Wednesday, May 24, 2006

On flash floods

There are many types of floods, but offhand, I can think only 3 of them: still flood, flash flood, and lahar. The first is what you see in low-lying areas (like Espana ave. in Manila); the second are those fast, cascading strong waters on rivers and canals; the third is sand + water (various mixtures, could be up to 80% of sand, only 20% water), prominent on areas that experience volcanic eruption like Mt. Pinatubo.

Mt. Pinatubo's sand deposit has hardened already, so we do not see lahar flows anymore in central luzon during the rainy season. Still flood could pester us because they occur on areas where there is often high population density, so the people can hardly move and small vehicles cannot pass through them. But still flood don't bring down with them your house or your car; it's just that with heavy downpour, the drainage cannot expurgate the rain water fast enough onto the canals, so there is temporary "lake" that is being created.

What people cringe about are flash floods. You see them on tv -- strong waters cascading on rivers and bringing down with them logs and plants, houses and small structures, farm animals, even people and vehicles. As strong waters rampage down, they also redraw river banks as soft soil on river banks fall down, so the river becomes wider.

In my treehouse in the farm, whenever I get trapped there by strong rains, I just watch a nearby creek suddenly turn into a wild river. I see the flood water rising inch by inch, minutes by minutes. Occassionally, we (along with our farm caretaker) could hear some loud "bangs" from there -- they turn out to be logs and/or uprooted roots of trees being transported down by the strong waters, and when they hit some big solid rocks, that's the loud bang or noise created. Since we watch on the 2nd floor, our view of the cascading river is quite good.

And since our farm is somewhere midland, I can only imagine the damage to crops, even houses, in the lowlands, before the flash flood would exit to and be silenced by a bigger body of water, the sea.

About half to one hour after the strong downpour has stopped, the wild river goes back to an ordinary creek. The muddy and wavy waters return to colorless water. Yeah, the flash floods have wiped out most of the impurities in the riverbeds and riverbanks. The crawling vines, the dark green algae, the decaying fallen leaves, and so on. And then you realize that flash floods have some positive results after all. And those huts and weak houses that the flash floods have knocked down is nature's way of culling the weak and non-durable. Also nature's way of saying that "riverbanks are for plants and water, not for houses". Nature makes this message clearer than "government warnings".

So, if typhoons' strong winds wipe off even temporarily the heavy air pollution deposit in urban areas, flash floods also wipe off even temporarily the obstructions and impurities in riverbeds and riverbanks. And if you gather big stones for whatever construction needs -- like our various stone terraces construction in hilly and sloping parts of the farm -- the flash floods expose the big stones as they have scraped off the small stones and sand. So, gathering the big stones is easier.

But overall, flash floods are more harmful than beneficial. That is why rainwaters should seep in the soil as much as possible so that flash floods will be minimized. From my experience, building lots of stone terraces on sloping lands really help a lot in controlling and minimizing flash floods. You put lots of organic matter (dried and fallen leaves, plants, tree branches, etc.) as filling materials, you cover them with soil. When strong rains fall, the terraced soil act like huge sponges gulping in as much water as they can, and release water down as little as possible. And the growth of plants and trees on those terraced soil are also fantastic. They have lots of organic matter and trapped water deposit in their roots.

Tuesday, May 23, 2006

On rains

It's cloudy and the sky's a bit dark this afternoon as I squat here in my sister's office somewhere in the middle of a 50+ storey building in makati. I pondered, why not write something about rains? It's late May anyway, and the only government agency of hope (Pag-asa :-)) says it's officially rainy season this part of the month.

Earlier, I have thought that when typhoon Caloy 2 weeks ago dumped tons and drums of rains from Mindanao up to the Visayas, Bicol and southern Tagalog regions, 'twas the start of rainy season already. I was wrong. Of course it was bad that Caloy killed many Pinoys in the Visayas and Bicol, but Caloy also drenched the parched earths of nearby provinces and regions within the perimeter distance of its wings. These included the central and western visayas, island provinces of southern tagalog, and central and northern luzon. Yeah, if you're a typhoon, you can kill some people, but you also give life and respite from heat to many other people, animals and crops.

What I like about rains and typhoons aside from the obvious benefits of drenching and irrigating parched plants, crops and trees, is that rains and strong winds wipe off even temporarily, the thick smog and smoke of vehicle, industrial and household pollution, over the skies of congested cities. That's why it's nice to "smell" the air of urban manila immediately after a strong typhoon.

Strong rains may cause flooding in low-lying areas, other areas where drainage was clogged by garbage, sand, stones, other obstructions. But strong rains also help in unclogging canals, drainage, of those obstructions, wipe out stagnant and nostril-assaulting smell of near-dead canals.

On the part of motorists and drivers, the rains are some sort of an equalizer. Hot-tempered heads cool down; fast-blastin' cars are fewer because almost everybody is careful and slowing down. Well, for one, when the streets are flooded, you don't know where the large potholes are. But someone told you (that's me, most likely, hehe) that government took away at least P15 out of around P41 per liter of premium gasoline that you just paid at the gas station, and you wonder why there are still many potholes in the roads. The tax money went down the drainage? Hmmm....

Until about less than a decade ago, when May comes, the rains almost always come, with or without a typhoon. Nowadays, the rains would come early only when there are typhoons. That is, no typhoons, no early rains. Last year, one of the "driest" years I can remember, there wasn't much rain. Just some of the explicit proof of "global warming" perhaps that many people and environmentalist talk about.

Btway, the same group of environmentalists who complain of ground water over-extraction and global warming also oppose the construction of many golf courses. They say that during summer, those greeneries are a-gulping drums upon drums of water everyday. Yeah right, but precisely that those greeneries are gulping drums upon drums of water that they are useful during the rainy season. If those golf courses are basketball stadiums or tennis covered courts or malls and subdivisions, they'll be cemented. The rains fall on hard pavement, go straight to the drainage, onto a canal, onto a river or ocean. See, no replenishment of ground water extracted. Since those greeneries are not cemented, the grasses and trees are like thirsty monsters that gulp in as much water as they can, a big portion of which has filtered onto the ground water table.

Makes me think further, that people should minimize cementing their surroundings, especially around their houses. Yeah it can be muddy when it rains, but there's also less street flooding as the open space gulp in a big portion of the rainwater. Also, if you planted trees near your house, chances are that when those trees have grown big, they're like incredible hulk cracking and destroying those cemented walkways as their roots grow bigger and higher.

And finally, the romantic side of the rains. Our wedding give aways last December was a CD that contains 10 of our favorite songs, with a paragraph discussion of each song why we chose them. Yeah, you guess it, many of those 10 chosen songs are from my favorite rock bands -- Bruce Springsteen, Rod Stewart, Beatles, hehehe. I included one Pinoy song -- "Tuwing umuulan at kapiling ka" (originally by Basil Valdez, our version sung by Eraserheads band). Imagine you're in my no-walls treehouse, on the 2nd floor, atop a big tree, the rains are pouring hard and the winds are cold, and you're hugging your gf/bf or spouse as you watch the rains and the waving leaves of trees around you, what a feeling, right? Awwww! hehehe.