UNITED STATES DEPARTMENT OP THE INTERKT J. A. Krug, Secretary GEOl-OGICAL SURVEY , W. & Wrather, Director Water-Supply Paper 1046 TEXAS FLOODS OF 1940 BY . ' *" SETH D. BREEDING »ntt UNITED STATES GOVERNMENT PRINTING OFFICE WASHINGTON : 1948 For sale by the Superintendent of Documents, U. S. Government Printing Office, Washington 25, D. C. CONTENTS Page Abstract ____ -___ -. 1 Introduction _____ ___. 2 Administration and personnel________ __________ 3 Acknowledgments __ __ 4 Measurement of flood discharges... ____ _____________ 4 June-July floods in south-central Texas ____ _ __ 5 Rainfall.-______.. _____ __ 8 Flood stages and discharges 15 Summary of flood stages and discharges 18 Stages and discharges at stream-gaging stations__ ________ 18 Brazos River Basin,______ __ ________ 27 Brazos River at Waco_ , ___ _ ___ 27 Brazos River near Marlin_ ________________________ . 29 Brazos River near Bryan______ __ ______ 30 Brazos River near Hempstead ____ __ 32 Brazos River near San Felipe__ ____ ________ 33 Brazos River at Richmond- ____ _-________ 35 Brazos River at East Columbia,_______ ________ 36 Little River at Cameron_ ___ 37 Yegua Creek near Somerville, _-___ ___________ 39 Navasota River near Easterly _ __________ _______ 40 Colorado River Basin._____ __ ____ 41 Colorado River at Austin ____ 41 Colorado River at Smithville __ _ ________ 43 Colorado River at La Grange.. ______ 44 Colorado River at Columbus_ _t ,.» ________ 46 Colorado River at Wha$to^_ __, .._ I i- '-- -.,- .» T 48 Colorado River nea>^y'Cityl___i?i__«^.-ii-l'_._s_^ 49 Dry Creek^at Btle§chei[I^ak® niftr ^mijfchySBjiifeJi-.______ 50 _ 51 Edna_ _ _ 53 Navidad River near Ganado___ 54 Guadalupe River Basin__________ . 55 Guadalupe River above Comal Eiver, at New Braunfels____ 56 Guadalupe River at Victoria 57 San Marcos River at Ottine_ ______ __ ___ 58 Coleto Creek near Victoria. __ 60 San Antonio River at Goliad_____ ___ _______ ______ 61 CONTENTS HI Page November floods in the San Jacinto River Basin _ 62 Meteorolbgie conditions._______ * *- - 63. Rainfall______________________________ 64 Stages and discharges at stream-gaging stations. * 69 San Jacinto River Basin_ - , 71 West Fork San Jacinto River near Conroe.*,. 71 West Fork San Jacinto River near Humble. * - 74 San Jacinto River near Huffman ______________________ 76 Sparing Creek near Spring-..- 1 ;, 78 Bast Fork San Jacinto River near Cleveland _ 80 Rainfall and runoff studies________________ 82 Discussion of results__--l_-____-_-___--_---_---------- _____ 83 Sediment.-__________________________________- 87 Previous floods________._______________' _ 88 Index.__________________________________________________________ 91 ILLUSTKATIONS Pact PLATE 1. Map of Texas showing major topographic divisions, major drain­ age basins, and average annual rainfall through 1939___ ___ 6 2. Typical stream-gaging stations: A, Recording gage and silt trap on Colorado River at Austin; B, Recording gage and neas- uring cableway on Colorado River at Columbus____ _.. 6 3. Lavaca River at Hallettsville, flood of June 30, 1940: At View toward highway bridge from near left edge of overflow; B, View from left bank at railway crossing_______________ 14 4. Lavaca River at Hallettsville, flood of June 30, 1940: A, View near center of business district; B, View of channel looking downstream from highway bridge after flood receded _______ 15 5; Isohyetal map of south-central Texas showing total rainfall June 28 to July 1,1940, and location of rainfall stations .___ In pocket 6. Isohyetal map of south-central Texas showing total rainfall June 28 to July 4, 1940, and location of stream-measurement points___-___________________________________ In pocket 7. A, Navidad River near Ganado at peak of flood of July 2,1940; B, San Jacinto River flood of November 27,1940, at highway crossing near Crosby________________________________ 74 FIGURE 1. Graphs of cumulative rainfall, in inches, at Cheapside, Lexing- ton, andSomerville, June29-3®, 1940._____________^ 9 2. Graphs of discharge at stream-gaging stations on upper B-azos River, June 25 to July 17, 1940 ________________ 20 3. Graphs of discharge at stream-gaging stations on lower Brazos River, June 25 to July 17, 1940__________________ 21 1 4. Graphs of discharge at stream-gaging stations on tributaries of Brazos River, June 28 to July 10, 1940___________ 22 5. Graphs of discharge at stream-gaging stations on Colorado River, June 28 to July 10, 1940________________ 23 IV CONTENTS Page FIGURE 6. Graph of discharge at stream-gaging station on Dry Creek at Buescher Lake, near Smithville, June 29 to July 1, 1940-___ 24 7. Graphs of discharge at stream-gaging stations in the Lavaca River Basin, June 28 to July 10, 1940__._-_____________ 25 8. Graphs of discharge at stream-gaging stations in the Guadalupe River Basin, June 28 to July 10, 1940-____-_______-__--_- 26 9. Isohyetal map of San Jacinto River Basin, Tex., showing total rainfall, in inches, November 20-26, 1940, and locations of* stream-gaging stations-. _ _______________________________ 64 10. Graphs of cumulative rainfall, in inches, at Montgomery and Shepherd, November 22-25, 1940____._______________ 68 11. Graphs of discharge at various stream-gaging stations in t^e San Jacinto River Basin, November 24 to December 20, 1940_ _ _ _ _ 70 12. Graphs of discharge at various stream-gaging station in fie San Jacinto River Basin, November 24 to December 22, 1P40___ 71 TABLES Page TABLE 1. Rainfall, in inches, June 28 to July 4, 1940__________________ 10 2. Summary of flood stages and discharges in south-central Texas for floods of June-July 1940__--___--_______.____-__----_- 16 3. Rainfall, in inches, in San Jacinto River Basin and adjacent areas, November 20-26,1940_______-______-______--_---_- 66 4. Rainfall and direct runoff of storm of June 28 to July 4, 1940, for certain areas in the Colorado and Lavaca River Basins._____ 84 5. Rainfall and direct runoff of storm of November 20-26, 1P40, in San Jacinto River Basin_________________________----____ 86 6. Silt load and runoff at measurement stations on West Fork San Jacinto, Brazos, and Colorado Rivers during flood periods, 1940________________________________- 88 TEXAS FLOODS OF 1940 By SETH D. BREEDING ABSTRACT Floods occurred'in T6xas during June, July, and November 1940, fcHt exceeded known stages on many small streams and at a few places on the larger streams. Stages at several stream-gaging stations exceeded the maximum known at those places since the collection of daily records began. A storm, haying its axis generally on a north-south line from Cameron to Vic­ toria and extending across the Brazos, Colorado, Lavaca, and Guadalupe River Basins, caused heavy rainfall over a large part of south-central Texas. The maximum recorded rain of 22.7 inches for the 2-day period June 29-30 occurred at Engle. Of this amount, 17.5 inches fell in the 12-hour period between 8 p. m. June 29, and 8 a. m. June 30. Light rains fell at a number of places on June 28, and additional light rains fell at many places within the area from July 1 to 4. During the period June 28 to July 4 more than 20 inches of rain fell over an area of 300 square miles, more than 15 inches over 1,920 square miles, ani more than 10 inches over 5,100 square miles. The average annual rainfall for the area experiencing the heaviest rainfall during this storm is about 35 inches. Farming is largely confined to the fertile flood plains in much of the area sub­ jected to the record-breaking floods in June and July. Therefore these floods, coming at the height of the growing season, caused severe losses to crops. Much damage was done also to highways and railways. The city of Hallettsville suffered the greatest damage of any urbar area. The Lavaca River at that place reached a stage 8 feet higher than ever known before, drowned several people, destroyed many homes, and submerged almost the entire business district. The maximum discharge there was 93,10C second-feet from a drainage area of, 101 square miles. Dry Creek near Sm thville produced a maximum discharge of 1,870 second- feet from an area of 1.48 square miles and a runoff of 11.3 inches in a 2-day period from a rainfall of 19.5 inches. The area in the Colorado River Basin between Smithville and La Grange, amounting to 550 square miles, had an average rainfall of 19.3 inctes, of which 11.5 inches appeared as runoff. The maximum discharge at La Grange was 182,000 second-feet, with much the greater part coming from below Smithville. This is probably a record-breaking flood for the area between Smithville and La Grange, but stages as much as 16 feet higher have occurred at La Grange. Heavy rainfall over the east half of Texas November 21-26 caused lafge floods in all streams in Texas east of the Guadalupe Riiver. The maximum recorded rainfall for the 2-day period November 24-25 was 20.46 inches at Hempstead, of which 16.00 inches fell in 24 hours or less. The storm occurred during the period November 20-26, with the greater part of the rain falling November 23-25. During the period November 20-26, rainfall in Texas amounted to more than 15 inches over an area of 3,380 square miles, and "to more than 10 inches oveof an eetea, of 17,570 square miles. The average annual rainfall for the area in Texas experiencing more than 10 inches of rain during,this storm ranges from 2 TEXAS FLOODS OF 1940 SOjinches on the east border of the State to 35 inches near the west edge of the area.