The real cause of flooding

THE EDITOR: The extensive damage caused by heavy rainfall in recent times is due to a large extent to the change of weather patterns taking place all over the world. This is caused by a temperate inversion. In Trinidad and Tobago it is no different. The consensus of opinions entertained by both Government and Opposition, centres around the cutting of trees on the hills to make way for building development; indiscriminate dumping of rubbish in water courses, combined with the silting of culverts, reduced the effective use of the water-ways. It is claimed that these conditions are mainly responsible for the disastrous floods. I beg to differ. “It is the large volume of water,” in the rocky uplands of the Northern and Central ranges, which contain the swell of water.

It is a matter of simple observation that show the streams in the sub-catchments form only a small part of the vast network of streams within the large catchment area, which serves the “main rivers.” For most of the year these streams remain relatively dry except during the time of heavy rainfall. In the case of existing culverts, they have proved their sufficiency and capability of taking care of the flow resulting from all ordinary floods. When it comes to prone areas subjected to flooding, such as Caroni, the Central Range is the main source of supply. At a time of heavy rains, when this volume of water breaks loose, it flows into the lowlands of the Caroni Plains.

The southern highway in the vicinity being an obstruction forms a weir, or dam to the free flow of water. The head of water created will rise, thus rendering all courses and culverts ineffective regardless of their size. Some experiments were conducted over a number of years and when represented on a graph showed that a co-efficient of one was deemed proper for conditions of steep and rocky ground where the run-off is greatest. For areas in square miles: one, two, three and four, the culvert opening should be: 127, 210, 310 and 355 square feet respectfully. Beyond this, it is not considered necessary to provide for phenomenal floods, which occur at long intervals of time.

Even empirical data cannot provide answers, yet the “know-alls” expect the Government to perform miracles in putting an end to flooding. They dare not blame God, lest they be denied the fruits of paradise. To ban development on the hills and other places would be a mistake. Needed however, is the creation of wider water-ways, one or more culverts joined together, instead of raising the road ways to the Caroni river bridge and elsewhere. It is therefore essential for the Works and Transport Minister to explore thoroughly the difference between a dam and a reservoir, before making financial commitments. Often one learns more from failures than from successful undertakings. Flooding is for real.

W CRAIGWELL
Valsayn