_REVISION - M1981302 ‎(117)‎

• Permit No: M1981302
• IBM Index Class Name: Revision
• Doc Name: FLOOD HAZARD AREA DELINEATION SOUTH BOULDER CREEK JULY 1986
• Type & Sequence: AM2
• Media Type: D
• Archive: No

Study Area - FLOOD HISTORY -
The proposed 8.4 mile study reach for this project extends from the Colorado and Floods in the South Boulder Creek basin are produced by periods of intense
Southern Railroad (C&S R.R.) crossing, located approximately 1 .2 miles above the rainfall associated with either local or general storm systems. Typically, the
confluence with Boulder Creek, to the community of Eldorado Springs. thunderstorm systems which produce intense periods of rainfall occur during the
spring and early summer months, frequently augmenting runoff from snowmelt.
Existing development along the drainageway varies substantially throughout the
study reach. In the lower reaches, between the C&S Railroad crossing and The U.S.G.S. has maintained a stream gaging station on South Boulder Creek near
Arapahoe Road, the land west of the stream channel has been developed for Eldorado Springs since 1888, however, there have been lapses in its operation.
commercial and industrial uses. Land east of the channel to the Boulder Feeder The gage was not in operation from October 1892 to May 1895 , and from September
Canal is undeveloped. Upstream of Arapahoe Road, the areas adjacent to the 1901 to August 1904. It should be noted that a major flood event occurred on May
drainageway contain numerous residential structures along with an existing golf 29, 1894 during the period in which records were not kept. Table 2 presents
course. occurrences of peak discharges in excess of 1000 cfs that have been recorded at
this gaging station (Reference 2).
From Baseline Road upstream to State Highway 93, land use is predominantly
rural-agricultural . Numerous irrigation diversion structures are located along TABLE 2
t Historic Peak Discharges On
his portion of the creek.
South Boulder Creek at Gagingl
Station Near Eldorado Springs
Above the Denver-Boulder Turnpike (U.S. Highway 36) the topography abutting the Drainage Area: 109 Square Miles
southeast side of the creek is steep , rising fairly rapidly , whereas the Location: 6.7 miles downstream from Gross Reservoir
' northwest overbank areas are quite flat. Gravel mining activity is occurring and 1 mile west of Eldorado Springs
northwest of the creek above the Denver-Boulder Turnpike. A cluster of Peak Discharges2
' residential dwellings exist near the creek between State Highway 170 (Marshall Date of Occurrence c.f.s.
Road) and State Highway 93 (South Broadway). A mobile home park is located along 3 Jun 1895 1 ,130
the south bank of South Boulder Creek just upstream of State Highway 93. 9 May 190 1 , 0
20 Jun 1909 1 ,34340
24 May 1914 1,240
Above State Highway 93 the basin and floodplain become narrower and valley 6 Jun 19 , 0
2 Sep 1938 7 ,39
0
sideslopes rise more abruptly . The land use is still primarily 21 Jun 1947 1 ,290
rural-agricultural and is characterized by open pastureland in the valley bottom 6 Jun 19 , 0
18 Jun 1951 51 2,37370
and low growing brush on the valley slopes. 4 Jun 1952 1 ,080
7 May 1969 1 ,690
The community of Eldorado Springs is located at the upper end of the study 1 Records taken from United States Department of Interior Geological Survey,
reach. This community lies in bottom of the narrow, steep-walled mountain "Water-Supply Papers 1310 and 1680" and the yearly "Water Surface Records
for Colorado" .
canyon. Numerous residential structures have been built along the edge of the
2 Only peak discharges which exceeded 1 ,000 cubic feet per second (cfs) are
creek. listed.
' 4