Deluge in the Indian-Kentuck Basin: 1908

The streams in Jefferson County, and probably much of Southern Indiana, once ran clear after storms, my grandfather once said. It was deforestation that turn caused them to turn muddy as they now do. And it was deforestation that produced alternating dry creek beds and raging torrents that drove mills out of business. The forests had once released water slowly, ensuring a steady flow much of the year. This paper by Professor Glenn Culbertson, whose family came from the Scottish settlement in the upper reached of the Indian-Kentuck basin, described an unusual cloudburst whose effects he attributed to the deforestation.


The Twenty-fourth Annual Meeting Of The Indiana Academy Of Science.

The twenty-fourth annual meeting of the Indiana Academy of Science was held at Purdue University. Lafayette, Indiana. Thursday. Friday and Saturday. November 26, 27 and 28. 1908.

Furthermore, we believe that it can be shown that deforestation has a tendency in a region of rough topography, such as is found among the hills of southern Indiana, to localize the hot season rainfall, and to produce conditions approximating those of the so-called "cloudbursts" of the Rocky Mountain regions of the West. A case in point occurred during the past summer in the latter part of July over an area of some six or eight square miles along the divide between the basins of Indian Kentucky and Indian creeks and their tributaries, in eastern Jefferson and western Switzerland counties of this State. The rainfall in this case was unprecedented for the region.

On one border of the given area a government rain gauge, kept by J. R. Shaw, Jr., was filled to the brim, the measurement amounting to three and one-half inches, and then ran over for an unknown period. Afterward the gauge was emptied and received one and one-half inches more, making at the least live inches, and probably much more, in the period of two hours during which the rain fell. Other and more reliable measurements in locations more nearly the center of the storm area were made and a precipitation of at least ten inches in the two-hour period were recorded.

The conditions producing this exceptional and very destructive rainstorm were as follows: The region to the west and southwest of the storm-swept region is one of the roughest topographically in southern Indiana. The whole area for ten or twelve miles in this direction forms the basin of Indian Kentucky Creek and tributaries, and the hills rise in many instances 400 to 450 feet above the valleys, and the slopes are very steep. From the whole basin the forests have been almost entirely removed.

On the day referred to the temperature was unusually high, some thermometers within the area registering 102 degrees in the shade. There was no movement of the air until early in the afternoon, when a gentle southwest wind arose, and this caused the highly-heated air of the whole region to move northeastward. The valley of Brushy-fork Creek, one of the principal tributaries of Indian Kentucky Creek, became the center of the air movement.

About three in the afternoon a cloud began to form above the divide and around the head of the valley of Brushy-fork Creek. The highly-heated air ascended very rapidly on reaching the divide, and the consequent rapid cooling of the air by expansion caused an equally rapid condensation of the moisture of the air. The cloud increased in volume with very great swiftness, and the rain fell in torrents, first over a very limited area and then over a wider region. The center of the storm, however, instead of moving, as is usually the case, remained almost stationary for a period of two hours. During this time the winds from almost the entire surrounding region moved slowly towards the now enlarged area of precipitation. There were few if any clouds outside of the six or eight square miles covered by the storm, but the hot air from the proximity, on reaching this area of rapidly rising atmosphere, constantly added its moisture to that being condensed, with the result that for two hours the downpour continued.

This very unusual precipitation proved exceedingly disastrous to the soil of the cultivated fields, and to the roads and bridges as well as to property of all kinds along Brushy Fork Creek and the larger tributaries of Indian Creek. Both of these streams were several feet above any previous record. Where a few moments before there were dry, rocky creek beds, now became a wild flood from six to ten feet in depth and from 300 to 500 feet wide. Buildings were carried away that had seldom or never been touched by previous floods.

In the opinion of the writer this cloudburst, which in truth it was, was caused by the intense heating of the deforested region of very rough topography to the southwest, followed by the gentle movement of great volumes of heated air in a northeasterly direction, until in its passage over the divide it rapidly ascended. Becoming cooled in its ascent, the enormous quantity of moisture held in the highly-heated atmosphere rapidly condensed, and the unprecedented rainfall for that region followed.

It may be years before conditions of temperature, moisture and winds would unite to produce another such storm in the same locality, yet the probabilities are that in the future such rainfalls will become increasingly frequent somewhere in such deforested areas of rough topography.