FLOOD09702

• County: Adams
• Community: Broomfield, Westminster
• Basin: South Platte
• Title: Major Drainageway Planning
• Date: 11/1/1979
• Prepared For: Broomfield, Westminster
• Prepared By: UDFCD
• Contract/PO #: &&
• Floodplain - Doc Type: Floodplain Report/Masterplan

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SECTION I I
BASIN DESCRIPTION

TABLE II-I
GENERAL BASIN DATA
DIRECT FLOW AREA 3207
Basin
Subbasin Area Percent Average Slope
Number (Acres) Impervious* (ft,/ft. )
1 32 40 .019
2 107 40 .032
3 56 40 .026
4 53 42 .028
5 40 42 ,028
6 41 60 ,031
7 49 40 .035
8 67 20 .021
9 62 5 .044
10 47 40 .013
11 83 40 :.015
12 22 45 .017
13 64 20 .019
14 52 40 ,012
15 27 40 .029
16 37 40 .030
17 44 40 .014
18 23 40 .011
19 73 40 .008
20 25 40 .011
21 42 40 .019
22 114 40 .020
23 102 40 .020
24 82 40 .017
25 51 40 .026
26 15 30 .009
27 20 40 ,010
28 71 40 .010
29 57 40 .009
41 72 40 .029
42 29 5 .010
1,659
*Based on Future Developmett

The Direct Flow Area 3207 drainage basin is located within the cities of
Broomfield and Westminster in Township 1 South, Range 68 and 69 West of the
6th P,M, The basin has been divided into 31 subbasins and 7 channel reaches
for the purpose of this study, as shown on Figures II-I and 11-2. General
basin information is summarized in Table II-I. The basin is described in
detail on a reach basis below.

REACH I (Upper Limit of Study to Main Street)
The basin area tributary to Reach 1 is dominated by single-family residential
development, with the exception of the high school adjacent to Main Street
and south of Miramonte Boulevard. Development upstream from Miramonte Boule-
vard has been well pl anned wi th respect to drai nage and represents a fi ne
example of multipurpose use in the floodplain area, The subdivision open
space is located along the major drainageway and includes playgrounds and
bike paths. The cover illustration shows Miramonte Park, located just up-
stream of Daphne Street, There is no definite low flow channel in Reach 1,
except between Mi ramonte Boul evard and Mai n Street where the channel makes
two abrupt gO-degree bends. Major flows breach this channel and flow across
the high school baseball diamond.

The culverts at Daphne Street and Miramonte Boulevard allow 100-year flows to
overtop the roadway surface, however the depth of flow at both 1 ocati ons is
within the UD&FCD criteria for cross street flow, The existing 30-inch CMP
at Main Street is hydraulically inadequate for both the 2-year and 100-year
flows.

The Ridgeview Heights subdivision is currently under construction in the
undeveloped upper portion of Reach 1, and construction plans indicate that an
onsite detention facility has been designed to control excess runoff from the
single-family development.

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