Harbor Act of March 3, 1879, which provided for rehabilitation of the original 5 locks and dams built by the Commonwealth of Kentucky during the period 1835 to 1844, inclusive, and subsequent construction of additional facilities. Between 1888 and 1917 9 more locks and dams were completed thus making a total of 14 and bringing under control approximately 260 miles of slack water for the benefit of navigation. Only meager terminal facilities exist for handling mer chandise and miscellaneous freight. Following the completion of the improvements, the river carried considerable commerce throughout its length; however, commerce has decreased very materially in recent years. A detailed description of the existing navigation project and a discussion of the utilization of the project are presented in section IX C. III. METEOROLOGY AND HYDROLOGY PRECIPITATION 1 a 21. Records available.-Meteorological data are available from the records of 37 United States Weather Bureau stations located in and near the Kentucky River Basin. Pertinent information on these stations is tabulated in table 1 of appendix B and the locations of them are shown on plate 1. The stations have elevations ranging from 8 low of 422 feet to a high of 1,566 feet (mean sea level). Their periods of record vary from 2 years (Oneida and Winchester, Ky.) to 81 years (Lexington, Ky.). There is a noted concentration of stations along the main stream and the North and South Forks, with a correspondo ing lack of stations in outlying extremes of the watershed and in the drainage basins of Middle Fork, Red River, and Elkhorn and Eagle Creeks. The unequal distribution of the stations, and the intermittency and short duration of records at many of them leave mucharka to be desired. 1. TESTA 22. Rainfall. The Kentucky River Basin experiences a mean annual rainfall of about 45 inches, varying from approximately 44 inches in the northern section to 48 inches in the southern part of the watershed. The mean monthly precipitation varies from a minimum of 2.93 inches recorded in October, to a maximum of 4.47, recorded in r July. The extremes of precipitation vary from a maximum of 22.72 inches in January to a minimum of 0.11 inches in October. The maximum yearly precipitation recorded within the basin was 68.10 inches at Quicksand in 1935. The minimum for any year, 17.49 inches, occurred at Carrollton in 1901. Table No. 8-A below shows the distribution of rainfall throughout the year for the basin as a whole, the maximum and minimum values being for individual sta tions and the mean values being applicable to the basin as a whole. A break-down of this rainfall by sections of the watershed is shown in table 5 of appendix B.1 1 Not printed. Fest or Vest to urtar 25. P No.3.8 Set pr 23. Snowfall.-Average snowfall over the basin approximates 16 inches yearly. The middle and southern portions have more than the less elevated northern section (see table 3, appendix B). Snow and ice cover the ground for relatively short periods. The absence of winter-long deposits undoubtedly prevents higher winter and spring floods. 24. Types of storms.-The Kentucky River Basin' is subject to two distinct types of storms, each of which creates its respective flood problems. In the first type, very limited areas may experience flash floods from late spring to early fall because of extremely intense rainfall from thunderstorms or cloudbursts, either of which may assume cyclonic characteristics. In the second type, less limited areas may experience major floods during the winter and early spring months because of heavy precipitation from a comparatively lengthy single storm or from a sufficiently close succession of individual storms. Due principally to its geographical location, the State of Kentucky in general, and the Kentucky River Basin in particular, has been remarkably free from having major storms center over it. From plate 6 it may be seen that the watershed is long and narrow, and that most tributaries, like the main stream itself, flow toward the northwest or west. The usual path of major storms is from west or southwest to northeast, or transverse to the major axis of the basin. Furthermore, areas of storm intensities have long, narrow patterns whose major axes are parallel to the direction of storm approaches; i. e., transverse also to the major axis of the basin. Thus the Kentucky River lies athwart the usual direction of approach of its major storms and their axes of excessive rainfall areas. This condition not only reduces the probability of having major storms occur simultaneously throughout the entire watershed, but also minimizes the possibility of having them follow their own flood waves down the valley. (For further discussion see appendix B.) 1 1 25. Past storms.-Prior to 1934, only one storm (that of December 1924) out of 280 studied by the Miami conservancy district (reference No. 3, appendix A)1 centered over the State of Kentucky, and none 1 Not printed. centered over the Kentucky River Basin. During the great storm of March 23-27, 1913, which centered primarily over the region in Ohio and Indiana drained by the Miami, Scioto, and Wabash Rivers, a secondary center developed in the south central portion of the Kentucky River Basin in the vicinity of Berea. From this storm the basin experienced rainfall varying from 3.5 to 7.0 inches. Subsequent to the period studied (through 1933) by the conservancy district, three storms of considerable magnitude have occurred with main or secondary centers developing over the Kentucky River watershed. The storm causing the unprecedented flood of January 1937 in the Ohio River basin was in reality a rapid succession of individual storms which culminated in the final intense storm of January 20-25. From the successive storms prior to January 20, precipitation averaged about 6.5 inches over the Kentucky River Basin. The final storm, centering over western Kentucky and Tennessee with a maximum rainfall of 14 inches, resulted in precipitation of from 4 inches in the headwaters to 10 inches near the mouth of the Kentucky River. The storm period of January and February 1939 actually comprised two separate storms, one during January fo 29-31 and the other during February 1-4. Precipitation for the entire period averaged 4.9 inches over the basin, ranging from 3.5 inches near the northern and southern limits to 7.0 inches in the vicinity of lock No. 13. The foregoing storms (1913, 1937, and 1939) are typical of the second type mentioned in paragraph 24 above.ds Indicative of the first type is the storm of July 4-5, 1939. This storm was characterized by intense precipitation over a definitely limited area and by almost continuous electrical disturbances. No United States Weather Bureau stations were located in the vicinity of the storm centers (one near Wilhurst and Van Cleve north of Jackson and the other near Morehead outside the basin), but the storm intensity is indicated from the fact that 7.35 inches of rainfall in 11⁄2 hours was recorded at the Morehead Civilian Conservation Corps camp. Although little or no recorded data are available, it appears that other severe storms of similar character have occurred. Past storms in the basin are discussed in detail in appendix B.1 Battent 26. Maximum probable storm.-Determination of the maximum probable storm is important in estimating maximum probable and spillway design ficods. Three delimiting elements prerequisite to flood study are: (a) The total volume of precipitation, (b) its duration, and (c) distribution. The time-area-depth relations herein utilized in connection with (a) above, were obtained from a compre hensive study recently made by this office, of the maximum probable storm over the general region of the western part of the State of Ohio and the eastern part of the Commonwealth of Kentucky. For the combined purposes of reducing the required studies and computations sufficiently to come within the purview of this report, maintaining uniformity among computations, and providing certain required minimum tolerances for design purposes, a storm duration of 5 days was adopted for all drainage areas. It is believed that this encom passes what would be the critical storm period derived by other more involved methods. Values for representative areas and storm durs tion are presented in table No. 9 below. The characteristics of the maximum probable storm and pertinent data thereon are presented in appendix B,1 1 Not printed. 3. Fa Ceca are stat exte 141 coul over and arcation TABLE NO. 9.-Time-Depth--Area relation for seasonal storms, maximum probable 500 Kentucky do. do. do 5.1 2.3 9.4 5.4 13. 4 9.9 16. 1 12.8 19.5 16.2 Drain age area (square Drainage area in square miles 1,000 4.5 2.2 8.3 5.1 12.3 9.5 14.9 12.4 18.0 15.6 NOTE.-Precipitation values are average depths (in inches) over area. 1 Estimated. 2 Negligible. Stages only, no reliable estimates of flow available. Period of record 2,000 5,400 1925 to date.. 1925 to date 3,948 1909 to date. 1929-31; 1938 to date. 3.8 2.0 7.2 4.8 11.0 9.1 13. 2 11.9 16.0 15.0 RUN-OFF 27. Run-off records.-Records of stream flow and stages are reasonably complete for the Kentucky River proper but are relatively incomplete for the tributaries. These data are obtained from approximately 22 stations. At many stations, stream flow and stage records are intermittent and of short duration. Furthermore, many of the stations have not been rated, or the rating extends only to moderate flows. Almost inevitably it follows that, from their short duration, the records contain no data on major storms. The following table gives pertinent data on typical stations within the watershed. Tables Nos. 12 and 13 of appendix B,' present statistical data on all of the stations. TABLE NO. 10.-Run-off data 3.1 2.0 6. 1 7,000 5, 500 1,100 320 1,000 240 500 4.5 9.5 8.7 11.5 11.6 13.9 14.6 Average Maximum 119, 700 86, 500 (3) Minimum daily (cubic feet per second) 130 110 14 .7 .1 3.7 28. Factors affecting flood run-off.-The more extensive floods of the basin are practically all caused by prolonged heavy rainfall over somewhat extended areas. Within recent years only the flood of January 1918 could be ascribed to other causes. In this instance heavy snow cover and considerable river ice contributed to the flooding, which followed heavy rainfall in limited headwater regions only. The formation of ice gorges impeded flow and accounted for damaging stages at numerous points. The headwater tributaries exhibit the flashy characteristics usually associated with streams draining mountainous country. To a lesser degree, this tendency is also exhibited by some of the lower tributaries, while, relatively, the main stream 'Not printed. is considerably more sluggish as a result of flatter slopes. The 29. Maximum probable run-off.-The maximum flood which can be expected to result from the most adverse combination of conditions must be estimated before attempting the design of flood control works. It is generally conceded that such a flood would be created only by the occurrence of the maximum probable storm over the watershed at a time when maximum run-off conditions prevail. The run-off studies herein are predicated upon factors of 100 percent for winter and 85 percent for summer run-off. Utilizing the particular flood (summer type or winter type) which yielded the maximum run-off, the resulting maximum probable flood discharges were derived for the various areas considered in this report. Estimates of maximum probable floods on the Kentucky River at Beattyville, Frankfort, and the mouth are given in table No. 11, and similar data for other areas in the basin are given in table No. 21 of appendix B.1 TABLE NO. 11.-Maximum probable flood data Total storm volume (inches). Beattyville (drainage area, 2,586 square miles) 16. 2 5 100 16.2 339,000 Frankfort 15.5 5 100 15.5 520,000 615.000 1 Not printed. 32 Flo 30. Past floods. Individual major floods rarely, if ever, extend throughout the entire Kentucky River watershed at any one time. being usually confined to various reaches along the main stream or its tributaries. Several floods must be included in any reference to the maximum of record, since one flood may have attained maximum stage in certain reaches while floods of entirely different dates supplied these stages elsewhere. A complete flood history of the Kentucky River Basin would probably show that it has been flooded quite frequently. Historical knowledge of floods dates back to 1817, while modern records begin in 1894. From historical data it is indicated sta that many of the floods antedating modern records approached, and some may have exceeded, the maximum of modern record. Table No. 12 lists observed crest stages at representative points in the Not printed. |