FLOOD04833

• Designation Number: 421
• County: Arapahoe
• County: Adams
• Community: Aurora
• Stream Name: Upper Box Elder Creek
• Basin: South Platte
• Title: Hydrology Report - Upper Box Elder Creek Outfall Systems Planning Study
• Date: 3/1/1994
• Prepared For: UDFCD
• Prepared By: CH2MHILL
• Floodplain - Doc Type: Floodplain Report/Masterplan

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I-
I
I

Section 3.0
Hydrologic Analysis

3.1 ~or Watersheds

The study area was divided into five major watersheds and modelled separately, to man-
age the size of the models. Watersheds 1 and 2 pertain to downstream and upstream
Coyote Run. Watersheds 3, 4, and 5 pertain to lower, middle, and upper Box Elder
Creek within the study area. In addition, the watershed upstream of the study area was
modelled in order to provide representative inflow hydrographs at the upstream study
limit. This upstream watershed was designated as Watershed 6. The Watershed 6
analysis w~ conducted with less detail than the analysis of the five watersheds within the
study area.

3.2 Subwatersheds

Each of the five watersheds in the study area were divided into subwatersheds as shown
in Appendix E. The subwatersheds were numbered consecutively from north to south
and limited to a maximum area of 130 acres. Watershed 6 (upstream of the study area)
was divided into subwatersheds with areas no greater than 10 square miles. A work map
of Watershed 6 is shown in Appendix F. As shown in Table 3-1, the study area was
divided into a total of 615 subwatersheds with an average area of 78 acres and Water-
shed 6 was divided into 18 subwatersheds with an average area of 7 square miles.

I Table 3-1 I
Subwatershed Distribution
Watershed Number Number of Sub watersheds
1 94
2 136
3 98
4 156
5 131
Subtotal 615
Watershed Area (square miles) 75
Average Subwatershed Area (acres) 78
6 18
Watershed Area (square miles) 127
Average Subwatershed Area (square miles) 7
I Total Number of Subwatersheds I 633 I

DENlOOISI86.WP5

3-1