Living with Fire – Part 1: Basic Fire Science, Personal Responsibility And Home Site Selection
For those of us that inhabit the urban-wildland edge, fire is a primary design consideration for developing and inhabiting regenerative landscapes. It is inevitable that, at some point, fire will touch the landscape where we live. There is only so much we can control when a fire does come. It’s the design, planning and preparation that precedes the fire that will largely determine a home’s survivability. As with most things, last minute preparations before the flames come are bound to be incomplete at best, and ineffective or dangerous at worst.
This article explores the ideas and concepts of Regenerative Firescaping for the high fire danger urban-wildland edges throughout California. While written from our perspective living on California’s Central Coast, the principles and strategies presented here are applicable across many different fire climates.
Regenerative Firescaping: A New Fire Paradigm
So often the regulations that govern mainstream firescaping are interpreted in a way that pits human settlement against nature in an endless cycle of noisy weed wacking, brush removal, chipping and burning that is a HUGE drain on both private and public time, energy and financial resources. What if we could step off this hamster wheel by harmonizing with natural vegetation patterns and employing intelligent design to actually invite fire’s renewal energy into our landscapes in a way that reduces risk to people, property and ecology?
We shall endeavor to do just that. Let’s begin with identifying the broad, overarching patterns that serve to anchor the Regenerative Firescaping paradigm as we move forward.
Firstly, fire WILL happen – and need to happen. Many ecosystems, particularly prairie, savanna, chaparral and coniferous forests, have evolved with fire as an essential contributor to habitat vitality and renewal. Fires clear out dead organic material that has accumulated, preventing organisms within the soil from accessing nutrients, animals from accessing the soil, and plants from receiving the light or oxygen to germinate. The seeds from many plants in fire-affected environments actually require the heat from fire to germinate. Wildfire suppression not only eliminates these species, but also the animals that depend upon them.
We can choose one of three ways to engage with fire; 1) to engage in year-round mowing, cutting, chipping, and burning to maintain a “defensible perimeter” (more on that later), 2) to do nothing and assume the fire department will protect our property (a big gamble), or 3) to accept, plan for and harmonize with it as one of the natural energetic cycles of the landscape in which we’ve chosen to live.
The first approach, to fight or suppress fire, works great. Until it doesn’t. It also costs a LOT of money, time and human energy. This is the expensive approach. The second approach is to abdicate personal responsibility and expect the fire department to protect one’s personal property. While fire departments do an amazing job with limited resources doing direct structure protection during thousands of fires each year in California alone, they cannot be everywhere at once, and their safety comes before protecting a home. The second approach is the lazy approach.
The third approach puts the onus of responsibility firmly on the individual homeowner and local communities to design, plan and prepare for fire’s inevitable visit. This is where the greatest potential for reducing fire danger and damage lies, while simultaneously creating more beautiful and enjoyable places to live. We will spend the remainder of this article coming from this perspective (plenty has already been written detailing the faults of the first two approaches already).
Once we’ve accepted that fire WILL happen, we have to ask the following question: Of all the factors that influence my family’s and my home’s chances of surviving the next fire, which ones can I control and which can I not?
Let’s start with what we can’t control/influence because that’s often easier.
Fire Risks Beyond Individual Control/Influence
- The weather – Santa Ana winds blowing? 90 degrees and 3% humidity? Nothing to be done about that.
- Other people – We always endeavor to work with our neighbors and local community, especially anyone that we share property lines with, but ultimately, we can control only ourselves, our decisions and our actions.
- Topography – If a home is already built, we can’t change the surrounding topography to reduce fire danger. If we are siting a home, we can choose where it sits amidst the topography to lessen the fire danger.
- Public utilities – Water and electricity service will often be suspended during a fire. If we are on the grid we need to plan for this as a likely scenario.
- Fire outputs – Heat and smoke will be present, and their presence must be planned for ahead of time. Potential consumption of available oxygen in immediate air mass following a high-intensity blow-over may also occur for a short period of time – this needs to be considered if forced to shelter in place.
- Timing of the fire – Murphy always plays his hand. We may not be present or capable of enacting fire protocols. What redundancies do we have?
Fire Risks Within Individual Control/Influence
- Evacuation Planning – Pre-planned routes, rally points, communication methods and places to stay. Pre-packed Go-Bags. Everything should be documented, with printed copies in each vehicle and each family member’s Go-bag. Rehearse regularly.
- Firescaping – Surrounding vegetative fuel load. We can prune to reduce fire ladders and fuel loads, select plants and arrange them for fire resistance. We can create buffer zones using berms, swales, pools, ponds, water tanks and vegetative elements.
- Access – Ample road width, turnarounds, elimination of low-hanging branches and/or tree tunnels. Secondary entrance and exit.
- Built Structures – Fire resistant design features. Fire resistant or fire-proof materials. Indoor and outdoor fire sprinklers. Floodable gutters. Lots more.
- Maintenance – Cleaning gutters of leaves and twigs, removing overhanging branches, sweeping up leaf litter/detritus piled against house. Interaction with landscape immediately surrounding home.
- Awareness – Paying more attention to news reports when fire danger is high. Reviewing do’s and don’ts with family. Subscribing to text alert systems.
Basic Fire Science
Looking at what we can control is empowering. There is a lot an individual homeowner can do to increase her home’s survivability during a wildfire. Before we dive into all those nuts and bolts, it pays for us to take some time to understand fire – what it is, what it needs and what strengthens vs. weakens it.
The Fire Triangle contains the three things needed to sustain fire – Fuel, Oxygen, and Heat. Take away an adequate supply of any one of the three, and the fire will extinguish. Knowing these three essential components to fire aids us in designing fire resistant homes and landscapes where heat or fuel cannot build up to substantial levels to combust (oxygen is omnipresent – this falls into the “Can’t Control It” category).
Another helpful graphic is the Wildfire Cube – essentially, by introducing high velocity winds with heat and low-humidity conditions, the chances a fire will escape “control” and cause massive damage increase exponentially. When conditions like this occur, our fire awareness should increase accordingly.
Fire danger increases as the atmospheric conditions trend towards becoming an “unstable air mass” – especially when fuels are dry (<35%). Things to look out for that fall in the “unstable air mass” category include shearing winds, ground whirlwinds (dust devils), scattered cumulus clouds, and shifting winds.
Knowing the essential ingredients for fire, and the special sauce that creates wildfires, we can now look at the landscape with an eye to increasing fire survivability simply based on where we choose to site our homes.
Topography And Fire Risk
An understanding of how topography (the arrangement of the natural and artificial physical features of an area) influences the speed and direction that fire takes in a landscape will help us to make informed decisions about where to best site homes, structures, and other elements in order to minimize their exposure to fire and provide residents with the most time to take proper measures.
The most important factor in topography as it relates to wildfire is slope. Unlike humans, fires travel uphill much faster than downhill – and the steeper the slope, the faster the fire travels. For every 10-degree increase in angle of upslope, the fire speed and intensity doubles. So, if a fire is moving at 5mph at dead level, it will move:
- 10 mph at 10 degrees slope
- 20 mph at 20 degrees slope
- 40 mph at 30 degrees slope.
This is primarily due to two factors: winds typically flow upslope, and increase as slope increases, blowing the fire more quickly that direction, and the fire is able to preheat the fuel further up the hill because the smoke and heat are rising.
Armed with this knowledge, it becomes clear that, in fire-prone areas, houses should, if at all possible, be located as in downslope and midslope areas instead of on ridgetops (but what about those views!). Few houses located on sharp ridges or in hill saddles that have diverging ridgelines creating a wind tunnel effect survive and out of control wildfire.
A similar wind tunneling effect is created by planting tree species of trees that are especially flammable alongside driveways in rows, creating a blow torch aimed directly at the house.
To reduce the susceptibility of fire moving uphill towards a house, radiant heat barriers (stone walls, patios, etc, discussed in more detail later) should be placed on the downslope side of the house to provide a shield from upslope convective and radiant heat. Houses should never be on stilts in fire-prone areas, as this makes them even more susceptible to embers and convective/radiant heat gain.
The safest house sites are those that have some or all of the following: consistent moisture, surrounding radiant heat shields and inflammable surfaces/structures, minimized fire sectors, and relatively low winds. These include:
- Damp valley mouths
- Well tended built up areas
- Farms with flood-flow or keyline irrigation fitted areas
- Peninsulas in dams and lakes
- Any plateau site where design and maintenance criteria are rigorously applied
Intimately linked to a home’s siting within the landscape is the ease with which it can be accessed (and evacuated from) by fire fighting vehicles. If we want the chance to receive any help from our local fire department during a fire we need to at least ensure that access to the property provides a safe entrance and exit for fire fighting vehicles. Things we can do to ensure access include:
- Maintain ample road/driveway width for large vehicles.
- Gates all similarly sized and able to be opened manually if needed.
- Keep overhanging branches or vegetation clear of roadway.
- Provide a turnaround or ample space to maneuver a large fire truck and quickly exit the property.
So we’ve selected our homesite with fire survivability in mind and planned good access for ourselves and fire fighting vehicles. How do we begin to create a regenerative firescape around the house site?
We’ll begin by looking at our zones and sectors in Part 2: Regenerative Firescaping – Protecting Your Home With Good Design.