If If yoa no longer need this publication write to the Geological Survey in Washington for an official mailing label to use in returning it UNITED STATES DEPARTMENT OF THE INTERIOR K::'::3 FILES iKICLCaY FLOODS IN COLORADO GEOLOGICAL SURVEY WATER-SUPPLY PAPER 997 UNITED STATES DEPARTMENT OF THE INTERIOR J. A. Krug, Secretary GEOLOGICAL SURVEY W. E. Wrather, Director Water-Supply Paper 997 FLOODS IN COLORADO BY ROBERT FOLLANSBEE AND LEON R. SAWYER UNITED STATES GOVERNMENT PRINTING OFFICE WASHINGTON : 1948 For sale by the Superintendent of Documents, U. S. Government Printing Office, Washington 25. D. C. Price 40 cents CONTENTS Page Abstract _______________---_----------.-------- _________________ 1 Introduction. _ ________________________________ _ __.- ______ 2 Acknowledgments. ______-_____---__----_---------------------_---.' 2 Previous flood investigations________________________________________ 3 Geological Survey______________________________ _____________ 3 State Engineer of Colorado ____________________________________ 4 City of Denver--__________-____--_-_-------------------___-_-_ 4 Occurrence of floods_____-____-----_-----------------------------__ 4 Topographic zones___________________________________________ 5 Influence of topography on precipitation _________________________ 5 Areas subject to floods_________________-_______________________ 7 Methods of measuring floods________________________________________ 9 Meteorologic conditions causing major floods ______________________ 10 1844____________. 10 June 1864.____--___--_-------_--------------. -._-_-_----._ 12 May 21-23, 1876._.__ - -_.........__._ 13 June 1884____-_-__ ._ - - .... 14 May 29-June 1, 1894________.__ ._ . _________ 15 September 3-6, 1909____________.__.._______.____ 16 October 4-6, 1911...__________---_______________ 17 June 2-7, 1921______________.....____________ 19 Cloudbursts..-.______________________________________ 22 Precipitation records-____________-_-__-____________________ 22 Major floods..-_________-_-_------_----_---------__--_-_-_--______ 23 South Platte River____-__----__---__----_-______-.-_._____ 23 Bear Creek-____----_-----_--------------_._---_---____.__ 30 Clear Creek.___.____----__--___-_-_.-._________________ 35 Sc. Vrain Creek_-_-__-_.-_.--___-_-__.---_.-____-____.____ 38 Lefthand Creek_______________________________________ 41 Boulder Creek________________________________________ 41 South Boulder Creek______________________________ 44 Thompson River---__-----_--------_-_---___-___-_________ 46 Buckhorn Creek__.____________________________________ 49 Cache la Poudre River.____________________________________ 51 Cherry Creek-___-___-.___._--__-._---------.--.________ 59 Kiowa and Bijou Creeks ___________________________________ 68 Republican River_____________________________________________ 72 Arkansas River.______________________________________________ 72 Grape Creek__________-____--___---_______________________ 84 Wilson Creek..________________.--_-______--____________ 84 Fountain Creek.__________________________________________ 85 Comparison of floods___________________________________ 92 Templeton Gap_______________________________._______ 93 Hogans Gulch________________________________________ 94 St. Charles River.._ __._____________ 94 Chico Greek.._-.__.-.________._.________._______ 95 IV CONTENTS Major floods Continued. Arkansas River Continued. Page Huerfano River_______________ _ ____ __ _____ 96 Apishapa River___________ ___ __ _ 99 Purgatoire River________________ _____ ____ ___________ 100 Wolf Creek and Granada Creek__________________ 111 Two Butte Creek____________________,__________ 112 Wild Horse Creek _____________________________ 112 Minor tributaries of Arkansas River________________________ 113 Rio Grande______________________________________ 114 South Fork Rio Grande_______ _ _____________ 120 Alamosa Creek__________ ___ ______________ 121 Conejos River______________________________________ 122 Colorado River___________________________________ 123 Gunnison River_______________________________________ 126 Uncompahgre River__________ _______________________ 128 Dolores River_______________________________ 129 West Creek_____________________________ 130 San Miguel River___-_____________________________ 131 San Juan River_________________ _______________ ____ 132 Animas River___________________________________ 136 La Plata River___________ _______________ 139 Summary of maximum flood discharges_____________________________ 140 Changes in channel capacity and development of flood-protection measures 146 Index__________________________ _.____-_.___ 149 ILLUSTRATIONS Page PLATE 1. City of Denver during the flood of May 19-20, 1864_______ 84 2. Damage to Denver & Rio Grande Railroad caused by flood of June 1921: A, Bridge west of Pueblo; B, Railroad yards in Pueblo. ________________________________ 85 3. Damage to tracks of Denver & Rio Grande Railroad caused by flood of October 1911 on San Juan River near Pagosa Junction. 140 FIGURE 1. Map of Colorado showing principal river systems and cities mentioned in the text--- ______________ _________ 6 2. Typical stage hy drographs of cloudbu rst floods ______________ 8 3. Chart showing maximum flood discharge, in second-feet per square mile, for various places given in the summary table__ 141 FLOODS IN COLORADO BY ROBERT FOLLANSBEE AND LEON R. SAWYER ABSTRACT The first records of floods in Colorado antedated the settlement of the State by about 30 years. These were records of floods on the Arkansas and Republican Rivers in 1826. Other floods noted by traders, hunters and emigrants, some of whom were on their way to the Far West, occurred in 1844 on the Arkansas River, and by inference on the South Platte River. Other early floods were those on the Purgatoire, the Lower Arkansas, and the San Juan Rivers about 1859. The most serious flood since settlement began was that on the Arkansas River during June 1921, which caused the loss of about 100 lives and an estimated property loss of $19,000,000. Many floods of Ipsser magnitude have occurred, and some of these have caused loss of life and very considerable property damage. Topography is the chief factor in determining the location of storms and re­ sulting floods. These occur most frequently on the eastern slope of the Front Range. In the mountains farther west precipitation is insufficient to cause floods except during periods of melting snow, in June. In the southwestern part of the State, where precipitation during periods of melting snow is insufficient to cause floods, the severest floods yet experienced resulted from heavy rains in September 1909 and October 1911. In the eastern foothills region, usually below an altitude of about 7,500 feet and extending for a distance of about 50 miles east of the mountains, is a zone subject to rainfalls of great intensity known as cloudbursts. These cloudbursts are of short duration and are confined to very small areas. At times the intensity is so great as to make breathing difficult for those exposed to a storm. The areas of intense rainfall are so small that Weather Bureau precipitation stations have not been located in them. Local residents, being cloudburst conscious, frequently measure the rainfall in receptacles in their yards, and such records constitute the only source of information regarding the intensity. A flood resulting from a cloudburst rises so quickly that it is usually described as a "wall of water." It has a peak duration of only a few minutes, followed by a rapid subsidence. Nearly 90 cloudburst floods in Colorado are described in varying detail in this report. The earliest recorded cloudburst called at that time a waterspout occurred in Golden Gate Gulch, July 14, 1872. The "wall of water" was described as a "perpendicular breast of 10 or 12 feet." A cloudburst flood on Kiowa Creek in May 1878 caused the loss of a standard-gage locomotive, and although search was made by means of long metallic rods, the locomotive was never recovered, as bedrock was about 50 feet below the creek bed. All available information relative to floods in Colorado, beginning with the flood of 1826 on the Arkansas River, is presented in this report, although for many of the earlier floods estimates of discharge are lacking. Floods throughout a large part of the State have occurred in 1844, June 1864, June 1884, May 1894, and June 1921. The highest floods of record were on the 1 2 FLOODS IN COLORADO larger streams and occurred as follows: South Platte River, June 1921; Rio Grande, June 1927; Colorado River, June and July 1884; San Juan River, October 1911. The greatest floods on the plains streams occurred during May and June 1935 and were caused by cloudbursts. Ranchers living in the vicinity noted rainfalls as high as 24 inches in a 13-hour period, measurements being made in a stock tank. The effect of settlement on channel capacities can be clearly traced. When settlement began, and with it the beginning of the livestock industry, the plains were thickly covered with a luxuriant growth of grasses. With the development of the livestock industry the grass cover was grazed so closely that it afforded little protection against erosion during the violent rains and resulting floods. The intensive grazing packed the soil so hard as to increase greatly the percentage of rainfall that entered the streams. This condition was noted during the Arkansas River flood of October 1908, when an estimated two-thirds of the 6-inch rainfall appeared almost immediately in the nearby streams.