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,---~- D30 FLOODS OF 1965 IN THE UNITED STATES was extensive. Highways were blocked by slides, irrigation systems sustained heavy damage, and many diversion dams were destroyed. The U .S, Bureau of Reclamation (oral commun., 1966) estimated damage in the Vermejo Conservancy District at $593,000 and damage in the Antelope Valley Irrigation District at $194,000. In Mora County, irrigation systems suffered $106,000 in damage, and in Colfax County 25 bridges and culverts were destroyed, All but two bridges over the Canadian River upstream from Conchas Dam were destroyed, The U,S. Army Corps of Engineers (1966) estimated damage of about $4 million in the Canadian River basin above Conchas Dam, Major damage occurred in the towns of Cimarron, Raton, and Springer. The U .S, Army Corps of Engineers (1966, table 7) estimated that about 330,000 acres of rural, urban, waste, and wooded lands were flooded in the tristate area. Over two-thirds of the inundated areas were between John Martin Dam, Colo" and Great Bend, Kans.; 55,000 acres were in the Cana- dian River basin in New Mexico, and the remaining 45,000 acres were along the Arkansas River and its tributaries above John Martin Reservoir, One disastrous result of cropland flooding is the deposition of sediment. For example, almost 2,000 acres in an area along Clay Creek were covered by several feet of silt and sand; also, on the Cain Ranch upstream from Two Buttes Reservoir, south of Lamar, Colo" deposition of sand and cottonwood-tree debris covered hundreds of acres and rendered the land useless for most practical purposes. Flood damage is always assessed in dollar amounts following disastrous floods, but the dollar figures reflect only a part ofthe true costs of man's ef- forts in cleanup activities. Who can determine, for example, what additional millions of dollars are spent in pure "shovel work," removing the muck and mire accumulated in homes, commercial buildings, and other es- tablishments? The assessed $60 million loss may be only one-half of the true cost resulting from the Arkansas River floods of 1965. FLOOD FREQUENCY The flood-frequency report (Patterson, 1964) contains curves for two regions and seven hydrologic areas that cover the 1965 flood area and also frequency curves for the main stems of the Arkansas and Canadian Rivers. The flood-frequency relations are limited because they are defined only to a recurrence interval of 50 years. Also, relations for small areas are not defined for any recurrence interval because of insufficient data on peak flows. Throughout the flood area the 1965 peak flows exceeded the 50-year flood by as much as 30 times. The true frequency of most of these peak flows cannot be determined from the present records, which are relatively short, In the Arkansas River basin, peak flows exceeded the 50-year flood by 30 times on Jimmv Camn and Clav Creek!il.. ltl timf";1<, on Rnlp. ~nrl Two Rnttp: 1 1 ~ ,