FLOOD06987

• County: Arapahoe
• Community: Littleton
• Stream Name: South Platte River
• Basin: South Platte
• Title: Floodway Analysis Report River Front Place Development
• Date: 4/1/1983
• Prepared For: Littleton
• Prepared By: Resource Consultants
• Floodplain - Doc Type: Floodplain Report/Masterplan

South Platte River in this area. When the river is channelized. as is cur-

rently planned, the flood-plain water-surface elevations will be approxi-

mately 5 feet lower than the present flood-plain elevations and the major

part of the River Front Place property will be developable due to a change

in floodway mapping, as discussed above. Until these planned flood control

improvements for the South Platte River are in place, the current Flood

Insurance Study and flood-hazard mapping control the development of the

property. A more detailed hydraulic analysis was completed in order to

verify the results of the Flood Insurance Study.

FLOOD-PLAIN ANALYSIS

After careful review of the FIA Flood Insurance Study for this area,

it was determined that sufficient data had not been utilized within this

reach of the river to adequately determine the floodway limits. Therefore

a more detailed analysis was completed to determine the exact locations of

the floodway limits. This more detailed analysis indicates that additional

property can be developed, assuming approval of revised floodway limits can

be obtained.

Fig. 1 shows the location of the River Front Place property and also

shows the existing flood plain as well as the flood plain and floodway

calculated in the more detailed studies by Resource Consultants, Inc. The

revised floodway information resulted from using additional cross-section

information obtained through aerial mapping completed in March 1983. The

locations of these additional cross sections are shown on Fig. 1. The

cross sections are plotted in Figures 2 through 10.

There were two major changes in the hydraulic analysis completed by

Resource Consultants, Inc., as compared with the published FIA data. The

first difference was the 100-year flood discharge. In the Resource Consul-

tants, Inc., analysis, a discharge of 12,500 cfs was used. A review of the

computer output from the FIA study indicated'that the flood-plain hydraulics

were computed using 17,400 cfs for the 100-year discharge. There' appears

to be some discrepancy in the FIA study, and discussions with the Army

Corps of Engineers and Urban Drainage and Flood Control District indicates

3

RE:)OURCE: CON)ULTt\NT) INC