One flood. Three days -> One canyon.

We often get glimpses into the overwhelming power of nature. One such was in June-July 2002 in Texas: Fearing the worst during torrential rains, the waters of Canyon Lake (a reservoir on the Guadalupe River) were diverted into an emergency spillway. The consequential flood event, with a flow rate of over 1450 cubic metres per second and duration of six weeks, destroyed a bridge and trees, and carved a 2.2 km long, 7 m (average) deep canyon into the limestone bedrock. This new Canyon Lake Gorge is highlighted by Michael Lamb (Caltech) and Mark Fonstad (Texas State University) in their paper published in Nature Geosciences on the ‘Rapid formation of a modern bedrock canyon by a single flood event’.

Deep river canyons are considered to have formed gradually over the millions of years as a result of moderate and recurring flow of water. Megaflood events too results in similar canyons and channels, except that these are formed more rapidly, as in the case of the Canyon Lake Gorge. In this event, it is undeniably known that the erosion happened during the flood and the more destructive episode happened over a time span of just three days.

Using pre and post data and techniques (aerial photographs/images, models, flood measurements) Lamb and Fonstad analysed the formation of the canyon, identified the characteristics, and reconstructed the hydraulics of the flood. The important findings are:

- The rate of gorge erosion/formation was rapid, limited only by the amount of sediments carried by the floods. About 460,000 cubic metres of materials were dislodged, almost half of which were rocks. Even boulders with a size of 1m were plucked and moved downstream.

- The very creation of the canyon was dependent on the nature/characteristics of the bedrock. For instance, the aforementioned plucking of the 1m limestone boulders was facilitated by the fractures (horizontal bedding planes and vertical cracks probably due to tectonic movements) which were already present in the layered limestone bedrock.

- The rock type determined the resultant morphology of the canyon. The first part features 10-12m high waterfalls, channels, and terraces due to the plucking of the boulders. The latter part features sediment islands which are considered to be characteristic of large flood events.

Caveat: Is this a really megaflood (floods with a flow of1 million cubic metres per second) per se?

References:
Lamb, M., & Fonstad, M. (2010). Rapid formation of a modern bedrock canyon by a single flood event Nature Geoscience, 3 (7), 477-481 DOI: 10.1038/ngeo894

http://media.caltech.edu/press_releases/13357

The modest Vetiver

Bountiful Nature certainly holds the antidote to many anthropogenic and natural problems. One such is Vetiver (Chrysopogon zizanioides), formerly known as Vetiveria zizanioides, a xerophytic and hydrophytic perennial clump grass of the Poaceae family with fast-growing tough root system and the ability to grow very tall with rigid stems and leaves. Since it is native to India, we tend to be quite familiar with its myriads of uses as listed below.

Vetiver roots’ aromatic and cooling properties
Vetiver’s roots are highly aromatic, with a pleasant, cool, refreshing, and earthy smell.
1. The roots are added to water in earthen pots in order to impart a distinctive flavour as well as a cooling effect.
2. The roots are kept in cupboards so that the clothes have a ‘fresh’ smell (similar to how we use sachets of lavender).
3. The fragrant essential oil from the roots is widely used in perfumery.
4. Mats and fans made of woven Vetiver roots are used to cool rooms during summer.
5. Other handicrafts made of Vetiver roots are popular due to the subtle aroma.

Medicinal property
Vetiver is often used in Ayurveda, the traditional (and viable) Indian system of medicine.
1. Water is purified by adding the roots.
2. Infusion of the roots can help in allaying fever, inflammation, and tummy problems.
3. It is effective in normalising, moisturising, and rejuvenating the skin. Apparently, it is also effective in removing acne and can be applied on irritated, wounded, and inflamed skin for speedier healing.
4. When applied regularly, the oil can prevent stretch marks (especially during pregnancy).
5. Due to its beneficial effects on the central nervous system, applying the oil also helps in psychological and emotional balance- i.e. helps in overcoming depression, stress, tension, anxiety, nervousness, and even insomnia.
6. When applied locally, it is effective in countering rheumatism, back pain, headaches, and sprains.
7. And apparently, the oil is also an aphrodisiac.

Vetiver roots’ decontaminating property
1. Vetiver decontaminates the polluted/contaminated soil.
2. As mentioned before, the roots have the property of purifying water. Being a hydrophyte, the plant can be used in treating wastewater.

For addressing environmental problems
Vetiver’s roots are unique- these grow very deep downwards and are thick with high tensile strength. As a result, it has the following uses:
1. For controlling erosion: Vetiver is very effective in preventing soil erosion when planted on the boundaries of agricultural lands, dikes, bunds, embankments, slopes, or on stream and river banks.
2. Runoffs are mostly blocked and spread in the surrounding areas. As a result, not only are the soil, sediments, and agricultural fertilisers trapped (thus enriching the land), but the soil moisture is also conserved (which the plants use during times of water scarcity).
3. Groundwater recharge- apparently, groundwater levels have increased in areas where vetiver is widely used.
4. Since Vetiver grows in clumps, weed invasion is prevented.

Vetiver requires minimal maintenance and has very sturdy characteristics. It is highly tolerant of adverse climatic conditions and variations (including droughts, floods, submergence, and extreme temperatures from -14ºC to +55ºC), pH (from 3.3 to 12.5), salinity, frosts, herbicides, pesticides, and pollutants. Its sturdy stems can withstand deep and heavy water flows. It is also noninvasive, propagating by small offsets instead of stolons or rhizomes. Should there be any fires or heavy grazing (or any other hazard), the new shoots easily develop from the underground crown. Interestingly, Vetiver is intolerant to shade which may result in a reduction of growth or even its elimination.

Vetiver is thus a low-cost effective solution to myriads of problems, including soil erosion which otherwise results in great expenses. For the farmers, this is a very beneficial tool which evidently results in increased crop yields, irrespective of adverse weather conditions. Furthermore, flooding risks are greatly reduced and runoffs of agricultural chemicals (into streams/rivers) are restricted. Even the rest of us are blessed by this modest grass!

Photo: by treesftf

Gossamer Webs 1.1

This is a new series of Our Gossamer Planet posts which will predominantly comprise of links to news articles, posts, and websites which fall under the wide scope of this blog. The chances are that it would be an eclectic mix, but obviously those which will excite your grey cells or make you ponder!

Cats and Toxoplasma gondii

Wiper fuilds and Legionnaire's Disease??? Read on....!

A literal case of butterflies in the tummy. Or is it insects?
Perhaps it is nothing to be squeamish about... after all, some of us do eat prawns (Phylum: Arthropoda; Subphylum: Crustacea)

Erosion- how a canyon was carved in three days!

If you want to listen to the Sun's melody...