Project: Minazi Low Cost Housing, Rwanda
Design team: Kubwimana Patrick, Mutuyimana Josue, Murindangabo Lambert (Year III, University of Rwanda, School of Architecture and the Built Environment.)
The site is located in the Minazi sector, Gakenke district, North province in Rwanda. It is located in a rural context, within proximity of several villages affected by landslides that occurred during the rainy season in April 2016 where some people lost their lives. At the moment, many families are still living in tents. They lost their houses, farmlands as most of them own plots in risk zones.
We chose to develop our settlement on a sloped portion of the site even though the community chose to live at a flat portion of the site in order to give them the prototype of managing the slope as Minazi is dominated by a sloping landscape. Around 80 percent of the land is more than 40 percent of slope.
We also focused on the country policy of zoning that involves land consolidation whereby the community lives closer to each other so that they can access the communal farming area. We utilised these farm lands as communal spaces and created other smaller common spaces for use by 4 families to increase socialisation amongst the community.
As we researched about the settlement, we got this quote:
“Human settlements are like living organisms. They must grow and they will change. But we can decide on the nature and that growth -on the quality and the character of it- and where it ought to go. We don’t have to scatter the building blocks of our civic life all over the countryside, destroying our towns and ruining farmlands” -James Howard Kunstler.
We found that a settlement is not just a set of houses but an organism that should have a specific character for the specific user. We decided to develop a concept which reflects African identity in a Rwandan settlement which will expand in clear and logical rhythm.
The fractal1 concept was chosen because in everything from braided hair styles, artefacts (e.g. Imigongo in Rwandan culture), to the design of housing settlements, the geometric structure known as fractals permeate African culture.
We considered the issue of Minazi which is landslide prone due to the slopping nature of the site and poor drainage of water since the region experienced heavy storms of rain. So the fractal system was used to develop drainage systems to scatter water in farming land and collecting water used from homes to farmland in form of net patterns whereby the velocity of water will be reduced.
Understanding concepts from the design
In simple terms, a fractal is a geometric composition that can be split into parts each of which is a reduced size copy of the whole, kind of like the Russian doll concept with the basic mathematical principle being self-similarity of forms. Examples of fractals in nature are: beehives, the tree structure (branches-veins-roots all are connected in the same ‘veiny’ manner.)
Applications of fractal systems in affordable housing:
Fractal systems of construction bring the advantage of replication of a similar form in a pattern, which gives an aesthetic appeal and because of the repetition of the singular construction element, economies of scale are possible because this allows the possibility of mass production of the element. It also saves time, and is easy to train the personnel developing/producing it, because once the underlying principle of construction is grasped, it simply has to be repeated over and over.
Fractal systems and structural strength:
A well-executed fractal system creates bonds within the system through the almost infinite interconnections, and so, within a small surface area, the elements creating the fractal system can spread their load over much larger surface area thereby distributing it amicably. Think of it like a bee-hive matrix of support. The numerous connections serve as a distributing system for any load expected on the structure, with the added advantage that the material providing the support is light.
Design for areas in landslide prone regions:
As is the case with many areas that are prone to natural calamities like earthquakes, floods or landslides, the design approach for the architecture takes on more of a mitigative than a preventative approach. In our Ugandan scenario, landslides commonly happen in the East around the areas surrounding the hills of Mt Elgon like Bududa.
Like at the Minazi region, the main reason why landslides occur in Uganda is because of the heavy rains that, coupled with the loose top-soil due to cracks in the earth’s surface as the aftermath of the volcanic forces from the earth’s crust presents a time-bomb waiting on the earth to cough a little. When that happens, the result is a landslide.
Traditionally, the Gishu builders in an attempt to control the destructive effects of landslides would level the land, and to reduce the difference in the slope, pile stones and make a solid foundation (in a fashion similar to a raft foundation). In addition, they prepared drainage channels around their courtyards to ease drainage of storm water. However, this usually is not enough to hold back the forces from the soil and from the force of the water flowing down after heavy rains. In a bid to protect the lives of citizens that had homes in Mbale at the slopes of Mt Elgon, the residents in those areas were relocated to areas in the low-lying areas.
Design for landslides therefore requires mitigative measures through intense drainage channels to allow the site to drain off fairly well, as well as providing a solid foundation on which the house can be lain, which is what the design team in this Minazi project did. They provided a retaining wall of stone, a material that can be easily acquired in the region for their foundations while using the courtyard spaces created by the negative spaces from the housing units as a netted drainage pattern to lead water off the site, with reduced speeds enabled by the terraces created.
However, another material could be brought into play to mitigate the forces from the lateral load brought about by the soil after a landslide. This material is concrete. The force from the sweeping action of the volume of soil that makes its way from the units at the upper slopes of the hill, will have reduced considerably due to the brilliant orientation of the units here in these young designers’ fractal system.
But, what would happen to the houses at the top that act as buffers by virtue of their location? In my opinion, the houses at the top -that face the first impact- could have that structural wall designed in a concave shape with concrete. Concrete is good in compression. If anything, the force from the soil will simply strengthen the concrete wall.
Special thanks to: Maria Sheeba Atukunda, Priscilla Namwanje, Waseka Allan, Akahiirwa Sandra Vanessa for their insights to this piece.