Floods of April 28, 1966 In the Northern Part of Dallas, Texas

Transcription

1 Floods of April 28, 1966 In the Northern Part of Dallas, Texas GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1870-B Prepared in cooperation with the city of Dallas

2 Floods of April 28, 1966 In the Northern Part of Dallas, Texas By WILLARD B. MILLS and ELMER E. SCHROEDER FLOODS OF 1966 IN THE UNITED STATES GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1870-B Prepared in cooperation with the city of Dallas UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1969

3 UNITED STATES DEPARTMENT OF THE INTERIOR WALTER J. HICKEL, Secretary GEOLOGICAL SURVEY William T. Pecora, Director For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C

4 CONTENTS Page Abstract Bl Introduction. 1 Acknowledgments 2 The study area 2 Flood history. 11 Rainfall 12 Antecedent rainfall 12 Rainfall on April 28, General description of the April 28, 1966, flood 19 Inundation 22 Flood damage. 23 Determination of flood discharge. 23 Summary 24 Streamflow data _-_ Explanation of data. 27 Station data. 29 Joes Creek at Walnut Hill Lane, Dallas, Tex. 29 Joes Creek at State Highway 114, Dallas, Tex 29 Bachman Branch at Walnut Hill Lane, Dallas, Tex 30 Slaughter Branch at Walnut Hill Lane, Dallas, Tex 30 Bachman Branch at Northwest Highway, Dallas, Tex 30 Bachman Branch at Midway Road, Dallas, Tex 31 Bachman Branch at Webbs Chapel Road, Dallas, Tex 31 Bachman Branch at Bachman Lake, Dallas, Tex 31 Turtle Creek below McFarlin Boulevard, Dallas, Tex 32 Turtle Creek at Dallas, Tex.. -_-_ White Rock Creek at Keller Springs Road, Dallas, Tex 32 Spanky Branch at McCallum Lane, Dallas, Tex Armstrong Branch at Melrose Drive, Richardson, Tex 33 Cottonwood Creek at Forest Lane, Dallas, Tex Floyd Branch at Valley View Road, Dallas, Tex 34 Floyd Branch at Forest Lane, Dallas, Tex 34 White Rock Creek at Greenville Avenue, Dallas, Tex 34 White Rock Creek at White Rock Lake, Dallas, Tex 35 Ash Creek at Highland Drive, Dallas, Tex 35 Forney Creek at Lawnview Avenue, Dallas, Tex 36 White Rock Creek at Scyene Road, Dallas, Tex 36 Selected references.. 37 m

5 IV CONTENTS ILLUSTRATIONS Page PLATE 1. Map showing areas flooded in the north Dallas area, Texas. In pocket 2. Maps and graphs showing cumulative rainfall at 30- minute intervals and total rainfall for the storm of April 28, 1966, north Dallas area, Texas In pocket FIGURE 1. Map showing location of watersheds. B Flood profiles: 2. Joes Creek Bachman Branch Turtle Creek 8 5. Upper White Rock Creek 9 6. Cottonwood Creek Floyd Branch- -_ Graph showing accumulated rainfall, April 13-28, 1966, at rain gage 6-W Graph showing comparison of maximum point rainfall intensity at gage 12-W with the rainfall intensityduration-frequency curves for Dallas Graphs showing comparison of rainfall intensities on watersheds with the rainfall intensity-durationfrequency curves for Dallas: 10. Bachman Branch watershed Joes Creek watershed Turtle Creek watershed Rainfall-runoff hydrographs for storm on Joes Creek and Bachman Branch watersheds Rainfall-runoff hydrographs for storm on Turtle Creek and White Rock Creek watersheds Photographs of flood damage: 15. Joes Creek at Walnut Hill Lane. _-_-. _ Bachman Branch Turtle Creek at Fitzhugh Avenue Photograph of flooding on White Rock Creek at Scyene Road TABLE Page TABLE 1. Flood stages and discharges B28

6 FLOODS OF 1966 IN THE UNITED STATES FLOODS OF APRIL 28, 1966, IN THE NORTHERN PART OF DALLAS, TEXAS By WILLARD B. MILLS AND ELMER E. SCHRQEDER ABSTRACT The floods of April 28, 1966, in the northern part of Dallas, Tex., caused heavy damage to a relatively small area. Flood damage was estimated at $2,500,000; and of this amount, $1,330,000 damage was along Bachman Branch, which has a drainage area of 12.3 square miles. At least seven persons died as a direct result of the floodwaters. The flood was caused by a 5-hour storm in the early hours of April 28. Antecedent rainfall had so saturated the area that the intense, but relatively low, total rainfall (less than a 50-year return period) caused historical floods to be exceeded at many points. A peak runoff rate of 3,160 cubic feet per second per square mile occurred on a 1.5 square-mile area within the watershed. INTRODUCTION A rainstorm in the northern part of Dallas during the early hours of April 28,1966, produced up to 6.7 inches of rain in a 6-hour period; 4.9 inches of rain fell within 1 hour. The intensity of the rainfall exceeded a 100-year return period by a considerable amount for durations of 30 minutes to 2 hours, as indicated by U.S. Weather Bureau Technical Paper 25. Because almost 8 inches of rain had fallen during the preceding 2 weeks, the watershed was well saturated, and all storage areas were full. In addition, most of the area is urbanized. This combination of intense rainfall and other hydrologic conditions favorable to high runoff resulted in flood flows greater at some points than the highest flood flows ever recorded on small streams in Dallas. A peak runoff rate of 3,160 cfs per sq mi (cubic feet per second per square mile) occurred on a 1.5 square mile area. This is the second highest peak rate of runoff per square mile recorded by the U.S. Geological Survey in Texas. The highest peak runoff rate recorded, 3,350 cfs per sq mi, occurred on June 30, 1936, on the 4.12 square mile drainage area of Bunton Branch near Kyle, 20 miles southwest of Austin. Bl

7 B2 FLOODS OF 1966 IN THE UNITED STATES Flood damage in Dallas was extensive. Bridges were washed away; more than 270 homes and at least 40 businesses were severely damaged; lawns, gardens, and cemeteries were inundated; and seven lives were lost. Flooding on Bachman Branch, one of the watersheds in north Dallas, caused damages estimated at $1,330,000. This report describes the flood event of April 28, 1966, for the following watersheds in north Dallas: Joes Creek, Bachman Branch, Turtle Creek, Cottonwood Creek, and Floyd Branch. This flood event is described in terms of rainfall (magnitude, intensity, frequency, and distribution), peak discharge at selected points, flood profiles, inundated areas, comparison with previous floods, effects of channel changes on flood profiles, and property damage and loss of life due to the flood. The flood on the main stem of White Rock Creek is also described, but in less detail. Figure 1 shows the location of the watersheds, and plate 1 shows the flooded areas. In August 1961 the U.S. Geological Survey, in cooperation with the city of Dallas, began a program of continuing investigations designed to evaluate the hydrologic factors affecting floods on several small streams in Dallas. Supporting data and computations are in the files of the U.S. Geological Survey, Water Resources Division, Room 647, Federal Building, 300 East 8th Street, Austin, Tex. The height of a flood at any location is generally stated in terms of the stage, which is the elevation of the water surface above a selected datum plane. In this report, flood heights (stages) are expressed in feet above mean sea level. The rate of flow of a stream is the volume of water that passes a particular point in a given period of time. Discharge rates are given in cubic feet per second. The peak discharge is the maximum instantaneous rate of flow for a given flood. ACKNOWLEDGMENTS The aid of personnel from the city of Dallas who furnished data and assistance for this report is gratefully acknowledged. H. H. Stirman, Director of Public Works, Dallas, Tex., and his staff worked closely with the field engineers to aid in collecting the most accurate data. On the morning of April 28, 1966, Public Works crews were in the flood area and flagged highwater marks. These marks were very helpful in establishing elevations for the flood profiles. THE STUDY AREA The study area comprises about 150 square miles in or near Dallas. Most of the study area is in the 136-square-mile drainage area of White Rock Creek, a tributary to the Trinity River. Because the storm

8 APRIL 28, 1966, NORTHERN PART OF DALLAS, TEXAS B3 was centered in the northern part of the city, two subwatersheds, Cotton wood Creek watershed (8.50 sq mi) and Floyd Branch watershed (4.17 sq mi), within the White Eock Creek watershed were studied in detail. The upstream part of these two watersheds is in the city limits of Richardson, north of the Dallas city limits. Three other watersheds Joes Creek, Bachman Branch, and Turtle Creek were investigated in detail '30" 47'30" '30"- FIGURE 1. Location of watersheds in flood area.

9 B4 FLOODS OF 1966 IN THE UNITED STATES Within the reaches subject to extreme flooding, the stream channels are similar in shape and capacity, even though they differ in size. Each channel generally consists of a wide flood plain along both banks in the upper reaches and a relatively narrow flood plain in the lower reaches. As tributaries approach the Trinity River, the flood plain of the Trinity River provides a wide area of overflow. Much of the flood plain is in urban areas and is covered with well-kept lawns and paved streets. The rest of the flood plain is mostly covered with natural grasses on abandoned farmland. The main channels of the major tributaries, which are generally incised to limestone bedrock, are approximate trapezoids cut into the well-compacted alluvial material. Trees and brush growth along both banks of the main channels is fairly heavy. The low-flow channels are in solid limestone and contain some sand and gravel riffles. Little scour occurred except at bridges and constrictions where a large part of the water flowed over the roads. The areas described in this report are in metropolitan Dallas. Each area has a high percentage of impervious cover. The drainage area of Joes Creek at Interstate Highway 35E is 7.51 square miles. The streambed slopes uniformly from an elevation of 633 feet at the headwater near Valley View Lane to 479 feet at Marsh Lane in a distance of 3.6 miles. In the 3.3 miles below Marsh Lane the streambed slopes uniformly from an elevation of 479 feet to 410 feet at Interstate Highway 35E. Figure 2 shows the profiles of the floods and elevations of the streambed. The drainage area of Bachman Branch is 12.3 square miles at Bachman Lake spillway and 12.6 square miles at Interstate Highway 35E. The streambed slopes uniformly from an elevation of 655 feet at the headwaters near Valley View Lane and Preston Road to 474 feet at Brookview Drive in a distance of 4.4 miles. From Brookview Drive the streambed slopes uniformly for 1.2 miles to an elevation of 447 feet at Midway Road. Beyond this point the streambed has a constantly decreasing slope to Bachman Lake, where the spillway elevation is feet. Below Bachman Lake the streambed slopes from an elevation of 419 feet to 405 feet at Interstate Highway 35E in 0.7 mile. The dam retaining Bachman Lake was built in 1901 as part of the water-supply system for Dallas. The lake, which covers about 128 acres, is at the lower end of Bachman Branch just above the confluence with Elm Fork Trinity River. Floodwater will bypass the spillway and flow around the right end (north side) of the dam when the lake water level exceeds 443 feet in elevation. Figure 3 shows the profiles of the floods and elevations of the streambed. The drainage area of Turtle Creek is 7.98 square miles at the streamgaging station 200 feet above Hall Street. The streambed slopes uniformly from an elevation of about 620 feet between Royal Lane and

10 -69 o ess-ses ELEVATION ABOVE MEAN SEA LEVEL, IN FEET tb Webbs Chapel Road (10- by 10-ft barrel added to culvert after 1962) svxai, 'svaiva.10 j,hvd '9951 ( sz

11 RIVER MILES ABOVE INTERSTATE HIGHWAY 35E FIGURE 3. Profiles of floods on Bachman Branch. EXPLANATION Flood of April 28, 1966 Flood of October 8, 1962 (actual) D April 28, 1966,floodmark October 8,1962,floodmark Channel dam Backwater from Trinity River elevation uncertain) wo5 Approximate bed of stream in 1966 A (Dashed line shows 1962 streambed) Gaging station at Midway Road. Mile 3.4

12 APRIL 28, 1966, NORTHERN PART OF DALLAS, TEXAS Walnut Hill Lane to 541 feet just downstream from Lovers Lane in a distance of about 2.8 miles. In the upper part of this reach the channel is concrete lined to Northwood Road. From Northwood Road to below Lovers Lane, the main stream channel consists of two 6- by 4- foot storm sewers. Downstream from Lovers Lane the channel drops uniformly for 3.0 miles to an elevation of 433 feet at Turtle Creek Drive. In the 1.8 miles from Turtle Creek Drive to Harry Hines Boulevard, the streambed drops uniformly 46 feet. Below Lovers Lane the channel consists mainly of a rectified channel interspersed with small dams. A large-volume pressure storm sewer (278 sq ft in cross-sectional area ranging from 18i/ ft semieliptical to a 16-ft modified horseshoe) begins at the dam below Cedar Springs Road and ends at the Trinity River. The design capacity at the elevation of the dam crest is 3,600 cf s. Figure 4 shows profile of the flood, elevation of the streambed and the dam sites. Turtle Creek watershed was completely urbanized before the streamgaging station was installed. Paved streets, well-kept lawns, and rather expensive homes cover most of the area in the watershed. White Rock Creek is in the northern and eastern parts of Dallas County. The headwaters of White Rock Creek, a tributary of the Trinity River, are about 10% miles north of the Dallas city boundary. Headwater elevations are about 780 feet. The stream flows southward about 30 miles into White Rock Lake, which has a conservation pool elevation of 458 feet. The stream continues southward from White Rock Lake for 10.3 miles to the Trinity River. From the northern city boundary of Dallas (mile 27.6) to the Texas and New Orleans Railroad Co. bridge (mile 18.7), the streambed has a nearly uniform slope of about 10 feet per mile. In the 5-mile reach between the railroad bridge and White Rock Lake, the slope decreases from a drop of about 5 feet per mile to about 2 feet per mile. The streambed slopes from the 458-foot spillway elevation to about 414 feet at Garland Road in a distance of 0.2 mile. Within 0.9 mile the streambed drops another 8 feet. Downstream from Garland Road the streambed slopes uniformly at a rate of 4.4 feet per mile. Figure 5 shows profiles of the floods and elevations of the streambed in upper White Rock Creek. The drainage area of Cottonwood Creek, a tributary to White Rock Creek that rises 1.3 miles north of Dallas County, is 8.50 square miles at Forest Lane, 0.6 mile upstream from the mouth. The streambed slopes from an elevation of 730 feet 1.5 miles north of Dallas city limits to 564 feet at Belt Line Road in a distance of about 4.6 miles. From this point the streambed slopes uniformly to an elevation of 476 feet at the mouth in a distance of 3.9 miles. Figure 6 shows profile of the flood and elevation of the streambed. B7

13 FIGURE 4. 'Profile of flood on Turtle Creek. EXPLANATION o Floodmark J Channel dam Flood of April 28, 1966 W 00 CD Approximate elevation of stream bed RIVER MILES ABOVE INTERSTATE HIGHWAY 35E

14 ELEVATION ABOVE MEAN SEA LEVEL, IN FEET g 2 ui en ui ui ui ui m Dallas //"County line- 'j_lntermediate / section fi 2 S* <» 3 a *» = T. & N. 0. Railroad /^ / Intermediate section i'/// M.K. &T. Railroad ' Loop 12 svxax 'svnva jo '996 1 'sz

15 FIGURE 6. Profile of flood on Oottonwood Greek. Floodmark Channel dam Flood of April 28, 1966 Approximate elevation of streambed 4 3 RIVER MILES ABOVE MOUTH

16 APRIL 28, 196&, NORTHERN PART OF DALLAS, TEXAS Bll The flood plain has been developed with residences and parks from Campbell Road to Spring Valley Road. Below Spring Valley Road the flood plain is not as completely developed, and a few areas are covered with native grasses, trees, or shrubs. The drainage area of Floyd Branch, which joins Cottonwood Creek about 0.6 mile upstream from the confluence of Cottonwood Creek with White Rock Creek, is 4.17 square miles at Forrest Lane, 0.3 mile upstream from the mouth. The streambed slopes uniformly from an elevation of 680 feet at the headwaters between Campbell Road and Arapaho Road to an elevation of 565 feet at the low-water crossing in the Restland Memorial Park Cemetery in a distance of about 2.9 miles. From the low-water crossing the streambed slopes uniformly for 1.1 miles to an elevation of 529 feet near the Interstate Highway 635 (LBJ Freeway). From this point the streambed slopes uniformly to an elevation of 489 feet at the mouth in a distance of 1.5 miles. Figure 7 shows the profile of the flood and elevation of the streambed. Floyd Branch is similar to Cottonwood Creek in development of the flood-plain area. Upstream from Spring Valley Road, commercial and residential building has fairly well covered the flood plain. Down stream from Valley View Road, the area is less developed. FLOOD HISTORY Previous investigations have traced the flood history of the study area back to about At that time the number of flood-recording installations was limited; consequently, much of the information for the early records was obtained by interviewing long-time residents and by reading flood accounts in old publications. This report tabulates these historical floods as recorded in preceding reports, along with pertinent remarks. (See "Notable Flood Events" below.) NOTABLE FLOOD EVENTS May 25, 1908 Flooding of the Elm Fork Trinity River produced backwater and caused severe flooding in the lower reaches of Bachman Branch and Joes Creek. Flood stages in lower reaches exceeded those of the October 8, 1962, flood. April 25, 1922 A high intensity rainfall, which followed a wet period, produced unusually high runoff from the Bachman Branch and Joes Creek watersheds. Discharges were almost equal to those of the October 8, 1962, flood. April 19-20, 1942 Heavy rainfall produced runoff reported to be the highest since at least 1886 along White Rock Creek. May 1946 Substantial runoff occurred. August Substantial runoff occurred.

17 B12 FLOODS OF 1966 IN THE UNITED STATES NOTABLE FLOOD EVENTS Continued June The city of Richardson reported 11.5 inches of rainfall in a 12-hour period. This area contains the headwaters of Cottonwood Creek and Floyd Branch. Cottonwood Creek at Forest Lane had the highest stage since April 26, 1957 Substantial runoff occurred. October 1, 1959 _. The highest stage since at least 1903 occurred at the Turtle Creek streamflow station upstream from Hall Street. July 27, 1962 _ The greatest flood since 1942 at many points in north Dallas. October 8,1962 Prior to April 28, 1966, this was the greatest headwater flood since about 1900 along Bachman Branch and Joes Creek. September 21, 1964 Flooding was severe although not recordbreaking in the five watersheds of the study area except in upper White Rock Creek. Flooding in the upper White Rock Creek watershed was the greatest known. The average rainfall for an 8-hour period was nearly 12.5 inches on the upper 29.4 square miles of the watershed, resulting in 11 inches of runoff. April 28, 1966 _ The greatest known headwater flood on Bachman Branch, Turtle Creek, Cottonwood Creek, and Floyd Branch. Flood history begins about RAINFALL ANTECEDENT RAINFALL The U.S. Weather Bureau station at Dallas recorded more rain during April 1966 than had been recorded in any month since the record began in Rain gage 6-W, in the White Eock Creek watershed, near the center of the study area, recorded inches of rain during the period April Of this amount, 7.95 inches fell prior to the April 28, 1966, storm. Figure 8 shows the accumulated rainfall from seven storms at rain gage 6-W for the period April 13-28,1966, which is typical for the study area. Because of these antecedent-rainfall conditions, which caused the ground to be saturated and all the storage areas to be full, a high percentage of rainfall from almost any storm would have become runoff. RAINFALL ON APRIL 28, 1966 The rains that caused the floods in Dallas began at about 0030 hours on the 28th of April and ceased at about 0600 hours the same day. During this interval, rainfall was intense for about 1 hour. The maximum storm rainfall occurred at rain gage 12-W, where the intensity for a 30-minute period was 6.40 inches per hour, and the hourly total was 4.92 inches. (These totals reflect the most intense rainfall and are

18 S 09H-O 0S8-S&8 ELEVATION ABOVE MEAN SEA LEVEL, IN FEET -Spring Valley Road._Low-water crossing in cemetery Cemetery maintenance-area road Valley View Lane Interstate Highway 635 (L B J Freeway) -Tobian Street -Forest Lane Z! O 33 a = 3 ' Cottonwood Creek svxai, 'sviiva ^o i,hvd NHSHI-HON '-9961 'sz IIH.IV

19 B14 FLOODS OF 1966 IN THE UNITED STATES more than the rainfall shown on plate 2 for 12-W.) Figures 9-12 show the intensity of the rainfall at various sites as compared with the intensity-duration frequency for the period at the Dallas Weather Bureau station (U.S. Weather Bureau, 1955). Figure 9 compares the rainfall intensity that occurred at gage 12-W with the intensity-duration-frequency relations developed for Dallas. The 500- year return-period curve was extrapolated, using techniques suggested by U.S. Weather Bureau (1961) in Technical Paper 40. An extrapolation to this great return period was done to show the relative intensity of the storm at 12-W. Figures 10, 11, and 12 compare the areal weighted rainfall intensity (the intensity that occurred over the entire watershed at the same time) over Bachman Branch, Joes Creek, and Turtle Creek, respectively, with the intensity-duration-frequency relation for Dallas. The return-period curves were drawn using point rainfall. A correction factor can be determined from the inset in figure 10 for each area. For example, to determine the return period for a 1-hour areal weighted-mean rainfall intensity on a 50-square-mile drainage area, divide the mean intensity by 0.80 and then enter the rainfall intensity-duration charts on the 60-minute line. Note that for Bachman Branch and Joes Creek the areal weighted rainfall inten: sity reached the 50-year return-period line. The figures show that the in uj 10 1 O :.95 I 4 O% ^ APRIL 1966 FIGURE 8. Accumulated rainfall, April 13-28, 1966, at rain gage

20 APRIL 28, 1966., NORTHERN PART OF DALLAS, TEXAS B15 intensity was rather constant for the first hour until it reached the maximum-return-period line, and then it followed this line for at least 1 hour. Figure 12 shows a decrease of the rainfall southward, but Turtle Creek experienced a record-breaking flood. The storm centered on the middle of White Eock Creek watershed. Plate 2 indicates the pattern of rainfall for the first 3 hours of the storm. The individual 30-minute totals are shown for each rain gage < D I o:2.0 LU 0. (/) LU f" (/) 5-4 t- 2 i < o: ^. ~-~, [^~~ ~- ^ -- x..^ ~- Ṉ -x. " " ^^ ^^ ^^ ^ L^^ <^J K~~-^ "\ "^ 1 ~-> \2 ^x^ K^_ ^~- K~~- x^- -^ ^ ^1 C^ "^ ^ <.; ^ \ itensity fo r Ap ril v t i ^> v. ^ \ ^\ \ X x X Note: Frequency analysis by method of extreme values, after Gumbel, k^/v 1941, for the period <^Q%j ^^ ^"x 1966 jf%^ " N ' $xn \ > N x 1v \ k N \ s NS \ s N N ^s ^ s,\ \ N\ \ N N N ^ \ \sx \ \\ N \ \ o Vs ^v\ \ MINUTES DURATION HOURS FIGTTKE 9. Comparison of maximum point rainfall intensity at gage 12-W with the rainfall intensity-duration-frequency curves for Dallas. The 500-year return-period curve was extrapolated, as suggested by U.S. Weather Bureau Technical Paper 40, and is shown for comparative purpose only.

21 B16 FLOODS OF 1966 IN THE UNITED STATES to indicate the amount of rain that accumulated at each site. Plate 2 also shows the total storm rainfall. Note that the storm traveled slowly downstream. Plate 2 (first 1 hour, 30 minutes) indicates, for example, that the peak intensity occurred at all rain gages north of Eoyal Lane and at none of the rain gages south of this road. This timing would logically increase the peak discharge-rainfall ratio and should account, in part, for the magnitude of the flood Note: Frequency analysis by method of extreme values, after Gumbel, 1941, for the period Intensity for April 28, Z 0.8 z.0.6 Z 0.4 < AREA, IN SQUARE MILES MINUTES HOURS DURATION Note: 10.0 square miles drainage area above Midway Road FIGURE 10. Comparison of rainfall intensities on Bachman Branch watershed with the rainfall intensity-duration-frequency curves for Dallas.

22 APRIL 28, 1966, NORTHERN PART OF DALLAS, TEXAS B Note: Frequency analysis by method of extreme values, after Gumbel, 1941, for the period oc D O I ^.0.6 X N \ ^\ Z0.4 <0.2 Intensity for April 28, MINUTES DURATION HOURS Note: 7.51 square miles drainage area above State highway 114 FIGTJBE 11. Comparison of rainfall intensities on Joes Creek watershed with the rainfall intensity-duration-frequency curves for Dallas.

23 B18 FLOODS OF 1966 IN THE UNITED STATES _ =»-~ ^^ ~ 5^ - U ^ ^ ^ "-- ^ "~» ^ ^. "- ^ ^ -- ^ -. [^ ~- ^^ -1 L^,^ ^ -^ ^ ^ ^^" <^ (^^ "^ tm -C^\ h?^ ^ ^ ^: ^ \ ;\ Note: Frequency analysis by method of extreme values, after Gumbel, 1941, for the period *? )(/^ ^\ ^Op^ %/Q X( ^ X ^^$xx X ^x/^ ^ \ *j X = ~ ~ ~ - ~ Inte nsity 1or April a, 1966 X * X^ F^ 1 X v > X s K\ V t \ s \ \x [\ X \^vx N vs ^s^ X N, N \ s^ N \\\ - \ x\^^ \ \ \ x> ^ X ^\ ~ n n? MINUTES HOURS DURATION Note: 7.98 square miles drainage area above Hall Street FIGUBE 12. Comparison of rainfall intensities on Turtle Creek watershed with the rainfall intensity-duration-frequency curves for Dallas.

24 APRIL 28, 1966,, NORTHERN PART OF DALLAS, TEXAS B19 The pattern and amount of rainfall resulted in a flood that exceeded historical floods. GENERAL DESCRIPTION OF THE APRIL 28, 1966, FLOOD The weighted-mean rainfall for Joes Creek watershed was 4.86 inches. A point total of 4.45 inches was measured on the upper end of the watershed, and 5.04 inches was measured on the lower end. Rain fell on the entire watershed within 5 minutes after the storm began. The maximum intensity for a 30-minute period was 3.74 inches per hour (fig. 11). Joes Creek at State Highway 114 had a peak discharge of 6,350 cfs. Eighty-five percent of the 4.86-inch rainfall on the 7.51-square-mile watershed above this site ran off. Figure 13 shows rainfall-runoff JOES CREEK AT STATE HIGHWAY 114 (Drainage area, 7.51 square miles) 10 i. i i i i 10 BACHMAN BRANCH AT MIDWAY ROAD (Drainage area, 10.0 square miles) 10 i. i i i i G 18 Z O Z < O CD D O 10 < en 8 D Oi i- 6 z A4 K TIME, IN HOURS Q EXPLANATION Discharge Accumulated rainfall Accumulated runoff minute-interval weighted rainfall TIME, IN HOURS FIGTJEE 13. Rainfall-runoff hydrographs for storm of April 28, 1966, on Creek and Bachman Branch watersheds. Joes

25 B20 FLOODS OF 1966 IN THE UNITED STATES graphs for the State Highway 114 site. Upstream at Walnut Hill Lane, the peak discharge was 6,530 cfs, or a unit runoff of 1,750 cfs per sq mi from 3.73 square miles. (See pi. 2 for flood-determination points.) Figure 2 shows the April 28 flood profile for Joes Creek, along with a profile of the October 8, 1962, flood. Note that above Merrell Eoad the 1966 flood was lower than the 1962 flood. This is due in part to new bridges and channel rectification. Other measurements of discharge show the April 28, 1966, flood to be equal to or greater than the October 8,1962, flood. Total rainfall measured on the Bachman Branch watershed was 5.30 inches in the upper part and 5.27 inches in the lower part. The influence of rainfall measurements at points outside the watershed lowered the weighted-mean rainfall for the watershed to 5.17 inches. Eain was falling on the entire watershed within 20 minutes. The maximum intensity for a 30-minute period was 3.86 inches per hour (fig. 10). ^ Peak discharge was determined at six sites in the watershed (pi. 2). The highest measured peak rate of runoff per square mile was 3,160 cfs on Slaughter Branch at Walnut Hill Lane from a drainage area of 1.51 square miles. Bachman Branch at Webbs Chapel Road, with a drainage area of 11.0 square miles, had a peak discharge of 18,200 cfs, or a unit discharge rate of 1,650 cfs per sq mi. Eighty-nine percent of the 5.17-inch rainfall on the 10.0 square mile watershed above Bachman Branch at Midway Eoad ran off. Figure 13 shows rainfallrunoff graphs for the Midway Eoad site. Figure 2 shows the April 28 flood profile for Bachman Branch along with a profile of the October 8, 1962, flood. Note that above Forest Lane the April 28, 1966, flood was lower. This is due to the new bridge at Willow Lane and the channel rectification in the area. Downstream discharge measurements indicate the 1966 flood to be greater than the 1962 flood. Weighted-mean rainfall on the Turtle Creek watershed was 3.53 inches. Point rainfall totals measured in the Turtle Creek watershed ranged from 2.49 inches on the lower end to 4.78 inches on the upper end. The maximum 30-minute intensity was 3.42 inches per hour (fig. 12). Eain fell on the entire watershed within 15 minutes after the rain began. The two storm sewers from Northwood Eoad to below Lovers Lane overflowed, and floodwaters ran down the streets. Peak discharge was determined at two sites in this watershed (pi. 2). The maximum measured unit rate of runoff was 2,090 cfs per sq mi at a dam 600 feet below McFarlin Boulevard; drainage area is 2.43 square miles. Ninetytwo percent of the 3.53-inch rainfall on the 7.98-square-mile watershed above Turtle Creek at Hall Street ran off. Figure 14 shows rainfall-

26 APRIL 28, 1966,, NORTHERN PART OF DALLAS, TEXAS B21 runoff graphs for the Hall Street site. Figure 4 shows the April 28 flood profile for Turtle Creek. Weighted-mean rainfall for the 125-square-mile area above White Eock Creek at Scyene Koad was 4.06 inches. Measured-point rainfall ranged from 2.59 inches on the upper end, to 6.70 inches near the center, to 2.20 inches on the lower end of the watershed. The maximum intensity was recorded and the highest total rainfall for this storm was measured in the White Eock Creek watershed at rain gage 12-W (fig. 9). Peak discharge was determined at 11 sites (pi. 2). The highest measured unit rate of runoff was 2,070 cfs per sq mi from the 8.50-square mile area above Cottonwood Creek at Forest Lane. An almost equal unit discharge of 2,060 cfs per sq mi was determined for the 4.17 square miles above Floyd Branch at Forest Lane. Seventy-six per- TURTLE CREEK AT HALL STREET (Drainage area, 7.98 square miles) 10 WHITE ROCK AT GREENVILLE AVENUE (Drainage area, 66.4 square miles) TIME, IN HOURS EXPLANATION - Discharge - Accumulated rainfall Accumulated runoff [] 30-minute-interval weighted rainfall TIME, IN HOURS 12 FIGURE 14. Rainfall-runoff hydrographs for storm of April 28, 1966, on Turtle Creek and White Bock Creek watersheds.

27 B22 FLOODS OF 196,6 IN THE UNITED STATES cent of the rainfall on the 29.4-square-mile area above White Eock Creek at Keller Springs Road ran off. Sixty-six percent of the rainfall on the 66.4-square-mile area above White Bock Creek at Greenville Avenue ran off. Figure 14 shows the rainfall-runoff graphs for the Greenville Avenue site. Figure 5 shows peak stages for White Rock Creek above Northwest Highway (Loop 12) as determined from the network of the creststage gages. These peak stages are compared with profiles of other floods. Profiles of the April 28 flood were determined for Cottonwood Creek and Floyd Branch and are shown in figures 6 and 7, respectively. INUNDATION Flood plains in five of the watersheds were investigated for inundation. Plate 1 shows the area inundated by Joes Creek, Bachman Branch, Turtle Creek, Cottonwood Creek, and Floyd Branch. The map used as a base for plate 1 was prepared in 1958 and, consequently, does not detail the development since that time. New areas have been urbanized; industrial plants have been built; freeways have been constructed ; bridges have been rebuilt; and channels have been rectified. These developments have resulted in filling of the natural flood plain, straightening of the channel, changes in road grade, and addition of impervious cover. Each of these factors influences the magnitude and mode of the peak discharge and the consequent inundation. Examples of the effect of urban development are shown in figures 2 and 3. Most of the upper Joes Creek channel had been rectified prior to April 28, 1966, and since October 8,1962. As a result the April 28, 1966, peak stages were considerably lower than the October 8, 1962, peak stages in the rectified sections (fig. 2), even though the peak discharges in 1966 were equal to or greater than those in The bridge at Willow Lane on Bachman Branch had been rebuilt and the channel rectified since the flood of October 8, Figure 3 indicates the results of the hydraulic improvement at Bachman Branch at Willow Lane. The April 28, 1966, peak was 2 feet lower than the October 8,1962, peak. There is some uncertainty as to the exact area inundated by overflow from the north end of Bachman Lake Dam. Reportedly, this overflow inundated the area as far north as the Northwest Highway. An investigation of this area showed that certain parts of it had been under water; however, this could have been due to sheet runoff from local rainfall.

28 APRIL 28, 1966, NORTHERN PART OF DALLAS, TEXAS B23 FLOOD DAMAGE At least seven persons died in Dallas as a direct result of the floodwaters. Early damage estimates in the city were $2,500,000; according to Col. Jack Fickessen, District Engineer, U.S. Army Corps of Engineers. Of this amount, $1,330,000 was damage along Bachman Branch, where homes and businesses were inundated. The flash flood swept over north Dallas in the early morning hours of April 28, 1966, inundating the low-lying areas and sweeping cars, furniture, small buildings, and other items along with it. At some constricting points the water washed out bridges or removed large parts of the channel banks. Engineers collecting field data 2-3 weeks later found items such as clothing, furniture, garden tools, small tool sheds, and books in the flood plains of the streams. The inundation of many luxurious homes caused especially high flood damage. Figures show some results of the flood. DETERMINATION OF FLOOD DISCHARGE The standard method used by the Geological Survey to determine discharge at a gaging station is to develop a stage-discharge relation from current-meter discharge measurements made at various stages FIGURE 15. Flood damage on Joes Creek at Walnut Hill Lane.

29 B24 FLOODS OF 1966 IN THE UNITED STATES and then to apply this relation to records of stage. The record of stage is generally obtained from a water-stage-recorder installation that provides a continuous graphic or punch-tape record of stage. The reliability of the stage-discharge relation depends upon how adequately the discharge measurements define the entire range in stage. Current-meter measurements at or near the time of peak discharge at the gaging stations were impossible to obtain because the flood of April 28, 1966, was of short duration and occurred during the night. Indirect determinations of peak discharge were made at sites shown on plate 1. These peak discharges were obtained by slope-area, contracted-opening, culvert, or other types of indirect discharge measurements. These indirect measurements are based on field surveys of highwater profiles, channel geometry, and hydraulic-structure geometry and are computed in accordance with established hydraulic principles. They are indirect only because the data were collected subsequent to the passage of the flood. SUMMARY 1. The floods of April 28,1966, were the result of a combination of the events and conditions, as follows: a. The rain fell at the same intensity for about 1 hour (figs. 9-12). The gage (12-W) that recorded 6.7 inches in 6 hours and 4.92 inches in a 1-hour period also recorded rainfall intensities for durations of 30 minutes-2 hours that exceeded a 100-year return period by a considerable amount (fig. 9). FIGURE 16. Flood damage on Bachman Branch. Peak marks can be seen on curtains. Photograph by Dallas Morning News.

30 APRIL 28, 1966, NORTHERN PART OF DALLAS, TEXAS B25 FIGUEE 17. Flood damage on Turtle Creek at Fitzhugh Avenue. Photograph by Dallas Morning News.

31 B26 FLOODS OF 1966 IN THE UNITED STATES FIGURE 18. Flooding on White Rock Creek at Scyene Road. Photograph by Dallas Morning News,

32 APRIL 28, 1966, NORTHERN PART OF DALLAS, TEXAS B27 b. Seven storms had occurred in the preceding 2 weeks, leaving the ground well saturated and the storage areas full. c. The watersheds are extensively urbanized and therefore contain a large amount of impervious cover. 2. Floods exceeded historical floods on Joes Creek, Bachman Branch, Turtle Creek, Cottonwood Creek, and Floyd Branch. (Flood history at some sites dates as far back as 1892.) 3. The second highest peak-runoff rate per square mile ever measured in Texas occurred on Slaughter Branch at Walnut Hill Eoad, where 4,770 cfs ran off from an area of 1.51 square miles (3,160 cfs per sq mi). This peak rate of runoff is second only to the 3,350 cfs per sq mi that occurred on Bunton Branch on June 30, 1936, from an area of 4.12 square miles. 4. A high percentage of the rainfall ran off each watershed. Joes Creek had 81 percent runoff, Bachman Branch had 89 percent, and Turtle Creek had 92 percent. STREAMFLOW DATA EXPLANATION OF DATA Maximum stages and discharges at the continuous-record gaging stations, crest-stage partial-record stations, and miscellaneous sites are summarized in table 1. The derivation of the maximum data is explained in the station descriptions for each site in the "Station Data" section of this report. The peak-discharge values given in table 1 are for flow as it passed the gaging station or measuring site. Under the heading "Maximum Flood Prior to April 28,1966," the maximum historical flood is given. Peak discharges, in cubic feet per second per square mile, were computed for all sites. Following table 1, additional data are presented for each station where streamflow information was collected by the Geological Survey during the April 28, 1966, flood. In general, the information for each continuous-record gaging station is as follows: A description of the station, and a tabulation of stages and discharges at selected times during the day of April 28,1966. For the miscellaneous sites and creststage partial-record stations, only the station description is presented, because no information other than maximum stages and discharges is available.

33 B28 FLOODS OF 1966 IN THE UNITED STATES TABLE 1. Flood stages and discharges, flood of April 28, 1966, in Dallas, Texas Map Permanent Stream and place No. station of determination (pi. 1) No. Drainage area (sqmi) Prior to April 28, 1966 Period Year Maximum floods April ] Elevation. Discharge 1966 (ft) Cfs per Cfs sq. mi. Joes Creek watershed Hill Lane. Joes Creek at State Highway i (2) 6,530 7,430 6,350 1, Bachman Branch watershed Bachman Branch at Walnut Hill Lane. Slaughter Branch at Walnut Hill Lane. Bachman Branch at Northwest Highway. Bachman Branch at Midway Road. Bachman Branch at Webbs Chapel Road. Bachman Branch at Bachman Lake ,160 10,400 4,770 8,530 14,400 9,200 16,000 18,200 15,000 1,300 2,200 3, , ,600 1,660 1,200 Turtle Creek watershed Turtle Creek below McFarlin Boulevard. Turtle Creek at Hall Street. o ,080 4,660 12,200 2, ,500 White Rock Creek watershed " White Rock Creek at Seller Springs Road. Spanky Branch at McCallum Lane Armstrong Branch at Melrose Avenue, Richardson, Tex. Cottonwood Creek at Forest Lane. Floyd Branch at Valley View Road. Floyd Branch at Forest Lane. White Rock Creek at Greenville Avenue. White Rock Creek at White Rock Lake. Ash Creek at Highland Drive. Forney Creek at Lawnview Avenue. White Rock Creek at Scyene Road ,900 9,020 7,870 5,000 1,290 (») 17,400 17,600 4,030 6,170 (») 8,590 38,100 27,000 28,300 18,800 «5,180 «1,090 "36,"206" 21,600 1, , ,220 2,050 2,070 1,270 1,940 2, """ Peak elevation not comparable with that of April 8,1966, because of subsequent channel rectification. 8 Not determined. 3 Affected by backwater from the Trinity River.

34 APRIL 28, 1966, NORTHERN PART OF DALLAS, TEXAS B29 The station description gives the following information: Location of the gage; size of drainage basin area above the gage; nature of the gage-height record obtained during the period discussed in this report; datum of the gage; definition of the stage-discharge relation; maximum stage and discharge during the April 28, 1966, flood; previous maximum during the period of station operation; and available maximum data for floods outside the period of station operation, as indicated from interviews with local residents and from reading historical documents. The tables of stage and discharge at selected times where such detailed definition is warranted are given after the station description. Enough detail is presented so that hydrographs for the flood period can be accurately constructed. STATION DATA JOES CREEK AT WALNUT HILL LANE, DALLAS, TEX. (Miscellaneous site) Location. Lat 32 52'50" N., long 96 51'38" W., at culvert on Walnut Hill Lane, Dallas, Dallas County, 2.6 miles upstream from Interstate Highway 35B. Drainage area sq mi. Elevation record. From floodmarks. Datum is mean sea level, datum of 1929, supplementary adjustment of Discharge record. Maximum discharge by computation of flow through culvert and over road. Maximums. April 28, 1966: Discharge, 6,530 cfs (elev, ft) to April 28, 1966: Elevation, ft Oct. 8, Remarks. Road at both ends of the bridge was raised and the channel rectified for about 2,000 ft downstream since the Oct. 8,1962 flood JOES CREEK AT STATE HIGHWAY 114, DALLAS, TEX. Location. Lat 32 51'33" N., long 96 53'00" W., at bridge on State Highway 114, 0.9 mile above mouth, 7.8 miles northeast of Dallas County Courthouse in Dallas. Drainage area sq mi. Elevation record. SR (stage-rainfall) recorder graph, outside peak marks, and outside staff-gage readings. Datum of gage is mean sea level, datum of 1929, supplementary adjustment of Discharge record. Stage-discharge relation defined by current-meter measurements below 730 cfs and by contracted-opening measurements at 3,300 and 6,350 cfs. Maximums April 28, 1966: Discharge, 6,350 cfs 0300 hours (elev, ft) to April 28, 1966: Discharge, 7,430 cfs Oct. 8, 1962 (elev, ft, from floodmarks). Since at least 1904: Discharge, that of Oct. 8,1962; elevation: 431 ft in 1908; backwater from Trinity River.

35 B30 FLOODS OF 1966 IN THE UNITED STATES [Elevation, in feet; discharge, in cubic feet per second; and accumulated runoff, in inches, at indicated time, April 28,1966] Hour Elevation Discharge Accumulated runoff Hour Elevation Discharge Accumulated runoff ,340 4,300 4,900 5,000 5,600 5,800 6,350 5,800 5,600 5,150 4, ,800 2,250 1,850 1,580 1,370 1,200 1, BACHMAN BRANCH AT WALNUT HILL LANE, DALLAS, TEX. (Miscellaneous site) Location. Lat 32 52'48" N., long 96 49'26" W., at bridge on Walnut Hill Lane, Dallas, Dallas County, 5.4 miles upstream from Interstate 35E. Drainage area sq mi. Elevation record. From floodmarks. Datum is mean sea level, datum of 1929, supplementary adjustment of Discharge record. Maximum discharge by contracted-opening measurement. Maximums. April 28,1966 : Discharge, 10,400 cfs (elev, ft) to April 28, 1966: Discharge, 6,160 cfs on Oct. 8, 1962 (elev, ft, from floodmarks). Remarks. Dam about 1,000 ft downstream from Walnut Hill Lane removed since Oct. 8, 1962 flood. SLAUGHTER BRANCH AT WALNUT HILL LANE, DALLAS, TEX. (Miscellaneous site) Location. Lat 32 52'48" N., long 96 49'03" W., at Culvert on Walnut Hill Lane, Dallas, Dallas County, 1.1 miles upstream from mouth. Drainage area sq mi. Elevation record. From floodmarks. Datum is mean sea level, datum of 1929, supplementary adjustment of Discharge record. Maximum discharge by computation of flow through culvert and flow over road. Maximum. April 28,1966: Discharge, 4,770 cfs (elev, ft). BACHMAN BRANCH AT NORTHWEST HIGHWAY, DALLAS, TEX. (Miscellaneous site) Location. Lat 32 51'48" N., Long 96 49'48" W., at culvert on Northwest Highway (Loop 12), Dallas, Dallas County. Drainage area sq mi. Elevation record. From floodmarks. Datum is mean sea level, datum of 1929, supplementary adjustment of Dioharge record. Maximum discharge by computation of flow through culvert and over road. Maximums. April 28,1966 : Discharge, 14,400 cfs (elev, ft) to April 28, 1966: Discharge, 8,530 cfs on Oct. 8, 1962 (elev, ft).

36 APRIL 28, 1966, NORTHERN PART OF DALLAS, TEXAS B BACHMAN BRANCH AT MIDWAY ROAD, DALLAS, TEX. Location. Lat 32 51'26" N., long 96 50'12" W., on right bank at downstream side of bridge on Midway Road at Dallas, Dallas County, 1,400 ft south of Northwest Highway, 1.5 miles upstream from Bachman Lake Dam, and 6.0 miles northwest of Dallas City Hall. Drainage area sq mi. Elevation record. Water-stage recorder graph to 0330 hours. Graph drawn on basis of floodmarks and wire-weight gage readings. Datum of gage is mean sea level, datum of 1929, supplementary adjustment of Discharge record. Stage-discharge relation defined by current-meter measurements below 4,000 cfs; by contracted-opening measurements of 5,300, 9,200, and 16,000 cfs. Maximums April 28, 1966: Discharge, 16,000 cfs 0410 hours (elev, ft, from floodmarks) to April 28, 1966: Discharge, 5,170 cfs May 10, 1965 (elev, ft). Since at least 1900: Discharge, 9,200 cfs Oct. 8, 1962 (elev, ft, from floodmarks). [Elevation, in feet; discharge, in cubic feet per second; and accumulated runoff, in inches, at indicated time, April 28,1966] Hour Elevation Discharge Accumulated runoff Hour Elevation Discharge Accumulated runoff ,700 5,410 13,100 16,000 12,800 6,680 2,490 1, BACHMAN BRANCH AT WEBBS CHAPEL ROAD, DALLAS, TEX. (Miscellaneous site) Location. Lat 32 51'33" N., long 96 51'21" W., at bridge on Webbs Chapel Road, Dallas, Dallas County. Drainage area sq mi. Elevation record. From floodmarks. Datum is mean sea level, datum of 1929, supplementary adjustment of Discharge record. Maximum discharge by contracted-opening measurement and computation of flow over road. Maximum. April 28, 1966: Discharge, 18,200 cfs (elev, ft). BACHMAN BRANCH AT BACHMAN LAKE, DALLAS, TEX. (Miscellaneous site) Location. Lat 32 50'55" N., long 96 52'16" W., at spillway of Bachman Lake, Dallas, Dallas County. Drainage area sq mi. Elevation record. From floodmarks. Datum is mean sea level, datum of 1929, supplementary adjustment of Discharge record. Maximum discharge by computation of flow over spillway and flow over embankment. Maximum. April 28,1966: Discharge, 15,000 cfs (elev, ft).

37 B32 FLOODS OF 1966 IN THE UNITED STATES TURTLE CREEK BELOW McFARLIN BOULEVARD, DALLAS, TEX. (Miscellaneous site) Location. Lat 32 50'35" N., long 96 47'54" W., at dam 600 ft downstream from McFarlin Boulevard, Dallas, Dallas County. Drainage area sq mi. Elevation record. From floodmarks. Datum is mean sea level, datum of 1929, supplementary adjustment of Discharge record. Maximum discharge determined by computation of flow over dam. Maximum. April 28,1966: Discharge, 5,080 cfs (elev, ft) TURTLE CREEK AT DALLAS, TEX. Location. Lat 32 48'26" N., long 96 48'08" W., on left bank 68 ft upstream from Hall Street at Dallas, Dallas County, and 2.0 miles north of Dallas County Courthouse. Drainage area sq mi. Elevation record. Water-stage recorder graph. Datum of gage is mean sea level, datum of 1929, supplementary adjustment of Discharge record. Stage-discharge relation defined by current-meter measurements below 2,500 cfs and by computation of flow over dam and flow over embankment at 12,200 cfs. Maximums. April 28, 1966: Discharge, 12,200 cfs 0410 hours (elev, ft) to April 28, 1966: Discharge, 4,650 cfs Oct. 1, 1959 (elev, ft). Since at least 1903: Discharge, that of April 28,1966. [Elevation, in feet; discharge, in cubic feet per second; and accumulated runoff, in inches, at indicated time, April 28,1966] Hour Elevation Discharge Accumulated runoff Hour Elevation Discharge Accumulated runoff ,880 4,130 6,160 10,400 12,200 11,200 7,900 4,850 3,750 2,690 1,550 1, , WHITE ROCK CREEK AT KELLER SPRINGS ROAD, DALLAS, TEX. Location. Lat 32 58'13" N., long 96 48'19" W., on left bank at downstream side of bridge on Keller Springs Road in Dallas, 0.5 mile upstream from St. Louis Southwestern Railway Lines bridge, 0.9 mile upstream from Spanky Branch, and 13 miles north of Dallas County Courthouse. Drainage area sq mi. Elevation record. Water-stage recorder graph. Datum of gage is mean sea level, datum of 1929, supplementary adjustment of 1953.