FLOOD07296

• Designation Number: 569
• County: Mesa
• Community: Grand Junction
• Stream Name: Bosley Wash
• Basin: Colorado Mainstem
• Title: Bosley Wash Drainage Master Plan - Phase 1: Watershed Floodplain Delineation
• Date: 11/1/2002
• Prepared For: Bosley Wash Watershed
• Prepared By: GMS
• Floodplain - Doc Type: Floodplain Report/Masterplan

i.

I:
.
.
.
.
.
.
.
.
.
.
.
i.
~.
.
.
.
.
i.
,
'.
.
.
i.
.
.
.
:.
.
.
.
!.
.
.
.
I.
I.
.
.
.
.
.
.
.

Bosley Wash Drainage Master Plan Phase I: Watershed Floodplain Delineation
I ~-m.~~~~~a,~;;.~i!l)~,:,'~lt;;'!';l,;,,:ii'ti,h;i,

For hydrologic routing elements along poorly defined channels or grassy swales, the Lag Method
was used, In this method, the travel time is calculated using the shallow concentrated flow
values, as described above, The upstream hydrograph is then translated downstream and lagged
by the travel time,

4.3 Curve Number Development

The SCS Curve Number method was selected to represent rainfall losses, The SCS Curve
Number is a function of hydrologic soil type, ranging from Type A (very well-drained) to Type
D (very poorly-drained), land use and cover, Most of the upper basin was classified by the
Natural resources Conservation Service (NRCS) as "badlands", and given a soil classification of
D (USDA, 2001), Soil types found in the lower basin ranged from B to D, The land use for the
upper basin was classified rangeland, with minimal herbaceous cover, poor hydrologic condition,
antecedent moisture condition II (average), with a resulting curve number of 89, Land uses for
the lower basin were determined based on GIS mapping and was composed of residential,
orchard, and grassland land uses, Table 4 presents the percentage of each land use along with the
resulting curve numbers,
,

.-

-""'-'~\Willnr~;;",~,l,o:

~

lil"1

.~~

/;"~..:r.f~'7,,
') ~.'
p - '\
"'f~,~~(;\.,!,;:\".

~.'
~

Page 13