FLOOD10386

• County: Jefferson
• Community: Golden, Lakewood
• Stream Name: Upper Lena Gulch
• Basin: South Platte
• Title: FHAD - Upper Lena Gulch
• Date: 1/1/1993
• Prepared For: UDFCD
• Prepared By: Boyle Engineering Corporation
• Floodplain - Doc Type: Floodplain Report/Masterplan

IV. HYDRAULIC ANALYSIS

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The floodway has been computed for the

tabulated

the analyses for other recurrence Intervals

100-year event

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based on a one foot and a one-half foot rise in the energy grade line elevation

General

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Mapping

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Apex

Lena Gulch

floodway have been delineated along Upper

100-year floodplain and

The

The

mapping

base

for

interval

contour

mapping with a 2-foot

mapping coverage extended

=100

1

UDFCD provided

floodway

floodplain and

100-year

the

of

imits

The

View Tributary

Gulch and Pleasant

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located immediately

Maple Grove Reservoir,

20th Avenue, upstream along Lena Gulch

of

the Inlet

from

downstream of

levels

increases In water

regulated to prevent

is often

represent the area in which development

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Mapping was also

4.2 miles

for

Apex Gulch and Pleasant

for

provided

the Federal

Federal and state agencies such as

flood

and increased damages during a

confluences with Lena Gulch

their

from

View Tributary

Conservation Board (CWCB)

the COlorado Water

Agency (FEMA)

Emergency Management

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Mapping was performed by

1991

4

nc. based on aerial photography taken on Apri

respectively

miles

approximately 0.5 and 0.7

Landmark Mapping

for

upstream

the local municipalities

(UDFCD) as well as

the Urban Drainage and Flood Control District

and

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floodway delineations as a

floodplain and

the

of Jefferson County, Lakewood and Golden use

to oversee

flooding and

from

to damage

to identify areas particularly prone

mechanism

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the hydraulic analysis

use in

for

were provided

Approximately 200 digitized cross-sections

development activities in these floodplains

Cross-sections

time of the aerial photography

represent the basin conditions at the

These

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Cross-

the selected hydraulic model

into

input

for

format suitable

were provided in a digital

Hvdrology

the cross

View Tributary and 2

third decimal place in

representing Pleasant

A

to drainageway stationing

1

tributary sections with

section numbering corresponds

ndicates

section number

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representing Apex Gulch

which has been

the hydrology

floodway delineation is

floodplain and

this

for

The basis

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basin

fu

delineation assumes

The

report

this

of

section

summarized in an earlier

the affected communities

based on land use and zoning projections provided by

development,

I

the modeling of

in

to assist

were also provided by UDFCD

Supplemental structure surveys

and existing channel conditions

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Elevations

features were identified and provided

field surveys were conducted during May of 1991

physical

structure openings and other

These

drainageway crossings

measurements of

use In the analyses

for

which were

results of

the

discharge

100-year

A hydraulic analysis has been performed for the

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10-year,

Analyses were also performed for the

100-year floodplain and profile

used to plot the

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10

results of

the

O-year flood profile has been plotted and

The

50-year and 500-year discharges

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