PUB00035

• Year: 1998
• Title: Statewide River Rehabilitation and Floodplain Management Needs Inventory
• CWCB Section: Watershed & Flood Protection
• Author: Fritz, Browning, Matulik, Hyde
• Description: Summary document for work efforts that extended for over a year on the Inventory and Assessment of River Rehabilitatiom and Flood Plan Management Needs for the State of Colorado
• Publications - Doc Type: Tech Report

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CHAPTER II
FLOOD HISTORY AND STREAM
"" DETERIORATION
'"

FLOOD HISTORY

Colorado experiences, on average, 20 to 30 flood events annually. Every year, at least one of these events
equals or exceeds the 1 OO-year flood level, somewhere in the state. Over the past decade, Colorado has
experienced statewide flooding in 1993, 1995, and 1997. Western Colorado experienced major flooding in
1983 and 1984.

Colorado's total direct value flood damages are approaching $5 billion (in 1998 dollars), and fatalities
totaling more than 300 people. Secondary losses have not been quantified, but are estimated to be two to
three times greater than the direct damages. Secondary losses include economic development and trade,
tourism, agricultural production, and investment capital.

The state of Colorado formally started COllecting flood data in 1937, with authorizations and the creation of
the CWCs. Prior to 1937, the state's flood data was gathered and documented in individual reports and
from federal agencies.

Documented flood information and data are very valuable in the administration of a floodplain
management program. Past flood information is valuable in the projection and forecasting of future flood
activity for a floodplain or watershed, Nature has demonstrated that it will repeat itself on any given
watershed.

The scientific community uses past flood information for:
. Hydrological analysis,
· Hydraulic determinations,
· Economic justification of flood protection measures, and
· Justification for regulatory floodplain mapping and flood insurance requirements.

The management community uses past flood information for:
. Community awareness of flood dangers and risks,
· Community implementation of a flOOdplain management program, and
· Community endorsement of major economic development proposals,

The flood producing weather patterns in Colorado are not homogeneous. There is quite a bit of seasonal
variability and geographic variability, Therefore, Colorado experiences several types of natural flood
events, including stream specific floods, localized floods, and regional/statewide floods.

Section II - 1