What does fluvial geomorphology mean

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What does fluvial geomorphology mean?

• Fluvial action of running water
• Geomorphology
• Geo Earth
• morph form
• ology study of
• The study of how running water shapes the
  landforms on the Earths surface

Suncook River at Epsom
Fluvial erosion wearing away of river beds and
banks by action of water, prevalent at very high
flows and in flood events
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Cold River, Alstead, 2005
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Warren Brook, Alstead, 2005
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Piscataquog River Watershed
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Fluvial Erosion Hazard (FEH) Program

• The science of fluvial geomorphology provides the
  tools that can allow us to assess streams to
  determine the stability of reaches along a river
  channel.
• Reach stream section with relatively uniform
  characteristics
• Geomorphic assessments
• On reaches so that zones of future potential
  erosion can be delineated

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Fluvial Erosion Hazard (FEH) Program

• Benefits
• Targeting of resources to minimize future erosion
  impacts caused by erosion, protecting lives,
  property, and infrastructure, thus enhancing
  public safety.
• Identify areas adjacent to channels, including
  infrastructure (i.e., bridges/culverts) most
  potentially threatened by future fluvial erosion
• Enhancement of existing NFIP zones

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NFIP
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NFIP
Assumes a static, stable, unchanging channel,
with water that rises out of the channel spilling
onto the surrounding floodplain, inundating
adjacent lands, property, and infrastructure.
Elevation
Above mean sea level Land Water
140
140
120
120
100-year flood elevation level
100
100
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FEH
Assumes an active, unstable, dynamic channel,
where the power of water in a high flow event can
erode adjacent banks, and in some cases, cause a
complete shift in the channel path, removing
adjacent lands, property, and infrastructure.
Elevation
Above mean sea level Land Water
140
140
120
120
100-year flood elevation level
100
100
River undercuts stream bank, shifts course, and
erodes into valley wall
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Edge of valley
Existing path of river channel
After major flood, new path of river
channel. Plus, all attendant erosion.
River has access to erode within its valley, with
increasing risk as sensitivities increase. Not
elevation specific.
River has access to valley
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Geomorphic Assessments

• Reach break determination
• In-field data collection (assessment of present
  physical condition and sensitivity to future
  adjustment)
• Classification of each reach

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Fluvial Erosion Hazard Maps
Hazard Type MD6 Moderate Four (4) Channel
Widths
Hazard Type VH7 - Very High Six (6) channel widths
Areas vulnerable to erosion, based on river
process captured using FEH methodology. Sensitivit
y ratings used to determine widths, and so the
appropriate width is already built into the zone.
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Fluvial Erosion Hazard Maps
Town of Exeter from recently completed Exeter
River assessment . . . The end product
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The end product . . . FEH Zones that can be used
to target resources to minimize future flood
impacts, saving lives, property, and
infrastructure.
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Fluvial Erosion Hazards Program in New Hampshire

• Right now
• Ammonoosuc River
• Isinglass River

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Fluvial Erosion Hazards Program The Future

• Lamprey Watershed
• Lamprey mainstem
• Little
• North Branch Lamprey
• North
• Piscassic (lower reach)

• Cocheco Watershed
• Cocheco mainstem
• Mad
• Axe Handle Brook

FEH zone delineation proceeds in same manner as
for Exeter
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Next Round of FEH
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Fluvial Geomorphic Assessments (FGA) Fluvial
Erosion Hazard (FEH) Mapping
Whos involved?