FLOOD00540

• County: Statewide
• Community: State of Colorado
• Stream Name: All
• Title: Colorado Flood Hydrology Manual
• Date: 1/1/1995
• Prepared For: State of Colorado
• Prepared By: CWCB
• Floodplain - Doc Type: Educational/Technical/Reference Information

CHAPTER 6
APPROACHES TO FLOOD HYDROLOGY

There are a variety of approaches to flood hydrolo!JY. This chapter summarizes the approaches, while
Chapter 7 describes them in detail.,

(1) Frequency analysis of streamflow data

(2) Rainfall-runoff analysis of stol'm events

(3) Regional/Regression analysis

(4) Rational Method

(5) Envelope Curves
(6) Paleohyejrology

6,1,1 Freauency Analvsis of Streamflow Data, Where adequate streamflow data are available,
frequency analysis of such data can be performed to develop exceedance frequency estimates,
Frequency analysis is a method to infer the probability of exceedance of all possible discharge values
from observed discharge values, This process is accomplished by selecting a statistical model that
describes the distribution of discharges of the parent population, The parameters of the statistical
model are estimated from thE' sample or observEld discharge values,

Advantaaes

DisadvantaQmi

1, Generally provides most accurate
means of discharge' frequency analysis,

1, Usually not a stream gage exactly at
site of interest

2, Well documented, standardized
procedures (Bulletin 17B),

2, Assumes probability distribution model
fits population,

3, Streamflow based; does not rely on
precipitation data or rainfall-runoff models,

3. Assumes sample data is representative
of population,

4, If data is available, analysis can be
performed with less effort than exhaustive
deterministic data,

4, Assumes parameters of population can
be determined from sample data,

5, Cannot model effects of flood control
facilities or changes in basin
characteristics,

Colorado Flood
Hydrology Manual Ei,ll

DRAFT