Channel Migration Zones:Channel Migration Zones:What? Why? Where?What? Why? Where?

Shorelands and Environmental Assistance ProgramShorelands and Environmental Assistance Program

Washington Department of EcologyWashington Department of Ecology

Patricia L. OlsonPatricia L. Olson

What is a channel What is a channel migration zone?migration zone?

WAC 173-26-020(6):WAC 173-26-020(6): "Channel migration zone "Channel migration zone (CMZ)" means the area along (CMZ)" means the area along a river within which the a river within which the channel(s) can be reasonably channel(s) can be reasonably predicted to migrate over predicted to migrate over time as a result of natural time as a result of natural and normally occurring and normally occurring hydrological and related hydrological and related processes when considered processes when considered with the characteristics of the with the characteristics of the river and its surroundingsriver and its surroundings

Alluvial ChannelMorphology

Channels withCMZ’s

ChannelPatterns

Meandered

Wandering

Anastomosed Braided

Meandered

channels

Lateral & downstreammigration

Cohesive banks

Not cohesivebanks

Meandered

channels

Entrenchederosive

Incised

EntrenchedLess erosive

Anastomosed channels

Braidedchannels

Wanderingchannels

Why identify channel migration zones?

Rivers migrate, depositing and eroding as they go Rivers migrate, depositing and eroding as they go

Impact to property in migration and avulsion areasImpact to property in migration and avulsion areas

Geo and flood hazardsGeo and flood hazards

•Highest concentration of Spring Chinook redds45% of total for Twisp River

•Reach with the most area, length and diversity of side channels and wetlands per river mile

Provide habitat biodiversity and beneficial floodplain servicesProvide habitat biodiversity and beneficial floodplain services

Tied to no-net-loss of ecological functionsTied to no-net-loss of ecological functions

Update of Shoreline management regulationsUpdate of Shoreline management regulations Required channel migration zones (CMZ) be identified in Shoreline Required channel migration zones (CMZ) be identified in Shoreline

Management Program (SMP) updatesManagement Program (SMP) updates

WAC 173-26-186WAC 173-26-186: Shoreline Master Programs must include : Shoreline Master Programs must include standards to implement a number of actions including CMZ standards to implement a number of actions including CMZ delineation delineation

WAC 173-26-201(3)(c)(vii):WAC 173-26-201(3)(c)(vii): a required inventory item in the a required inventory item in the Shoreline Master Program watershed characterization and Shoreline Master Program watershed characterization and critical areascritical areas

WAC 173-26-221(2)(c)(iv)(B):WAC 173-26-221(2)(c)(iv)(B): development in the CMZ development in the CMZ should be limited to that which does not interfere with migration should be limited to that which does not interfere with migration and cause adverse impacts to property or public improvements and cause adverse impacts to property or public improvements and “net loss of ecological functions” and “net loss of ecological functions”

WAC 173-26-221(2)(c)(iv)(A):WAC 173-26-221(2)(c)(iv)(A): identified as critical freshwater identified as critical freshwater and riparian habitatand riparian habitat

WAC 173-26-221(3)(b-c): Applicable shoreline master programs WAC 173-26-221(3)(b-c): Applicable shoreline master programs should include provisions to limit development and shoreline should include provisions to limit development and shoreline modifications and reduce flood hazards in the CMZmodifications and reduce flood hazards in the CMZ

WAC 173-26-221(3)(b) is fairly specific on what WAC 173-26-221(3)(b) is fairly specific on what should be considered in identifying channel should be considered in identifying channel migration areas:migration areas: The channel migration zone should be established to The channel migration zone should be established to

identify those areas subject to channel movement identify those areas subject to channel movement based based on the historic record, geologic character and evidence on the historic record, geologic character and evidence of past migrationof past migration. Human and natural changes may alter . Human and natural changes may alter migration patterns. migration patterns. Consideration should be given to Consideration should be given to changes from human and natural alterations and their changes from human and natural alterations and their effect on future migration patterns.effect on future migration patterns.

For management purposes, the extent of likely migration For management purposes, the extent of likely migration along a stream reach can be identified using evidence of along a stream reach can be identified using evidence of active stream channel movement over the past active stream channel movement over the past one one hundred yearshundred years. . Evidence of active movement can be Evidence of active movement can be provided from historic and current aerial photos and provided from historic and current aerial photos and maps and may require field analysismaps and may require field analysis

Ecology’s RoleEcology’s Role

Review and approve SMP update documentsReview and approve SMP update documents

Provide technical assistance to local governments Provide technical assistance to local governments by developing tools to:by developing tools to:

Make decisions on need for CMZ assessmentMake decisions on need for CMZ assessment

Determine approach, level of analysis and appropriate Determine approach, level of analysis and appropriate methods methods

Outline minimal acceptable standards of analysisOutline minimal acceptable standards of analysis

Provide technical assistance for implementing Provide technical assistance for implementing shoreland regulations where there are CMZsshoreland regulations where there are CMZs

Provide technical assistance for managing CMZsProvide technical assistance for managing CMZs

Background—existing Ecology technical frameworkBackground—existing Ecology technical framework

2002—A directed retreat of scientists was 2002—A directed retreat of scientists was convened in anticipation of inclusion of CMZ convened in anticipation of inclusion of CMZ delineation in Shoreline Master Programs and delineation in Shoreline Master Programs and flood hazard reductionflood hazard reduction

TopicsTopics Controls to channel migrationControls to channel migration

Effects of natural and human-induced disturbanceEffects of natural and human-induced disturbance

Develop definitions for the CMZDevelop definitions for the CMZ

Discuss methods to delineate a CMZDiscuss methods to delineate a CMZ

ProductProduct A Washington Department of Ecology technical documentA Washington Department of Ecology technical document

Cygnia Rapp, R.G.; Timothy Abbe, Ph.D., R.G, 2003 Cygnia Rapp, R.G.; Timothy Abbe, Ph.D., R.G, 2003

http://www.ecy.wa.gov/biblio/http://www.ecy.wa.gov/biblio/0306027.html0306027.html

Role of existing frameworkRole of existing framework

The framework provides:The framework provides: Information on the scientific basis for delineating Information on the scientific basis for delineating

channel migration zoneschannel migration zones A resource intensive approach with a general discussion A resource intensive approach with a general discussion

of methodsof methods Sources of relevant dataSources of relevant data Field data collection methodsField data collection methods

It is notIt is not : : The only approachThe only approach Mandated to be used by local governmentMandated to be used by local government Replacement for other approaches used outside Replacement for other approaches used outside

shoreline or floodplain jurisdictions (e.g., forest practices shoreline or floodplain jurisdictions (e.g., forest practices methods)methods)

A compendium of other possible approachesA compendium of other possible approaches

The framework does not provide information to The framework does not provide information to assist local governments to:assist local governments to:

Make decisions on need for CMZ assessmentMake decisions on need for CMZ assessment

Determine approach, level of analysis and appropriate Determine approach, level of analysis and appropriate methods methods

Outline minimal standards of practice for the Outline minimal standards of practice for the assessmentassessment

Provide information to develop consistent criteria for Provide information to develop consistent criteria for identifying level of hazardidentifying level of hazard

Now where do we go? Now where do we go?

Bigger Picture—longer term goalBigger Picture—longer term goal Develop a decision support system Develop a decision support system

Provides a framework for making decisions and Provides a framework for making decisions and answering questions, for exampleanswering questions, for example

Do I need to do a CMZ delineation?Do I need to do a CMZ delineation? What level of effort is needed?What level of effort is needed? What approach and methods are appropriate? What approach and methods are appropriate? What resources will it take?What resources will it take?

Purpose: Purpose: Provide a logic sequence that can be followedProvide a logic sequence that can be followed

Recommend appropriate methods based on geomorphic Recommend appropriate methods based on geomorphic characteristics, land use management, and resources characteristics, land use management, and resources

A web survey for local government planning A web survey for local government planning and/or shoreline staff was sent out August 2005and/or shoreline staff was sent out August 2005 To obtain information to improve our ability to provide To obtain information to improve our ability to provide

technical assistance to local governmentstechnical assistance to local governments

To identify where CMZ assessments have been doneTo identify where CMZ assessments have been done

Desired outcomeDesired outcome Information that will direct us in providing appropriate Information that will direct us in providing appropriate

technical information on CMZ assessments in relation to:technical information on CMZ assessments in relation to: Shoreline Master Plans (SMP) updates Shoreline Master Plans (SMP) updates Critical area ordinance (CAO) adoptions Critical area ordinance (CAO) adoptions Integration of CMZ and on-going floodplain hazard mappingIntegration of CMZ and on-going floodplain hazard mapping

Actions to dateActions to date

Survey resultsSurvey results Sent to 38 countiesSent to 38 counties

18 responded 18 responded

Primary resource concerns for conducting a CMZ assessment Expertise—94% Sufficient data—71% (particularly air photos and channel

surveys) Cost—75% Adequate guidance—53%

Resources that would help Examples of completed delineations—82% Grant funding assistance—73% Guidance document on CMZ—65% Technical assistance—64% 7 Time—62% Hazard ratings—55%

Some counties have completed CMZ’s Some counties have completed CMZ’s

Based on methods described in the CMZ technical reportBased on methods described in the CMZ technical report

Jefferson, Pierce, King, Yakima (Naches)Jefferson, Pierce, King, Yakima (Naches)

Some counties and municipalities have draft CMZ Some counties and municipalities have draft CMZ delineationsdelineations Whatcom, Snohomish, Yakima, Okanogan, MasonWhatcom, Snohomish, Yakima, Okanogan, Mason DarringtonDarrington

Most communities began before SMP updateMost communities began before SMP update CAO, Comprehensive Flood Hazard Management PlansCAO, Comprehensive Flood Hazard Management Plans

Desired elements on maps Erosion hazards—90% Meander belts—70% Gradations of risk—70% Avulsion potential—60%

Useful guidance for implementing & managing CMZs Limitations on new subdivisions—60% Limitations on new shoreline modifications—67% Geotechnical analysis guidance—60%

Other concerns Property owner concerns—88% Implications to the regulations of my jurisdiction—75%

1-day workshop of professionals who have done CMZ 1-day workshop of professionals who have done CMZ assessments for local governmentsassessments for local governments Provide a forum to:Provide a forum to:

Discuss a minimal standard of practice for CMZ assessments Discuss a minimal standard of practice for CMZ assessments based on physical processes (consider past land use activity on based on physical processes (consider past land use activity on physical processes) and local government needsphysical processes) and local government needs

Appropriate and scientifically credible methodsAppropriate and scientifically credible methodsDiscuss criteria for consistent hazard ratingsDiscuss criteria for consistent hazard ratingsDiscuss consistency in methods and mapping/GIS productsDiscuss consistency in methods and mapping/GIS products

Desired outcomesDesired outcomes Framework for minimal standard of practiceFramework for minimal standard of practice Criteria for developing consistent hazard ratingsCriteria for developing consistent hazard ratings

Preliminary QuestionsPreliminary Questions

How much CMZ analysis is enough? What is the minimal How much CMZ analysis is enough? What is the minimal standard of practice givenstandard of practice given Physical processes Physical processes Local government needs/objectives e.g., planning, Local government needs/objectives e.g., planning,

implementation, hazard assessmentimplementation, hazard assessment

Can a logical sequence/roadmap be developed for local Can a logical sequence/roadmap be developed for local governments? governments?

Decision system: “if, when and to what extent”Decision system: “if, when and to what extent”

Decision Tree—CMZ Decision Tree—CMZ AssessmentAssessment

Step 1: Determine where channel migration analysis is

needed

Migration analysis needed

or desired?

Yes

Step 2a: Determine minimum approach and methods based

on physical attributes and scale for SMP characterization and

inventory phase

Step 2b: Determine level of effort based on environmental

values and existing infrastructure

Step 2c: Choose appropriate approach and method for land

use objectives and level of effort

Step 3: Determine reach breaks

Step 4: Assess and map CMZ, erosion and avulsion hazards

for jurisdiction

Step 5: Identify reaches that maybe exempted from CMZ

regulation (DMA)

Step 6: Identify hazard zone levels (optional)

Migration analysis needed?

Is a channel migration assessment needed?Is a channel migration assessment needed? Are there migrating rivers and/or other geo-Are there migrating rivers and/or other geo-

hazards such as eroding banks or avulsions?hazards such as eroding banks or avulsions? Where?Where?

Step 1: Determine where channel migration analysis is

needed

Indicators of current or past channel change?

(1) Is channel confined?

Yes(2b) Is channel gradient <17%

No

(2a) Is channel gradient ≤4%

(3) Evidence of channel avulsions, vertical change,

delta or alluvial fan distributary channels?

Yes

YesStep 1a: Identify

channel types and processes

No

Yes

No

No(4) Evidence of bank erosion?

Yes

Bank erosion hazard analysis

STOP

No

Channel type: Straight and

narrow?

Step 1b: Create a general map of

channel types and processes

Yes

Step 2

No

Step 2a: Determine minimum approach and methods based on physical attributes and scale for SMP characterization and inventory phase

Basin scale Reach scale Site scale M B A W M B A W M B A W

Watershed characterization

1 1 1 1/ 2 2/ 1 2/ 1 2/ 1 2/ 3 3/ 1 3/ 1 3/ 1 3/ 2

Step 2b: Determine level of effort based on environmental values and existing infrastructure

Environmental value high moderate low

Level of effort

+100 low low low

75- 100 moderate moderate low

50- 75 high moderate moderate

Geomorphic process possible: Erosion, flooding,

avulsion in years

<50 high high moderate

Infrastructure value low moderate high

Level of effort

+100 low low low

75- 100 low moderate moderate

50- 75 moderate high high

Geomorphic process possible: Erosion, flooding,

avulsion in years

<50 moderate high very high

Step 2c: Choose appropriate approach and method for land use objectives and level of effort

Level of effort Low Moderate High Pattern M B A W M B A W M B A W Basin scale

Comprehensive 1 1 1 1 1 1 2 2 2 2 2 2 Salmon Recovery 1 1 1 1 1 1 1 2 2 2 2 2

Planning

Restoration 1 1 1 1/2

1 2 2 2 2 2 2 3

Flood hazard reduction 2 2 2 2 3 3 3 3 4 4 4 4 Hazard assessment Geo hazard 2 2 2 2 3 3 3 4 4 4 4 5 Regulatory Infrastructure 3 3 3 4 4 4 4 5 5 5 5 6 Mitigation 2 2 2 2 3 3 3 3 4 4 4 4 Environmental 2 2 2 2 3 3 3 4 4 4 5 5 Reach scale

Comprehensive 3 3 3 3 3 3 3 4 4 5 5 5 Salmon Recovery 3 3 3 3 3 3 3 3 4 4 4 4

Planning

Restoration 3 3 4 4 3 3 4 4 5 5 5 6 Flood hazard reduction 3 3 4 4 4 4 5 5 5 5 6 6 Hazard

assessment Geo hazard 3 3 4 4 4 4 5 5 5 5 6 6 Regulatory Infrastructure 3 3 4 4 4 4 5 5 5 5 6 6 Mitigation 3 3 4 4 3 3 4 4 5 5 5 6 Environmental 3 3 4 4 4 4 5 5 5 5 6 6 Site scale

Comprehensive 3 3 3 3 3 3 3 4 4 5 5 5 Salmon Recovery 3 3 3 3 3 3 3 3 4 4 4 4

Planning

Restoration 3 3 4 4 3 3 4 4 5 5 5 6 Flood hazard reduction 3 3 4 4 4 4 5 5 5 5 6 6 Hazard

assessment Geo hazard 3 3 4 4 4 4 5 5 5 5 6 6 Regulatory Infrastructure 3 3 4 4 4 4 5 5 5 5 6 6 Mitigation 2 2 3 3 3 3 4 5 5 5 5 6 Environmental 2 2 3 3 3 3 4 4 4 4 5 5

Exemptions--Exemptions--WAC 173-26-221(3)(b):WAC 173-26-221(3)(b):

Within incorporated municipalitiesWithin incorporated municipalities and urban growth areasand urban growth areas, areas , areas separatedseparated from the active river channel from the active river channel by legally existing by legally existing artificial channel constraintsartificial channel constraints that limit channel movement should that limit channel movement should not be considered within the channel migration zone.not be considered within the channel migration zone.

All areas All areas separatedseparated from the active channel from the active channel by a legally existing by a legally existing artificial structure(sartificial structure(s) that is likely to restrain channel migration, ) that is likely to restrain channel migration, including transportation facilities, built above or including transportation facilities, built above or constructed to constructed to remain intact through the one hundred-year floodremain intact through the one hundred-year flood, should not be , should not be considered to be in the channel migration zone.considered to be in the channel migration zone.

In areas In areas outside incorporated municipalities and urban growth outside incorporated municipalities and urban growth areasareas, channel constraints and flood control structures , channel constraints and flood control structures built below built below the one hundred-year flood elevation do not necessarily restrict the one hundred-year flood elevation do not necessarily restrict channel migration and should not be considered to limit the channel migration and should not be considered to limit the channel migration zonechannel migration zone unless demonstrated otherwise using unless demonstrated otherwise using scientific and scientific and technical informationtechnical information..

http://www.ecy.wa.gov/programs/sea/sma/st_guide/jurisdiction/CMZ.html http://www.ecy.wa.gov/programs/sea/sma/st_guide/jurisdiction/CMZ.html Channel migration site with WAC citations and linksChannel migration site with WAC citations and links

http://www.ecy.wa.gov/biblio/0306027.html http://www.ecy.wa.gov/biblio/0306027.html Rapp and Abbe technical reportRapp and Abbe technical report