FLOOD07093

• County: Otero
• County: Pueblo
• Community: Otero, Pueblo Counties
• Stream Name: Arkansas River
• Basin: Arkansas
• Title: Arkansas River Channel Capacity and Riparian Habitat Planning Study
• Date: 8/1/2001
• Prepared For: CWCB
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Project

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After further discussion with the experts at BEC and due to the fact that the stream gages
had different period of records, we decided that further smoothing and interpolation of the data
was necessary to develop reasonable results. Therefore, the hydrologic analysis supported
completely by frequency-discharge relationships computed for the individual gages proved very
reasonable with the added peak flow values of 1921. It is recommended that the results
presented in Table 3.2 above be used as the peak frequencies of flows at these stream gage
locations based on data through 1999.

3.2.2 Historic Sediment Information

Relatively long-term records of discharge-suspended sediment exist for the Arkansas
River at Las Animas gage station. The period of record for this Arkansas River location is from
October 1942 to March 1972.

Logarithm (base 10) regression analysis was performed for the Arkansas River at Las Animas.
Figure 4 shows the scatter data and linear relation for the entire data set. The analysis consisted
of entering the values into a spreadsheet program, performing unit conversions to arrive at water
discharge in cubic feet per second (cfs) and suspended sediment discharge in tons per day (t1d),
elimination of zero discharges, sorting, and finally, correlation analyses of the logs of the water
versus the suspended sediment discharges. These analyses were recalculated using months rather
than days. Table 3-3 provides information on the success of the mathematical representations.

Table 3-3. Correlation (R2 values) of discharge versus suspended sediment.

Time Period

Arkansas River at Las
Animas, CO
0.85
0.86
0.92
0.75
0.88
0.90
0.77
0.81
0.65
0.90
0.94
0.95
0.85

January
February
March
April
May
June
July
August
September
October
November
December
Aggregate

The aggregate data and linear representations are relatively well behaved (smooth curves)
and consistent for the Arkansas River at Las Animas. The correlation coefficient for the
Arkansas River at Las Animas was 0.85. For the monthly analyses, the Arkansas River at Las
Animas shows reasonable curve fits, with correlation coefficients of 0.65 to 0.95.

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