informative to look at and zoom in on drone footage of fire sites and even more informative to be able to go and look yourself. It is not unusual to find areas that appear to be completely untouched yet neighbouring or surrounding properties have been burnt to the ground. Chance will take a big role in any fire event but we can influence chance with good design and through our own actions in preparing for and fighting a fire.

4. A wild fire on the ground moving through dry grasses in a field or low vegetation in a woodland is relatively cool (relatively! Its still hot) due to the limited fuel available to it- it burns fast and goes out quickly. The smoke will tend to be white or grey and from a distance you might not see any flames. If the smoke turns black and you can see flames rising up in it, then the fire has found larger quantities of fuel and/or got into the tree canopy where there is loads of material to consume. It is now probably impossible to put out from the ground. Be ready to run away if it is coming in your direction.

Turning to design and preparation, its useful to think in terms of “no loss” techniques or modifications- that is, things we can do that are useful anyway, whether there is a fire or not. The most valuable here is probably good water management. Having access to an adequate water supply is obviously an essential in any permaculture design as well as being critical in fighting fires and, as mentioned above, with increasing aridity, more and more demand will be put upon conventional water supplies.

For a rural property, if at all possible, it is extremely useful to arrange your water supply as a "flow-through" system. The most basic of flow-through systems is just a hosepipe in a stream or other water source, above your property, that runs into a tank by your dwelling that then overflows and is piped back into the stream. It is then very easy to just cut the pipe at convenient places and stick another tank, bath or pond in and so on, so water storages are built up in series, each one overflowing into the next.

Note that there are no float valves involved so the water flow is continuous, as in “flow-through”, which also greatly reduces the chance of the system freezing in winter. Its worth pointing out that a flow-through system does not require a huge flow of water; our feed pipe measures 20mm internal diameter and runs at just a dribble during very dry spells and though the levels in the tanks will fall during the day the dribble is sufficient to refill them overnight, so far at least...

Here at Penrhos we have had over thirty years to design and refine a comprehensive flow-through water supply, in part with fire fighting in mind. The central part of the system is a series of interconnected tanks (fruit juice containers at approximately 1800litres), each one overflowing into the next, built up gradually as funds became available. The first tank in the series supplies the household water, the second tank feeds through to livestock and a third provides water to the garden areas. In addition, each tank feeds to individual standpipes, positioned to the west, north and south of the dwelling. Each standpipe has an attached hosepipe with a spray nozzle, meaning the house and surrounding vegetation can be dampened down before a fire front arrives and/or be used to put out spot fires.

above: various tanks in the Penrhos flow-through system, each one feeding into the next.

A fourth tank is kept as a reserve, specifically for fire fighting or use in extreme drought conditions when the primary tanks may run dry. There are several other legacy tanks in the system as further reserves and the overflow from the tanks goes on to service other areas further down slope.

Its an advantage to have water storage near to the dwelling, so as part of the flow-through system here we have various old baths and tanks which as well as providing opportunities for irrigation of growing areas, can also be used to damp down vegetation in the event of a fire and putting out spot fires (more on spot fires in part two). Be very aware though that water pipes on the surface or running through vegetation are themselves susceptible to fire.

As well as having water storage near to the dwelling, David Holmgren also mentions having simple methods of blocking downpipes so roof gutters can be filled with water in advance of the fire. Some energy from the fire then has to be diverted to evaporate this water.

In terms of permaculture design, fire can be considered when we examine zoning. Simply put, zoning identifies the wild, free and uncontrolled energies, materials and beings that flow through your site and would include things like wild animals, wind, sun, people etc. as well as fire. Here you would look at which direction the fire is likely to come from and what you might put in the way to slow it down or steer it. The direction will usually be that of your prevailing wind, so in the UK will tend to be from the west/south west for most of the year but local conditions will modify this6. Here at Penrhos, for example, in our little hanging valley with ridges to east and west, wind tends to be funnelled round to come up from the south or down from the north. Also, as I said before, fire is capricious, changeable, unpredictable and given sufficient fuel, can generate its own wind.

Wetlands and bogs are less susceptible to fire and can act as fire breaks. They're also potentially productive growing areas as the plants have access to water throughout the year. It is possible to create wetlands and bogs and the causeway system we developed here at Penrhos can be adapted to form part of fire control design as well as providing additional water storage and growing space.

unfortunately, very full, stacked plant systems with climbers bridging the gap between ground and trees, when dry, present a high fire risk. Similarly with wooden trellis cladding buildings with vegetation. When its hot and dry enough, these provide ladders for fire to climb up into the tree canopy where there is lots of fuel or into our roofs via the eaves. So leave spaces between growing areas and buildings, high prune trees that are near buildings to at least two metres and avoid the use of mulch or wood chip close to the house.

Its also important to consider which part of your property is most susceptible to fire. Here at Penrhos, we clad our kitchen with cedar boards from the forest around us. Cedar is a wonderfully stable, rot and bug resistant material that turns a lovely silver grey with age and blends perfectly with the stone work. However, it is extremely flammable. if I held a lit match to the lower corner of a bottom board It would catch fire before the match went out and the whole wall would be alight in a matter of minutes...gulp!

The main danger here is flammable material being left or allowed to grow against such a wall or wind blown, burning embers lodging in the cracks between the boards. The former is simply a question of being careful and tidy, the latter depends upon your wariness and watchful patrolling during a fire event plus the readily available equipment to put out small, spot fires, which can be as simple as a watering can.

Its also a situation where a series of small, interconnected sprinklers can make a significant difference. Either permanently attached along the top of the wall and connected to the gravity fed through-flow system or moveable ones that could be popped up on the roof in a hurry and fed through a pump. In Alberta, moveable, connected sprinklers with portable petrol water pumps are used to great effect, given a suitable water source (stream, pond, tank etc.) to damp down flammable structures or vegetation in the path of an incoming fire.

As I write this my rainfall record informs me that this February is on track to be one of the wettest I've recorded and we've still got a few days to go, so wildfire is probably the last thing on anyone's mind locally! However, things can change very quickly these days and it will be interesting (in the Chinese sense) to watch how things go as we move into spring and early summer.

Thanks for reading. In part two, which may not follow immediately, I'll look in some detail at the work of folk who are highly experienced and competent in preparing and esigning for wildfire, including Joan Webster7 and David Holmgren. I'll also present a provisional list of more fire tolerant plants and a simple method for finding out for yourself which plants burn best. Till then, take care and keep an eye on your humidity monitors- hwyl! Chris.

E.S.P. Adapt

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