FLOOD09717

• County: Boulder
• Community: Longmont
• Stream Name: St. Vrain Creek
• Basin: South Platte
• Title: Floodplain Information Report
• Date: 4/1/1981
• Prepared For: Longmont, Boulder County
• Prepared By: WRC Engineering, Inc.
• Contract/PO #: &&
• Floodplain - Doc Type: Floodplain Report/Masterplan

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CHAPTER [
INTRODUCTION

Therefore, upon official approval of this report by the Colorado
Water Conservation Board, the areas described as being within the
lOO-year flood (1% ohance Elood)* can be designated as flood ha.ard
areas and their use regulated accordingly by the local agencies.

A. Authorization

This study was authorized by the City of Longmone in cooperation ~ith
Boulder County and the Colorado Water Cot\servation Board. Specific tasks
were performed according to the terms of the contract dated February 15,
1979, between Colorado Water Con.ervation Board and Water Resources
Consultants, Inc.

B. Purpose and Scope

" . . . to utabfuh, lr.egu..tM:e., -\uu-ic.t, wui t.imU ~h
lUlU 01\ Oft a.{0I1.9 anI! 4tOJ!m M ~loodw:t.tVt ItWloH channl!J. 0"-
bWI1., .u m.ch ~ta.tm o.t ~t:OO~eA .tl.moH chanl1.e.t 1M bM.(>t
hM beendwg>>.a.ted <lild a"pilovedblJtite CO.tMwlOWa.tu Con-
~eAva.t.i.on Bo<V!d,.(/'I o.tdvt Ui .te.uen M avo.(d .the hazWld.. to
pM.60M <tiId d~e t.o (VlOpMh) "e..w.U,mg 6!(Gm till!. ac.cumu.la-
tiCI'! Ot ~to.tm OJ!. 6ioodwatM~ . . . n

The purpose of this study is to determine the potential area of
flooding along St. Vrain Creek and to recommend a feasible and practical
plan fOt control of flooding in the teach within the study area. The
specific location of the study reach is shown in Figure-I. Th~ flood-
plain infor~ation provid~d in this r~port will b~ us~d by the local
agencies to regulate the land use of areas within the floodplain and
thus reduce future damages. I~ple~entation of the recowmend~d plan for
drainage improvements for the study reach will furth~r r~duce da~ages to
~xisting populat~d areas.

The cities, incorporsted to~ns, and counties ~itnin the study ar~a
may ptovide ~oning r~gulations:

Th~ &CoP~ of thE study includes the tollo~ing items:

1. M~et with representatlves of the City of Longmont, Boulder County,
as stated in Section 30-28-111 for tne ~ounty governments and Section 31- the Colorado Water Conservation Board and other public and private
23-210 for municipal ~overnments of the Colorado Revised Statutes 1973. agencies for basic information and data collection.

The Colorado Water Conservation Board has the po~er and duty:

t. Revie~ existing information and data related to the study reach
and conduct the necessary field surveys.

" , . , 1.0 dev,we IlJ1d ~Mmula.t.e met.hoM, m<!.aM and. ,,~
6M o'\',(lIg,01.g ",bOUt: .the g!tea-teA UUUZatiOOl 06 the wrt<<<I 06
the <lta.t.e <tiI.d the pilevei!.uol1. 06 6lood damagu. t.helle&tom and
to du,.(glUl.te and a."(Vlove <It.o!(m OJ!. 6loocW!a.IJ !(U:l1.o~6 chWlneu
0.... bMW, and to mAAe <lUch dv,.(gl1<l.tio!lA (tv(l.{labi:e t:o leg.(.6-
fuUve bodi.u, o~ cU.(.f/..6 <lild lI.l1..(nco!tF)Ma,.ted t.o....'.1-I; -t.o cou.ntJ.j
ptamung co"",.i4.I,.(oI1<l; and to bO<Vld<l 1)6 adjlVJtmentJ, c~ eill.....;
-U:COIt"o!tatedtOl<!>W; and. COt.tIlUU. 00 ,thw6We "

). Document the flood history of St. Vrain Creek.

* The tenl "u Chance Flood," "l"termediate Regional Flood," and "lOO-Y~ar
Fnquen~y Flood" can be used interChangeably as tney are defined by the
."",e type of flood event (see Glossary). Ho~~ve., for COOslstency, ~h.rc-
ever possible, the term "lOO-Year Hood" will be used in this report.

as stated in Section 37-60-106(1)(c) of the Colorado Revis~d Statutes 1973.

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