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<br />which IS similar to values used In other studies performed by the USBR for the front range drainages
<br />in Colorado, a theoretical lag time of 3,2 h was calculated. The Buckhorn DUH developed for a
<br />similar basin In the northern foothills of Colorado was adopted.
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<br />PMP for this study was developed from the recently established criteria ,n HMR 55 [2], which
<br />covers the region from the 1 03d meridian to the Continental Divide. The PMP for this study totaled
<br />34,58 in of rain in 72 h, The maximum 4.h total PMP is 21.38 in, which compares with the 14
<br />inches in 4 h recorded in a nearby basin,
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<br />No flood volume information is available for the observed event. Loss rates for the PMF devel-
<br />opment were assumed to be 0,2 in (initial) and 02 in/h (constant), These loss rates are equivalent
<br />to other USBR PMF study loss rates in the front range of Colorado.
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<br />The PMF computed on the basis of data and assumptions described has a peak of 1 91 ,000
<br />ft3/S, The observed peak of 124,000 ft3/s is equivalent to 65 percent of the estimated PMF peak
<br />value. Plate 4 shows a comparison of the computed PMF and the historic peak flood for this site.
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<br />4. Seco Creek near D'Hanis, Texas
<br />
<br />Seco Creek has its headwaters in Bandera County, Texas, at an elevation of about 2000 ft, The
<br />creek flows southeastward across Medina and FriO Counties. The creek crosses the Balcones fault
<br />zone 3 few miles above D'Hanis, The drainage area above the fault zone is hilly and sparsely
<br />wooded. It is used mainly for ranching,
<br />
<br />In the early morning of May 31, 1935. a heavy rainfall over the Seco drainage basin above O'Hanis
<br />in the early morning of May 31, 1935, caused the creek to rise rapidly and reach stages much
<br />higher than ever previously recorded, In the town of O'Hanis, water reached a maximum stage
<br />about 10:00 a,m, after having risen rapidly for several hours. About 6 mi above D'Hanis, Seco
<br />Creek overflowed and merged with the floodwaters from Parker Creek. 80th Seco and Parker
<br />Creek had broken out along new courses, Near their banks many homes that had never before
<br />been in danger from previous floods, were flooded
<br />
<br />There were no official rainfall stations anywhere in the Seco Creek drainage. Very little reliable
<br />information was available for the precipitation that caused this flood, All receptacles ordinarily
<br />used for measuring outstanding rainfall were reported to have run over or were washed away,
<br />The best information reported was from ,he Woodward Ranch, approximately 17 mi by road
<br />above O'Hanis, The ranch manager reported that 22 to 24 in of rain fell in 3 Y2 h, from 1:45 to
<br />5: 15 a.m, on May 31. This information was based on measurements of the rain that fell into a
<br />masonry trough and into a large paint can, Other ranches reported different amounts, ranging from
<br />16 in approximately 5 mi west of the Woodward Ranch to 6,5 in approximately 6 mi north, The
<br />closest official weather stations were at Sao,nal. 3oproximately 12 m, west of O'Hanls, and at
<br />Hondo, approximately 9 mi east, These stations reported 7,70 and 9,15 In, respectively, for the
<br />6-h period from 5:00 to 1100 am on\ilav 31 ; 2' i
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