final presentation - alluvial fan floodplains_maxcomp

Mark Edelman, AICP – Arizona State Land DepartmentSallie Diebolt – U.S. Army Corps of Engineers

Doug Williams, AICP – Flood Control District of Maricopa County

Source: "Gigantic Alluvial Fan Being Uplift by New Fault" by Wing‐Chi Poon ‐ self‐made; along North Highway in Death Valley National Park, California, USA.. Licensed under CC BY‐SA 2.5 via Commons – https://commons.wikimedia.org/wiki/File:Gigantic_Alluvial_Fan_Being_Uplift_by_New_Fault.jpg#/media/File:Gigantic_Alluvial_Fan_Being_Uplift_by_New_Fault.jpg

https://commons.wikimedia.org/wiki/File:Gigantic_Alluvial_Fan_Being_Uplift_by_New_Fault.jpg

Death Valley, CASource: "Gigantic Alluvial Fan Being Uplift by New Fault" by Wing‐Chi Poon ‐ self‐made; along North Highway in Death Valley National Park, California, USA.. Licensed under CC BY‐SA 2.5 via Commons –https://commons.wikimedia.org/wiki/File:Gigantic_Alluvial_Fan_Being_Uplift_by_New_Fault.jpg#/media/File:Gigantic_Alluvial_Fan_Being_Uplift_by_New_Fault.jpg

Apex

Toe


Apex

Toe

Toe

Apex


Estimated Cost of Flood Damage in a 2000 Sq.Ft. Home:Depth of Water

EstimatedLosses

1” $20,9206” $39,15012” $52,2202’ $62,8804’ $74,580

Data Source:Flood Control District of Maricopa County/National Flood Insurance Program


Rawhide and Reata Wash AO Floodplains – NE Phoenix/N Scottsdale

Traditional/Historic Solutions:

Dam

Ditch

Divert

Palm Springs, CA – 1938: Palm Canyon Drive bridge washout over Tahquitz WashSource: Palm Springs Historical Society

Historic Case Study: Palm Springs, California area

Tahquitz WashPalm Canyon Wash


Palm Springs, CA: Tahquitz Wash and Palm Canyon Wash floodplainsSource: FEMA

Tahquitz Wash

Palm Canyon Wash



Capture, Containment, and Channelization of Palm Canyon and Tahquitz Washes

Tahquitz WashPalm Canyon Wash


Alluvial Fan Apex Control and Channelization – Rancho Mirage, CA

Federal Jurisdiction:• FEMA/NFIP

• FHA• Clean Water Act Section 404 EPA/Army Corps of Engineers

Local Jurisdiction:• Floodplain Manager• Flood Control District

Clean Water Act Section 404Sallie Diebolt – US Army Corps of Engineers

Case Study: Rawhide Wash (NE Phoenix/N. Scottsdale)

Doug Williams – Flood Control District of Maricopa County

BUILDING STRONG®And Taking Care Of People!

US Army Corps of EngineersBUILDING STRONG®

Section 404 Clean Water Act Permitting

Sallie DieboltChief, Arizona BranchRegulatory DivisionLos Angeles District

November 5, 2015


We all want Clean Water!

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Reporter Richard Ellis dips his hand in the Cuyahoga River on a boat trip in the 1960s

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August 1, 1969“No Visible Life. Some river!

Chocolate-brown, oily, bubbling with subsurface gases, it oozes rather than flows. "Anyone who falls into the Cuyahoga does not drown,"

Cleveland's citizens joke grimly. "He decays." The Federal Water

Pollution Control Administration dryly notes: "The lower Cuyahoga

has no visible life, not even low forms such as leeches and sludge

worms that usually thrive on wastes." It is also—literally —a fire

hazard.”

http://www.sxc.hu/browse.phtml?f=download&id=1204768&redirect=photo

http://www.time.com/time/

http://en.wikipedia.org/wiki/File:Environmental_Protection_Agency_logo.svg


Cuyahoga River Today

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Regulatory Mission

• Protect aquatic resources

• Allow reasonable development

• Fair, timely, and balanced permit decisions

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What is Section 404?

Section 404 of the Clean Water Act (1972, as amended)Required for the discharge of dredged or fill material into waters of the U.S.Common projects are construction, maintenance, and repair activities in the waters of the U.S.

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Regulatory Process

1) What is the scope of the project?

2) Is there geographic jurisdiction?

3) Are there regulated activities?

4) What type of permit is needed?


Regulator’s Process






Scope of ProjectLocation information• Vicinity map• Coordinates• Directions to site• Permission to access

Clearly define project area boundaryDescribe all proposed activitiesSingle and complete project

Recent, good quality aerial photos28


Design/Planning (Conventional Approach)

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Street


Design/Planning (Modified Approach)

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Regulatory Process






Geographic Jurisdiction

Physical and biological indicators of flowWetland boundary

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Geographic JurisdictionRivers/Streams

Dry Washes/Arroyos

Ponds/Lakes*

Wetlands*

Constructed Canals/Laterals** fed by or conveys natural drainage flows

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Two Types of Jurisdictional Delineations

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Preliminary JD- Non-Binding- Assume all likely areas are jurisdictional- No Significant Nexus Analysis- Does not require EPA approval- Allows projects to move forward

Approved JD- Binding- Definitive re non-jurisdictional areas- Significant Nexus Analysis- Requires EPA approval


Clean Water RuleRulemaking to clarify jurisdiction under Section 404Current status???

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Regulatory Process






Regulated Activities

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Any activity that results in ground-disturbing activities (i.e., dredging or filling) within waters of the U.S.• Fills (e.g., for construction of buildings, parking

lots, etc.) • Roads (culverts)• Rip-Rap• Grading (moving material from one area to

another within the waterway)• Stockpiles• Utility Lines• Mechanized removal of vegetation


What Is NOT Regulated Under Section 404?

Excavation “Scoop and haul”FencesDrivingHerbicidesOther activities regulated by Section 402 (SWPPP)

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Regulatory Process






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Types ofSection 404

Permits

Individual§ 404 Permit

Impacts toWaters

of the U.S.

any amount of wetland impacted

No § 404Permit

Non-NotifyingNationwide§ 404 Permit

No Impacts

Impactless than orequal to1/10 acre

NotifyingNationwide

§ 404 Permit (PCN)Or may affectcultural resources

or federally listed species

Impact greaterthan 1/10 acre,but less thanor equal to

½ acre

•2–4 months +•Jurisdictional delineationrequired

Start work today!Obey conditions.

6 months to 1 year +

If need jurisdictional delineation,Corps review is usually 2–3 months

Start work today!No conditions!

Impact greater than ½ acre or

Regional General Permit

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Certain emergency situations


Nationwide Permit (NWP) Program

Corps reviews and reissues the NWP program every 5 years

Current set of NWPs:Issued March 19, 2012Expire March 18, 2017

Verification letter from Corps is generally valid until March 18, 2017

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RGP 63 Definition of Emergency

An “emergency situation” is present where there is a clear,

sudden, unexpected, and imminent threat to

life or property demanding immediate action to prevent or mitigate

loss of, or damage to, life, health, property or essential public

services (i.e., a situation that could potentially result in an

unacceptable hazard to life or a significant loss of property if

corrective action requiring a permit is not undertaken immediately).

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Sequential ApproachAvoidMinimizeMitigateDocument Compliance with permit terms

and conditions

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Compensatory MitigationComply with the Mitigation RuleMitigation BanksIn-lieu fee programsPrescott Creeks Preservation AssociationArizona Game and Fish DepartmentLa Paz County Endangered Species FundSuperstition Area Land TrustTucson Audubon Society

Permitee-responsible mitigation

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Prescott Creeks

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Plan Ahead!Designate team member responsible for Section 404 matters – have Section 404 agenda item in meetingsEarly and continuous resource assessment• Identify jurisdictional waters• Establish resource values (cultural, biological)• Avoid and minimize impacts where practical • Continuously reassess project direction for Section 404 impacts

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Arizona Regulatory Branch

3636 N. Central Ave., Suite 900

Phoenix, AZ 85012-1939602-230-6949 (General)

[email protected]

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Flood Control District of Maricopa County MISSION: Reduce county resident’s risks of injury, death, and property damage due to flooding

Major Activities

o Floodplain & Watershed Studies

o Floodplain Regulation

o Flood Hazard Mitigation • Structural• Non-structural

o Operations & Maintenance • Dams, channels, levees, and basins

Alluvial Fan Flooding

Apex

Alluvial Fan Characteristics in Maricopa CountyLow SlopesWater Flood DominatedDistal From Mountain FrontLimited Aerial Extent (small)Relatively Small Peaks (high Q/area)Low Flood Volumes (flashy)Transitions to Sheet Flow

Ahwatukee Fan Pre & Post Development

Hayden & Pinnacle Peak 1993 & 2013North Scottsdale

TP will insert 2 photos

Need for Solutions for Rawhide Wash

• Largest Flood Hazard in Study Area

• High risks to people and properties

• Feasible solutions that could:• Mitigate the hazards• Reduce the risks• Benefits > Costs

Rawhide Wash Hazards: Wash is Unpredictable

Rawhide Wash Flood Hazards

• High Flows (9600 cfs)

• Active Alluvial Fan o Flow paths can change

o High uncertainty

o Structural solution is required to:

- Mitigate the flood hazard

- Revise the floodplain maps (FEMA)

Add Photo of Rawhide Apex

Why is Rawhide Wash Hazardous?Active Alluvial Fan = Wash is Unpredictable

Rawhide Wash: Floodplain & Regulatory Aspects

1. Flood insurance required (mortgaged houses)

• Approximately 4,000 properties in floodplain

• Flood insurance premiums

o Annually $1.6 Million

o Over 50-year period estimate $155 Million

2. Development requirements

• Elevate houses

• Construct infrastructure to address Rawhide Wash flows

1. Mitigate the Alluvial Fan Flood Hazard• Ensure flow path certainty

• Control sediment

2. Reduce the floodplain• Revise from AO to AE

• Removes >2,000 acres from the floodplain

3. Facilitate Economic Development• More land to develop

• Less expensive to develop

Rawhide Wash Goals:

No Action Alternative

• Accept the risk

• 4,000 properties remain in floodplain

• High costs to Future and Existing Property Owners

– Flood Damages

– Flood Insurance

– Development Costs

NO ACTION• 6500 acres/4000 properties

remain in floodplain

• 500 structures at high potential flood risk

• High costs to Property Owners

– Flood Insurance

– Existing & Future

– Development Costs

• Cost Estimate: $224 Million

BUILD• Build structures to reduce the risk

& size of floodplain

– Addresses uncertainty

– Levee, floodwalls, basin, and grade control structures

– Floodplain would be remapped to remove floodplain for about 3,400 properties/3000 acres

• Moderate costs

– Cities & County

– Future Developers

Flood Control Mitigation SolutionsTwo Options: Convey or Detain Flood Water

• Conveyance o Natural Washeso Channelso Leveeso Storm Drainso Flood walls

Note: Bold and underlined are the options being considered for Rawhide

Flood Control Mitigation SolutionsTwo Options: Convey or Detain Flood Water

• Detention o Basins

o In-line o Off-line

o Dams

Note: Bold and underlined are the options being considered for Rawhide

Street view of basin above

In-line Detention Basin

Basin to Reduce Flow

• Considering two potential general locations

• Offline basino Low or frequent flows

remain in wash to sustain vegetation

o Flood flows go into basin

Jomax Road

Happy Valley Road

Pima Road

Basin to Reduce Flow

• Flows would be less than the current peak discharge of 9,600 cfs

• Flows contained between levees and floodwallso Fewer levees may be

neededo Fewer walls may need to

be reconstructed

Joax Road

Happy Valley Road

Pima Road

Offline Detention Basin

Recommendation Development

. Collaborative process

Continuous input on how problems are fixed

• Identify potential solutions

o Non-structuralo Structuralo Floodplain redelineations

Acceptable

Fiscally ResponsibleCompatible

Developing Safety on Alluvial Fans

Few trees in area are gone

January 19, 1997

Location of bankJanuary 2, 1964

Deepen foundationfootings

Elevate structures

Developing Safely on Alluvial Fans

Floodway – requires structural measure

Apex solution

Developing Safely on Alluvial Fans

Floodway – requires structural measure

Engineered erosion control and concentration of flows

POSSIBLE CHANNEL ALTERNATIVE

Lessons Learned

Every Fan is Unique

Determine Type of Hazard

Consensus Driven Solutions

Fan Development can be– Extremely Costly & Complicated

QUESTIONS

final presentation - alluvial fan floodplains_maxcomp

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