Green River Interim System-Wide Improvement Framework Mark - - PowerPoint PPT Presentation

Green River Interim System-Wide Improvement Framework

Mark Isaacson Division Director

FCD Advisory Committee July 27, 2016

Department of Natural Resources and Parks Water and Land Resources Division River and Floodplain Management Section

Pr Present esentation ation Over ervi view w

 PL 84-99 Program and SWIF

• Project Area and Context
• Advisory Structure
• Technical Studies

 Deficiency Action Plan  Capital Plan  Vegetation Plan  Interim Risk Reduction Measures  Funding and Implementation

• Lower Russell Project Example

Wha hat t is a Sy a System em Wide de Imp mprov rovement ement Fram amework

• rk (SWIF)

F)?

USACE SWIF policy, November 2011:

“A plan prepared by levee sponsors and approved by the USACE to implement system-wide improvements to a levee system (or multiple levee systems within a watershed) …” “… solutions will satisfy the multiple requirements that apply to levee systems (ESA, Tribal Treaty Rights, etc.) while allowing levee sponsors to remain eligible for PL84-99 funding while addressing deficiencies.”

• 1. Deficiency Action Plan to correct unacceptable
• r minimally acceptable deficiencies
• 2. Capital Plan to correct slope stability deficiencies

that cannot be corrected through routine maintenance actions

• 3. Vegetation Plan to guide the design,

maintenance and stewarship of shoreline vegetation on levees

• 4. Interim Risk Reduction Measures

Gre reen en Ri River er SWIF: F: Who ho is Inv nvolv

• lved?

ed?

• King County Flood Control

District, lead agency

• King County
• Green River Cities
• Muckleshoot Tribe
• USACE, FEMA, NOAA
• WRIA 9
• PSP, Ecology, WDFW
• Business community
• Environmental organizations
• Citizens

Tec echn hnica ical l Stud tudies: es:

Flood d Risk sk Assessm sessment nt

• Geomorphic Assessment – channel patterns and gradient,

stream incision, and damages to levees and revetments

• Geotechnical Assessment – levee stability, vulnerability,

and potential breach locations

• Hydraulic Assessment – flooding patterns, channel

capacity, and floodplain inundation (for flood flows of 12,000 to 26,800 cfs)

• Economic Analysis – Expected annual damages and

economic impacts Aq Aquatic, tic, Floodpla dplain, in, and nd Ripa parian rian Habitat tat

• Riparian vegetation – trees, shrubs, invasive species
• Aquatic Habitat – pools, large wood, edge habitat

Def efici iciency ency Actio tion n Pl Plan an

356 Deficiencies Across 11 Levees

1. Near-term actions: 2015-17

• Culvert CCTV, fence removal, flap

gates/tide flex, 2. Mid-term actions to complete within 6-year CIP (2016-2021) 3. Long-term actions: capital projects

• Capital plan – slope stability

4. Programmatic actions (ongoing) – vegetation and animal burrows 5. Monitoring actions (ongoing) – monitoring acceptable slope stability problems

Unacce ceptable ptable slo lope e stability bility Anim imal al burrows

Types of Problems…

Cul ulver erts ts – CCT CTV V an and Inspe pect/r t/rep eplace ce flap ap gat ates s an and Tidefl deflex Slope e stab ability ility – ran ange e from 1:1 to to 1.7:1 :1 slopes

…More Problems

Levee vegetati tion

• n – trees

s an and shrub ubs, s, rotting ting stumps, mps, inspe pect ctabi bilit lity Encro croachm hments ents – fences/gate s/gates, s, stai airs

Cap apital al Pl Plan an

11 minimally acceptable or unacceptable slope stability deficiencies on 4 levees

• Address slope stability deficiencies that

cannot be corrected by maintenance

• Achieve provisional level of protection

from flooding goal (500-year containment)

• Achieve factors of safety to support future

certification/accreditation

• Capital Projects:
• Lower Russell setback levee
• Tukwila 205 – 3 locations
• Horseshoe Bend – 3 locations

Tukw kwil ila 205

Vege egetat atio ion n Pl Plan an

• Goals – (1) levees and floodwalls function as

designed, (2) inspectability, (3) compliance with Clean Water and Endangered Species acts

• Achieve desired outcomes:
• Vegetation management and maintenance to

support annual inspections

• Improved riparian habitat and shade conditions

along PL 84-99 shorelines

• Alignment of flood risk management activities

with requirements to protect and restore natural resources

• Vegetation M&O:
• Annual brushing/mowing (before flood season)
• Hazard tree mgmt. (public safety, levee integrity)
• Vegetation maintenance on levees

Six Vegetation Management Zones

• Landward zone
• Landward slope zone
• Crest zone
• Upper riverward slope zone
• Riverward bench zone
• Lower riverward slope zone

Inte teri rim m Risk sk Red eductio uction n Meas easure ures

• Physical:
• Flood Warning Center and Program
• Flood Patrol and Levee Inspection
• Public Communications – preparedness,

education, understanding of residual risk

• Emergency Response (post-flood recovery)
• Animal Burrow Response Plan
• Tech studies, assistance, and consultation
• Flood hazard area regulations
• Effectiveness monitoring to improve

performance

• Physical:
• Sand bags
• Bulk bags (e.g., Hescos) –

temporary increase in height

• Earthen levee raising (low spots)
• Small capital projects for scour

and erosion

• Temporary rock placement

Fun undi ding ng an and d Imp mplem ement entat ation ion

SWIF implementation organized to resolve PL 84-99 deficiencies using a worst-first approach:

• Funding constraints limit pace of capital

project implementation

• Capital Project Costs = $85-101 million
• PL 84-99 Levee M&O costs = $780,000/yr
• Vegetation, encroachments, culverts,

burrows, assessments/monitoring

• IRRM Costs:
• Non-structural = $523,000 countywide
• Structural = variable (per LF)

Submittal of SWIF to USACE – Feb 2016

Fun unding ing an and Imp mplem emen entat atio ion

Project website:

Google “Green River System Wide Improvement Framework”

Questions?

Mark Isaacson, Division Director Water and Land Resources Division 206-477-4601 mark.isaacson@kingcounty.gov

Examp xample e Gr Gree een n River er Levee ee USACE CE PL 84-99 99 Rep epair airs

Kent t Shops ps-Nari rita ta Galli’s levee – toe ro rock k and wil illows Lil ily Point inte Segal ale – la launchab hable toe and flo floodwa dwall ll

Pr Projec

• ject

t Ar Area: ea: Gre reen en-Duw Duwamish amish Ri River er

• Water

ershed shed Area = 475 mi2

• Populati

ulation

• n = 370,000
• 10

10 cit itie ies

• Resid

identi ential, commerci cial, al, in industri strial and agricu culture ture

• Green

n Riv iver: r: 36 mil iles es of leve levees es and revet vetmen ents ts

• Howard

rd Hanso son n Dam (cons nstruct tructed d 1962 at RM RM 64.5)

• All

ll speci cies es of salm lmon

• n present

sent

Lower er Green een River er: : Cont ntext xt

Socio-Econo Economic mic

• $7.3 billion in floodplain

structures and contents

• 100,000+ jobs
• 100 million sf warehouse

+ distribution space (2nd largest on West Coast)

• Comprises 1/8th of the

GDP for WA State

• Annual taxable revenue of

$8 billion

• Boeing, REI HQ, Amazon

Fulfillment Center, Starbucks roasting plant

Lower er Green een River er: : Cont ntext xt

Salmon Populations & Habitat

• All species of salmon present,

including ESA-listed Chinook salmon

• Historical pop. approx. 38,000
• 40-year average = 5,000
• Low of 800 adults in 2009
• 25-65% hatchery origin
• Limited spawning in Lower Green

(above RM 24)

• Lethal water temperatures (> 23oC)

have occurred in Green River mainstem (July 2006); TMDL water quality standard is 16oC

• Tribal fishing rights

Location Leve vees es (#/mi miles) es) Revet vetments ents (#/mil miles es) Tot

• tal

Miles Duwamish (RM 5.5-11) 3 (0.6 miles) 22 (3.3 miles) 3.9 Lower Green (RM 11-32) 41 (17.7 miles) 45 (9.8 miles) 27.5 Middle Green (RM 32-44) 12 (1.9 miles) 13 (2.9 miles) 4.8 Tot

• tal

56 (20.2 miles es) 80 (16.0 miles es) 36.2 PL 84-99 levees (RM 12.4-30.8) 12 (16 miles)

Green een River er Fl Floo

• od Fac

acili lity ty Def efic icienci iencies es

• Aging system of levees – built to protect agricultural land uses, not regionally

significant urban areas

• Slope stability and toe scour issues
• Other deficiencies – culverts, vegetation, encroachments, animal burrows,

etc.

• Current containment = 12,000 cfs with variable freeboard
• Certification and Accreditation of Levees; FEMA mapping

Levees and Revetments

Levee ee Defic eficiencies iencies (PL8 PL84-99) 99)

Horse sesh shoe e Be Bend Levee e System m exa xample mple

Category (item)

Unacceptable Min. Acceptable Acceptable

Total Encroachments 20 6 26 Unwanted Veg. Growth 19 3 1 23 Other (e.g., culverts) 7 1 6 14 Slope Stability 4 1 5 Depressions/Rutting 4 4 Erosion/Bank Caving 4 4 Debris 1 1 Cracking 1 1 Total 26 38 14 78

Deficiency Action Plan Near-term actions: encroachments, animal burrows, debris, depressions, brushing Mid-term actions: vegetation Long-term actions: slope stability (and toe scour)

Ri Risk k Assess essme ment nt – Key Finding ndings

Geomorph rpholog logy

• Channel incision between 1986 and 2011 was a minimum of

1-2 feet everywhere, with maximum incision of 7-10.5 feet at channel bends in all four reaches of Lower Green

• Most damaged levees and revetments are located around

channel bends

• Channel locations with >5 feet of incision represent a

substantial risk of future damage to levees and revetments

Ri Risk k Asses essm sment nt – Key Finding ndings

Geot

• technical

hnical

• Most levees constructed in 1960s used river alluvium

(sand/ gravel), and dragline methods without compaction

• Levee stability analyses  shallow failure surfaces that

would not result in significant reduction of levee prism

– Considered a maintenance issue, with a low probability of causing a levee breach, but must be repaired

Cur urren rent t Cond nditi tion

• ns

s Repor

• rt: Hyd

ydraulic aulic Ass ssessment ssment

Hydrauli aulic c St Study y Area

Dis ischar harge ge vs. flo flood frequenc uency y at Au Aubur urn n (unreg egul ulat ated d and d regulat ated ed at HHD)

Flood lood Eve vent Flo low w at Aubu Auburn Gage e (cfs) Comm mment

2-yr yr 5% C.L.

9,900 2-yr events very similar, well below levee system crest

10 10-yr 95% % C.L.

11,900 Lowest volume 12,000 cfs range peak event

200-yr yr Median

12,600 Highest volume 12,000 cfs range peak event

100 100-yr yr 5% C.L.

15,100

• 500-yr

yr Median

18,800 Also used for the very similar 200-yr 5% event

500 00-yr yr 5% C.L.

26,800

Current rent Conditi ndition

• ns

s Repo port: : Hydra raulic ulic Assess essme ment nt (Inund nundation ation)

12,600 cfs 18,800 cfs 15,10 ,100 cfs

Levee overtopping that exceeds design protection will result in floodplain inundation of <1 to 10+ feet

Ri Risk k Assess essme ment nt – Key Finding ndings

Econom nomics ics

• HEC-FDA (Flood Damages Assessment) modeling

estimated system-wide estimated annual damages of $47.1 million

– National and Regional Economic Development (NED, RED) effects

• Present value damages (based on 50 years and 3.5%

discount rate) is $1.1 billion

– Analysis assumes all businesses remain and re-open following downtime caused by flood – There are 5,371 residential structures in planning area

Sh Shoreli eline/ ne/Ri Riparian parian Vegetati ation

• n and Aq

Aquatic atic Habit itat at

Findings dings

• Low diversity, quality and substantially modified from historical conditions
• Habitat dominated by glides; Riffles and pools limited downstream of RM 24
• Temperature impaired water body (TMDL), with lethal conditions for

salmonids in some years

Low Lower er Gr Green en Ri River er Ri Riparian parian As Aspec pect Pr Priorities

• rities

(M (Muc ucklesho kleshoot

• t Tribe

ibe 2013) 3)

Vege egetat atio ion n Pl Plan an – Thr hree ee sho horeli reline ne ty types es

Type pe A – Origina nal l (inv nvasiv asive vegetati tion)

• n)

Type pe B – Bioengi nginee neered red Repairs s Type pe C – Rece cent ntly ly Bui uilt t Capi apital Proje jects ts – Setback back levees, , floodwalls s

Lower er Rus ussell sell Road ad Levee ee Se Setb tbac ack

November 2006 Flood

Green n Rive ver r Natural ural Resources rces Area Relocat ated ed Van Doren’s Pa Park rk Ripar arian an Habitat tat Restorat ation

• n

Leve vee e Set etba back k and Green n Rive ver r Trail il Aq Aquatic atic and Ripar arian an Habitat tat Restorat ation

• n

Lower er Rus ussell sell Pr Project

• ject Location

cation

City of Kent – Right Bank Green River between River Mile 17.85-19.25 S 212th to Veterans Drive/S. 228th bridges

33

Gre reen Riv iver r Tra rail Van Doren’s Park rk Toe Scour & Overst steep eepened ned Slope

Lower er Rus ussel sell l Rd Levee ee Se Setb tbac ack

• Goal: Remove/replace existing flood containment system
• f levee/revetments to provide long-term flood protection,

improve riparian and aquatic habitat, and recreation

• Existing levee/revetments do not

meet current engineering design standards

• System prone to scour and slope

instability

• Unacceptable deficiencies in PL84-

99 (slope stability, encroachments, unwanted vegetation)

Lower Russell Road Levee 2006 Flood Photo

Flood Protection, Habitat Restoration and Recreation Enhancements