Sunday, January 22, 2012
Preventing Floods in Your Garden
A long time ago I wrote to the Straits Times Forum grumbling about (irresponsible/deceptive) subcontractors of property developers who leave all manner of building waste, discarded food containers, wires, and so on buried in the garden plot in landed homes. Furthermore, the garden soil would be low quality clay with a thin layer of top soil covering it. Last year, my dad bought a terraced house along Corporation Walk, and I took charge of the garden. That was when I discovered, first-hand, these shady practices. That is not the point, but it paints the backdrop for this post on small-scale flood prevention.
Clay soil is horrid for planting, digging and draining water. My garden flooded horridly when I first moved in. I did a bit of clay removal last year, which improved the situation, but there was still flooding, albeit acceptable. Today, inspired by the potentially visionary point made by Minister for MEWR Vivian Balakrishnan that a prolonged drought would be more worrying to him than flash floods, I have decided to exercise my mechanical engineering muscle for the first time in real life (fluid mechanics, in particular; I transitioned to being something of an engineer of data-driven decision support systems from my third year as an undergraduate, but still got my degree in mechanical engineering).
Over time, I noticed that one area of the garden drained well, while another was dismally horrid, ponding (*snigger* *snigger*) with even low levels of rainfall. So I decided to channel some of the water from the former area to the latter. Now, a pipe would clog, and I didn't have the material. As a result, I settled for a sand channel. Sand is rather porous and a channel of sand would behave like a pipe. Now, fluid flow through a porous material is governed by Darcy's Law, which basically says that the flow rate is proportional to the gradient of the channel. So I dug a channel with a small gradient, and filled it with sand and prunings (just because), then covering it with some soil.
Long story short, when it rained moderately to slightly heavily just a while back, there was no more flooding. Now, with a little more civil engineering expertise (and a hundred million dollars), I'm sure we can get flooding under control in the city area. All it takes is a suitable application of engineering principles.