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Stream Geomorphic Assessment supporting River Corridor and Floodplain Restoration and Protection in Vermont Mike Kline Vermont DEC Rivers Program
Stream Geomorphic Assessment supporting River Corridor and Floodplain
Restoration and Protection in Vermont
Mike Kline Vermont DEC
Rivers Program
!
VT ANR Stream Geomorphic Assessment Program
Watershed – Phase 1 Land use, Riparian, Channel, Floodplain and Valley Modifications
Reaches – Phase 2 Condition - Departure Adjustments - Evolution Sensitivity - Rate
Sites – Phase 3 Hydrology & Hydraulics Sediment Transport
Habitat Assessment
Bridge/Culvert/Dam
Public Safety and Property Protection
Very High Water Quality
Healthy Riparian Ecosystems
Economically and ecologically sustainable relationship with rivers
by managing toward dynamic equilibrium
Mitigate Flood and Fluvial Erosion Hazard Reduce Sediment and
Nutrient Loading
Restore / Protect Meandering, Connectivity,
Flows & Wood
Vermont River Corridor Planning
Limit Encroachments / Remove Constraints / Manage Emergency Measures / Restore Floodplain Function / Maintain Woody Buffers / Manage Stormwater
Stream Geomorphic
& Hydrologic
Assessments
Regulation of Stream
Alterations
River Corridor
and Floodplain Protection
River and Floodplain Restoration
Hazard Mitigation
River Corridor Planning
Data Analysis and
Mapping
Technical and Funding
Assistance
Education and
Outreach
VT Rivers Program
Agency of Natural Resources Agency of Commerce and Community Development Agency of Transportation Vermont Emergency Management Land Use and Development Commissions Agency of Agriculture
Watershed Associations Regional Planning Commissions Municipalities Conservation Organizations Local Land Trusts Consulting Community
EPA FEMA ACOE
FHA USFS
USFWS USGS USDC NOAA
NRCS/FSA
SGA & River Corridor Planning is being integrated into the planning, projects, and regulatory programs of our partners
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er W
inoo
ski H
eadw
ater
s
An understanding of fluvial processes and geomorphology is essential to protecting
and restoring watershed health
EPA Healthy Watersheds Program Recovery Potential Analysis
River Corridor Plans
Tactical Basin Plans
VT Surface Water Management Strategy
10 years of assessment completed by leveraging multiple funding sources
Phase 1 – 6,094 miles
Phase 2 – 1,760 miles
Assessments sponsored by local & regional groups
Status of statewide data and map development
Co-development and integration of statewide programs made possible by the availability of data.
On-line map and data retrieval
systems
SGAT Stream Geomorphic
Assessment Tool
A GIS Extension
VERMONT STATUTES CHAPTER 49: RIVER CORRIDOR PROTECTION
10 V.S.A. § 1422 (12) “River corridor” is the land area necessary for the natural maintenance or natural restoration of dynamic equilibrium conditions and for minimization of fluvial erosion hazards.
10 V.S.A. § 1422 (14) “Equilibrium condition” when water flow, sediment, and woody debris are transported by the stream in such a manner that it generally maintains its dimensions, pattern, and slope without unnaturally aggrading or degrading the channel bed elevation.
10 V.S.A. § 1427 Under the River Corridor and Floodplain Management Program, the secretary shall: (1) Assess geomorphic conditions (2) Delineate and map river corridors; and (3) Develop recommended best management practices for river corridors, floodplains, and buffers.
10 V.S.A. § 1428 (c) The Secretary of Administration shall offer financial incentives for municipal adoption and implementation of bylaws that protect river corridors and floodplains.
10 V.S.A. § 1421 POLICY: it is in the public interest to encourage and promote the protection of river corridors.
Managing Toward Dynamic Equilibrium Conditions: when the water flow, sediment, and woody debris produced by the watershed will be transported by the stream channel in such a manner that the stream maintains its dimension, general pattern, and slope with no unnatural aggrading (raising) or degrading (lowering) of the channel bed elevation at the stream reach scale.
Watershed Input: Sediment Load
Watershed Input: Hydrologic Load
Bed & Bank Resistance Stream Power
Erosion Deposition
Stream Geomorphic Assessments to define equilibrium conditions / departures
Changes in channel, floodplain and valley characteristics are assessed to understand how depth, slope, and boundary resistance influence hydraulic geometry, stream power, and the sorting and distribution of sediment and organic material.
Reach-scale Stressors
Site vs. Reach-scale Analysis.
Stream flow and sediment load characteristics are assessed as the primary controlling factors influencing equilibrium, hydraulic geometry, and stream power.
Watershed-scale Stressors
Why is this stream eroding?
Managing in context Streams adjusting from 200+ years of Channel, Floodplain and Watershed Modifications:
!! Deforestation !! Snagging and ditching
!! Villages, farms, roads and rails
!! Dams and diversions !! Gravel mining !! Channeling - berming !! Undersized Culverts !! Stormwater
Transport process accentuated in 3/4 assessed VT Streams Disequilibrium: Uneven distribution of erosion and deposition process
Cover, Feeding, Refuge, and Reproductive Habitats Affected
Abandoned Floodplain
Current Floodplain
Unconstrained re-distribution of stream energy and sediment
Resolving Conflicts with an understanding of constraints at larger temporal and spatial scales
Uneven distribution of stream energy and sediment Constraints on
channel adjustment
Longitudinal Profile
Elevation of Floodplain
Bed Profile
Channel Incision
Traditional river management created short-term solutions to protect property but ignored the cumulative effects that lead to large-scale disequilibrium, major channel adjustments and disastrous property losses.
Decrease transport and increase storage, to:
•! Distribute river energy
•! Attenuate sediment and nutrient production
•! Reduce flood hazards and
•! Retain habitat structure and complexity
% C
hann
el S
traig
hten
ing
Watershed Size (sq. miles)
0102030405060708090100
0 50 100 150 200
"!
""!
"""!
"#$#!
On average 31.4% of Vermont assessed streams have been historically straightened and channelization.
Stages II and III of planform evolution
Statewide Data = Policy to begin managing beyond the channel
River Corridors are designed to accommodate the erosion and storage processes associated with dynamic equilibrium at the end of the channel evolution process.
Qs x Sed. !""##$##%##&'()*+
,*-.-/012*##!##3(4*5
River Corridor
Meander Centerline
MCL
Vegetated Buffer
Belt Widths are a function of !! drainage area = D !! stream width = W !! valley slope & width !! stream sensitivity
Valley Toes
B Belt
Width
1
N = 60r2 = 0.6768
Vermont Meander Width Ratios Low gradient, unconfined alluvial streams
Belt Width B = 3.7W1.12 Williams, 1986
Using Williams Regression
Meander width ratio B/W = 5 to 6 channel widths
%!&!'()'*+,-./0!12'()(*3+!!
B/W = 6 to 8.5
For a 50 foot wide stream B/W = 6.7
N = 66
R2 = 0.67
Toe of right valley wall
Toe of left valley wall
Flow
2006: A = 12.38x0.75
R2 = 0.95
2006: W = 13.1x0.44
R2 = 0.91
2006: D = 0.96x0.30
R2 = 0.872002: D = 1.22x0.25
R2 = 0.59
2002: W = 10.18x0.5
R2 = 0.78
2002: A = 12.21x0.75
R2 = 0.85
1
10
100
1000
1 10 100 1000
Drainage Area (sq.mi.)
Dep
th (f
t.) /
Wid
th (f
t.) /
Are
a (s
q.ft.
)
Vermont Hydraulic Geometry
Curves
Boundary Condition - Buffers, grade controls, erosion, bed/bank materials, snagging, windrowing
Hydrologic - Land use, stormwater, diversions, flow regulation, dams
Sediment Load - Land Use, depositional features, bank erosion, mass failures & gullies, upstream incision, and tributary rejuvenation
Stream Power - Channelization, berms, dredging, grade controls, encroachments, head cuts, beaver dams
Watershed Scale Stressors
Reach Scale Stressors
River Corridor Stressor Maps
Sediment Regime Departure to understand ecological processes and equilibrium at the watershed scale:
!! floodplain connectivity !! transport & storage
River Corridor Planning
River Corridor Planning
Watershed-Scale Strategies:
Drainage and Stormwater Management Gully and Erosion Control Buffer Establishment and Protection Removal of Structural Encroachments River Corridor Easements River and Floodplain Restorations
Reach-specific Projects:
Protect Sensitive River Corridors Plant Stream Buffers Stabilize Stream Banks Arrest head cuts and nick points Remove Berms and other constraints to
flood and sediment load attenuation Remove/Replace Structures
(e.g. undersized culverts, low dams) Restore Incised Reaches Restore Aggraded Reaches
Ecological Integrity and
Fish & Wildlife Resource
Water Quality and Quantity
Public Safety and Property
Protection Strategies to Protect and Restore Floodplains
& Stream Equilibrium
!!Functioning floodplains and river corridors create an intersection for the protection of public values
Water Quality: Annual mean phosphorus loads from three Lake Champlain tributaries during water years 1991-2011.
Winooski River
Phos
phor
us L
oad
(mt/y
r)
0
100
200
300
400
500
600
700
19911992
19931994
19951996
19971998
19992000
20052006
20032004
20012002
20072008
20092010
2011
Missisquoi River
Phos
phor
us L
oad
(mt/y
r)
0
100
200
300
400
500
600
19911992
19931994
19951996
19971998
19992000
20052006
20032004
20012002
20072008
20092010
2011
Otter Creek
Phos
phor
us L
oad
(mt/y
r)
0
50
100
150
200
250
300
350
19911992
19931994
19951996
19971998
19992000
20052006
20032004
20012002
20072008
20092010
2011
1991-2010 mean 1991-2010 mean
1991-2010 mean
410
147
206
121
383
139
Modeling in Missisquoi Basin Indicates that approximately 1/3 of TSS and TP loading is associated with bank erosion.
Irene flood flow data showing the protection of downstream communities when attenuation assets are in place and functioning.
Winooski River
Rutland – 15,700 cfs Flow
Middlebury – 6,180 cfs
At 3 of 7 restored sites In 2 years
1,419 cu. yd. of sediment 1.3 metric tonnes of total phosphorus
Sediment Deposition along Restored Black Creek Floodplains
Berm Removal to Restore Attenuation Asset
Excavate berm and terrace for new floodplain
Gully Brook, Traverse Farm!
Passive Habitat Restoration
Habitat Assessments Stream type and community-specific departure analyses
Process and component-based evaluations of:
!!Step-pools
!!Plane Beds
!!Riffle Pools
!!Ripple-Dunes
Channel Evolution and Sensitive Stream Biota
EPT richness rebounds as channel evolves back to equilibrium
I Stable
II Incised
III Widening
IV Narrowing
V Stable
Data from Stormwater Impaired Streams and Attainment Streams Fitzgerald et al. 2012
Habitat starts with large scale processes
! "#$% "$#&'()*"+','- +.//&0'()*"+
! ! !
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#$"%"&
'#( '#&
"!# )!*$
#&!
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! "! '! #! %! &! *! $! (! )! "!! "'! +,-.
1'2./34$00'()*"+
5$67&#'84'!"#$%"$#&9 1687 Structures
83% < 70% BF
54% < 50% BF
Applying the Vermont Culvert Geomorphic Compatibility and AOP Screening Tool
(Infrastructure impacts habitat by creating discontinuities and significantly altering
hydrologic and sediment regimes)
Public Safety Historically Focused on Inundation
Channel evolution confounds flood mapping and results in the under-estimation of risk in Vermont.
Not in a Mapped Floodplain
Trying to control and contain floods everywhere is a recipe for disaster.
Vulnerability Assessments Stream Geomorphic Data makes the case that….
Escalating Costs, Risks, and Ecosystem Degradation
Floods and Property Damage
Dredge, Berm and Armor
Encroachment
"#$$! $%&'!
Less vulnerable !4(5! !!(5!
Same Vulnerability 3(5! 3(5!
More Vulnerability 3(5! 6(5!
Breaking the Cycle
Bennington’s Restoration of the Roaring Branch Floodplain
Communities taking new approaches to post-flood recovery.
Flood Resilient Communities Program: Upon completion of geomorphic sensitivity assessments under Section 1427 of this title, the secretary shall provide to municipalities and regional planning commissions with river corridor maps. The secretary of administration, after consultation with the state agencies of relevant jurisdiction, shall offer financial incentives, when funds are available, for municipal adoption and implementation of bylaws under 24 V.S.A. Chapter 117 that protect river corridors and floodplains.
Avoidance Strategy: Where possible, limit encroachments on straightened and incised channels to minimize losses, avoid cost of maintaining channel works, and create restoration potential.
Incentives
Message to Towns Encroachments on straightened and incised channels equals property loss, cost of maintaining channel works, downstream impacts, and a loss of recovery options ($$$).
Go beyond the concept of riparian buffers.
Protect river corridors and floodplains to accommodate floods and fluvial processes; distribute and dissipate energy; store sediment and woody debris; and create and maintain habitat.
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River Corridor and Floodplain Protection
River corridor protection (FEH) area maps and updated floodplain maps provided to municipalities for their use in land use planning & regulation –! Model bylaws and ordinances
–! Pre-Disaster Mitigation Plan
–! Municipal Incentives
Communities w/ river corridor plans 170
Draft river corridor maps completed 84
River corridor and floodplain maps adopted as a bylaw / ordinance 39
river corridor and floodplain protection bylaws
40
Protecting Key Attenuation Assets
Cessation of channelization to increase/allow for sediment storage at key watershed locations
River Corridor Easement used to secure:
!!Channel Management Rights
!!Riparian Buffer
!!Corridor Development Rights
31 easements with 722 acres
closing on another 15 easements with 234 acres
We’ve been chasing the river for too long!
Vermont River and Floodplain Management Moving away from the concept that rivers are static systems.
Repeated and costly efforts to control long lengths of rivers as static channels is proof that channelization with structural measures is an unsustainable public policy.
Stream Geomorphic Assessments and River Corridor Planning are giving Vermont a science-based foundation for cost-effective alternatives.
