|
<br />32 FLOODS OF SEPT. 1970 IN ARIZ., UTAH, COLO., AND N. MEX.
<br />
<br />broad flat area east and south of Pinon, and a tributary flows through a
<br />similar area on the west side of Piilon. Both streams overflowed their banks
<br />and inundated large areas on three sides of the community.. The floodwater
<br />covered areas 3/4 mi (1.2 km) wide in the broad flats alDng Wepo Wash and
<br />about 112 mi (0.8 km) wide along the tributary. Downstream from Pinon,
<br />the flow from Wepo Wash removed sections of Reservation Highway 3 and
<br />damaged several earthen dams west of Polacca. The peak flow of Dinnebito
<br />Wash near Oraibi (fig. 11, No. 72) was 28,900 flJ/s (818 m'/s) from a
<br />drainage area of 261 mi' (676 km'). The flow of Oraibi Wash at the road
<br />crossing north of Pinon was of about the same magnitude as that measured
<br />in Dinnebito Wash; the drainage area of Oraibi Wash at the road crossing is
<br />213 mi' (552 km').
<br />
<br />FOUR CORNERS AREA
<br />
<br />I
<br />
<br />..
<br />
<br />
<br />,~.
<br />
<br />",
<br />
<br />,t
<br />
<br />!
<br />!
<br />.
<br />
<br />Ho...T_'-
<br />
<br />FOUR CORNERS AREA
<br />
<br />FLOOD OF SEPTEMBER 5.7. 1970
<br />
<br />Large amounts of rain in the San Juan Mountains in southwestern
<br />Colorado and along the Utah-Colorado State line caused flooding in the
<br />Dolores River and San Juan River basins during September 5-7 (fig. 12).
<br />The flood was not as large as that of October 1911, which is the largest
<br />known flood in the area. The 1911 flood peaks were not only of greater
<br />magnitude but were of longer duration. Although some high flows occurred
<br />in the upper .reaches of the Rio Grande basin on the east slopes of the San
<br />Juan Mountains, the flows were not of unusual magnitudes.
<br />
<br />..If 1.1'
<br />
<br />n.
<br />
<br />i
<br />'. I'
<br />""1--..,
<br />.'-'-' \!
<br />
<br />,,~LL"
<br />
<br />".
<br />
<br />R'.~~
<br />
<br />':'''''''''''
<br />
<br />EXPLAN...T10N
<br />If'STREAMfLOW-G...Q'NGSTATION-.....-..,....__
<br />"'ma,,,,_&.""i~.,,,,;o.,,dGo
<br />~ ...'ICELL.....EOUSSTREAMFLOW....tMu"'NGSITE-
<br />N_~"''''',i''_&.nd;.,...tlon'''''
<br />
<br />DOLORES RIVER BASIN
<br />
<br />In the Dolores River basin in Colorado the flood of 1970 was considerably
<br />smaller than that of 1 9 1 1, and flood damages were minor except in a few
<br />places. The U.S. Army Corps of Engineers (1970) reported that roads,
<br />bridges, irrigation facilities, and farmland were damaged near Rico and
<br />Dolores and along Disappointment Creek..The community water supply for
<br />Dove Creek was cut off when high flows in Big Canyon Creek-a small
<br />tributary of the Dolores River-washed out large sections of the waterline
<br />between Dove Creek and the Dolores River. At Naturita, the water-supply
<br />system was damaged by the flood in the San Miguel River. Large flows in
<br />Dry and Tabeguache Creeks, tributaries to the San Miguel River above
<br />Vravan, contributed to the flooding at Vravan, where levees and several
<br />homes were damaged.
<br />
<br />.~.
<br />
<br />lO<U:"'ffiR'1
<br />
<br />......p"".."Jl....OLC)Q.C..LSU..V.y
<br />....'zO........I05.COLO"...DO........
<br />..EW....XI(:O.._,A.N(lUT...','..................
<br />
<br />FIGURE 12.-Location of ilood-determination sites in the Four Corners area.
<br />
<br />SAN JUAN RIVER BASIN
<br />
<br />Floods that greatly exceed the annual peak discharge from snowmelt are
<br />rare events in the upper part of the San Juan River basin. Two such floods
<br />have occurred since the early 1880's; the first was in September 1909, and the
<br />second was in October 1911. Although actual peak discharges for the flood
<br />of 1909 are unknown, precipitation records and newspaper accounts
<br />
<br />indicate that it was a major flood. In June 1927 a third large flood occurn
<br />as a result of rain on melting snow (Follansbee and Sawyer, 1948, p. 133
<br />At the gaging station on the San Juan River at Pagosa Springs, Colo. (fi
<br />12, No. 18), the peak discharge for the flood of 1911 was 25,000 ft'ls (7;
<br />m'/s), the peak for the flood of 1927 was 16,000 fP/s (450 m'/s), and tl
<br />peak for the flood of September 6, 1970, was 6,580 ft'l s (l86m'/s). The pe'
<br />on September 6 is the largest since at least 1935 but is only slightly larger th,
<br />the largest peak caused by snowmelt during the same period. At the gagi!
<br />stations on the Rio Blanco near Pagosa Springs, Colo., and the Piedra Riv
<br />near Piedra, Colo., the peak discharges of September 6 were the largest sin,
<br />records began in 1935 and 1938, respectively. Secondary roads, irrigatic
<br />facilities, and farmlands were damaged along the streams. Upstream fro
<br />Val.lecito Reservoir along Vallecito.Creek and its tributaries, sever
<br />vacation homes were destroyed or damaged. A longtime resident stated th
<br />the flood of 1970 was no greater than the flood in the summer of 195
<br />
|