FLOOD04049

• County: Denver
• Community: All
• Stream Name: All
• Basin: South Platte
• Title: Riverine Erosion Hazard Areas Mapping Feasibility Study Executive Summary
• Date: 9/1/1999
• Prepared For: State of Colorado
• Prepared By: FEMA
• Floodplain - Doc Type: Educational/Technical/Reference Information

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Some analysis methods are based on the hypothesis that the stream system tends toward
a state of dynamic equilibrium in which the channel adjusts to changes in the water and
sediment supply regimes. These methods include simple equations called "regime
relationships," techniques based on mechanical stability conditions, and complex
ccmputer models. These equilibrium-based approaches have difficulties in accounting for
ever-changing land use ccnditions.

In addition to fluvial processes, numerous climatic, environmental and geotechnical factors
are involved, Hydrodynamically induced erosion and deposition and the occurrence of
mass failure of the streambanks drive channel cross sectional changes. Induced effects
include changes in roughness, bed material ccmposition, vegetation cover, and planform.
Prediction of cross sectional adjustments can only be acccmplished for site-specific
ccnditions after the most significant geomorphological factors have been identified.
Therefore, any prediction of channel geometry should be based on sound field
observations,

Literature Review

Of several hundred pieces of literature, 108 articles and reports were evaluated to survey
methods currently in use to predict channel changes. Of this set, 12 case studies were
selected for detailed review. The map below shows the geographic region covered by all
of the case studies ccmbined, The general features of the case studies are summarized
in the table on the next page.

Iowa Streambank
Erosion Study

Utah River Stability
Studies

Minnesota Stream
Meander Study

Platte River, NE
Geomorphic Study

u. Mississippi/Illinois
Waterway Study

King Co, WA
Channel Migration

San Diego Co" CA
Alluvial Studies

Arizona Lateral
Migration Standards

Rillito Creek Tucson AZ
Probabilistic Study

Santa Cruz River, AZ.
Geomorphologic Study

Location of case studies,

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