FLOOD10395

• County: Larimer
• Community: Wellington
• Stream Name: Boxelder Creek
• Basin: South Platte
• Title: Floodplain Management Study - Boxelder Creek in the Vicinity of the town of Wellington in Larimer County - Supplement No. 1 to the Plan of Work
• Date: 3/1/1982
• Floodplain - Doc Type: Floodplain Report/Masterplan

ce

(e

(Ie

14

of values selected. Storage discharge curves for ponding behind channel
crossings were defined from topographic mapping and weir flow equations. The
ponded areas along Cooper Slough were upstream of the crossings at State
Highway 14, Colorado and Southern Railroad and Vine Drive. The ponded areas
along Boxelder Creek were upstream of 1-2S near Fort Collins and Wellington,
State Highway 14, abandoned Colorado and Southern Railroad, Vine Drive,
Larimer-Weld Canal and Willox Lane.
Table 7 lists a summary of infiltration and rainfall depths for the
100-year rainfall events. Infiltration depths are approximately one inch.
Tables 8 and 9 list the storage discharge curves used in the SWMM analysis for
Cooper Slough and Boxelder Creek, respectively.

~-'"

2.3 Results
Rainfall-runoff data were not available for the Cooper Slough or Boxelder
Creek basins. For this reason, the results of the Fossil Creek and Dry Creek
studies were used to evaluate and justify the results of this study. The peak
discharges per square mile from Dry Creek and Cooper Slough are very similar.
Figure 4a shows the peak discharge in cfs per square mile for the 100-year
recurrence interval storm event from the regional studies. The Fossil Creek
basin produces higher peak flows per square mile because of steeper slopes and
lower infiltration rates than the Boxelder Creek and Cooper Slough basins.
The Boxelder Creek drainage basin is longer and flatter than Dry Creek and has
lower unit area peak discharges. Also, soils in the Boxelder Creek basin are
more permeable than the soils in the Fossil Creek basin.
A summary of the peak flows for existing and developed conditions in the
Cooper Slough basin is given in Table 10. A summary of peak flows for the
combined Boxelder Creek-Cooper Slough basins is given in Table 11. The
discharge profiles which show the change in flow rate along the study reach
for Boxelder Creek are given in Figure S. Figures 6 and 7 present the
discharge profiles for Cooper Slough for existing and developed conditions,
respectively. The flood hydrographs at three locations within each basin are
given in Figures 8, 9 and 10 for Boxelder Creek, Figures 11, 12 and 13 for
Cooper Slough with existing basin conditions, and Figures 14, 15, and 16 for
Cooper Slough with developed basin conditions.