This past weekend I did a consultancy of a property that illustrates the power of understanding how water moves through a property and the consequences of getting it wrong. What is interesting is that understanding these systems can save your clients thousands – and potentially millions – of dollars in lost real estate, infrastructure and, potentially, loss of life. If ecological design is going to be taken seriously, ecological designers need to address these problems in terms that people can understand: financial, life and infrastructure risks. If we do our jobs right, we will fix the planet as a bonus.
Before we get to the case study I need to explain a few concepts, specifically “The Formative System,” “Alluvial Fans” and “Water, Access, Structures”.
To understand water and how it interacts with a property we need to understand the formative system in which water flows through. The formative system is the elements in the greater bioregion that are “unchangeable” and significantly impact how water, wind, sediment, heat and cold interact with a property. Some of these unchangeables include:
- Climatic regions such as maritime, continental, tropics, sub tropics, arid etc.
- Climatic patterns: wind, rain, heat, cold
- Geology, hydro-geology and specific geological formations
- Long term climatic patterns of drought and wet/flood
- Location of property relative to the greater watershed
These unchangeables can provide an enormous amount of insight into how water interacts with a landscape and direct where things are placed to maximize productivity and minimize disaster and liabilities. Here is an example of a formative system that most of you will be able to relate to.
The formative system for Delta, BC:
- Maritime, Mediterranean climate
- 2/3 of the year in rain, salt laden wind, USDA zone 7 or 8, 1/3 of the year no rain.
- Located on a river delta, highly silt soils, high water table, earthquake prone
- Not prone to drought
- Located at the bottom of the water shed, high nutrient availability, prone to flood, prone to river channel migration, prone to salt water inundation due to tidal movement.
It is these forces that give this ecosystem its shape and should be crucial components in how you go about creating design. Any attempt to manipulate these forces will usually end up failing as these forces are formative and relentless. These elements can be used to inform how water will interact, which should inform how everything else should be placed.
Here is a definition of an alluvial fan.
Alluvial fans are high energy drainages that are subject to massive erosion and deposition. The power that they convey is proportional to the catchment area feeding into the apex of the fan. Below is a catchment analysis that Jesse Lemieux did of Cougar Creek. This analysis makes it pretty clear that homes should not be built on this high energy fan.
Where am I going with this? Well, with a proper understanding of natural processes and systems, it is possible to create designs that are not only beneficial to ecosystems, but can save lives, property and millions of dollars.
Disadvantages of Alluvial Fans
Advantages of Alluvial Fans
While we have focused on the disadvantages of alluvial fans they also have some advantages:
Cougar creek in Canmore is an example of a development a that was built on top of a formative system that is defined by an alluvial fan.
Alluvial fans like Cougar Creek are high energy environments that are fueled by enormous catchments (See Jesse’s Catchment Analysis below). Even with the large amount of engineering that went into the design of the channel, a 200 – 500 year rain event and three failed ice dams completely destroyed it and the homes around it. If development is allowed here again, the result will eventually be the same. The analysis that should be conducted should follow this order of operations:
- What is the formative system?
- How does water interact with that formative system in 100, 200 and 500 year events?
- Where is the historic fall out of sediment prior to development? In other words, what did the fan look like before we built houses on top of it? This will give us information of past rain events and potentially how likely they will return within 100, 200 or 500 years.
- Which homes or buildings are built on top of this fan?
- Which homes should be deconstructed to prevent further loss of infrastructure in future events?
Basically, once the size of the historic fan has been marked, it is safe to say that development should not be placed there.
Jesse’s Cougar Creek Catchment Analysis
Area X Depth = volume. 1 cubic meter = 1000L.
I hate to say it but I doubt trees and swales would have done much to prevent this from happening. Unfortunately subdivisions built on high energy environments, such as an alluvial fan, are subject to these kinds of events.
On a long enough time line, all mountains end up in the ocean.
But then, what do I know, I have never had the authority to sign off on civil works.
Design Methodology: Water, Access, Structures
One of the mantras that we use for property design is “water, access, structures”. What this means is you figure out where the water is coming from and going to and this informs where access (roads, paths) can safely and inexpensively go and from there you are only going to have a few locations to place structures (homes, food systems, barns). Water is always first for the following reasons.
Life depends on it, and without biological life on the planet, we can’t live here.
Water is detrimental to most forms of access and structures.
Water is relentless and will follow the path that it wants to. You can only force it to follow you for so long; it will always win.
This is a fantastic way of looking at design! However the formative system is extremely important to identify as it has a dramatic influence on how water interacts with the landscape.
Here are the same questions we asked above and how water may be affected by them.
Climatic regions such as maritime, continental, tropics, sub tropics, arid etc.
Does the rain or wind have salt in it? How will this affect vegetation? What are the temperatures like at various times of the year? Is spring melt going to occur when the ground is frozen? What seasons exist and how does this interplay into the functioning of the ecology, how water infiltrates, and how the system naturally harvests water.
Climatic patterns: wind, rain, heat cold
How does the rain come: thunderstorms, extreme downpours, low intensity rain over long durations? Are there consistent droughts yearly, or some longer cycle (years). How do heat and cold patterns affect vegetation, and how does this vegetation affect water infiltration. Are flash floods likely? Do long periods of dry impact fire risk?
Geology, hydro-geology and specific geological formations
Is the soil sandy, clay, or silty? Is there a high or low carbon content? Is the soil susceptible to erosion or mudslides? How does this affect infiltration, capacity to hold water? Are there Alluvial fans in your catchment? How high is the groundwater? Are there springs on the property? Are you on a flood plain? If yes, what is the return cycle?
Long-term climatic patterns of drought and wet/flood
Is there a 5 year wet and dry cycle? Is it longer or shorter? How will this impact how you manage the dry or wet periods?
Location of property relative to the greater watershed
Are you at the top or bottom of the watershed? Does the water that comes in have high or lower energy? Does it convey little or a lot of sediment? Does it convey other things like chemicals from industrial agriculture, septic effluent or other pollutants?
Once we identify and answer these questions, design decisions start to become a lot clearer. For example, don’t place buildings on alluvial fans and don’t build roads on top of springs or wet zones. What is really neat about following this methodology is that, when you combine it with the goals for the client, the design literally starts to design itself. I like to create a concept plan at a high level to identify areas of activity that make sense from a water perspective at this point. Once these areas are identified, then you can zoom in and do detailed design for each of the areas.
Read on to see how this applies to our case study!
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Great article. This is the kind of analysis that we need to integrate permaculture into the governance and civic composition of our future society.
Keep it Up!