Hydrologic Hazard Communication

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Hydrologic Hazard Communication
NOAAs National Weather Service

• Britt Westergard
• Service Hydrologist
• WFO Jackson, KY
• WASIS Workshop, July 2006

NOAAs National Weather Service
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Major Challenges

• NWS issues flood warnings? Really?
• Products vs Information
• Verification vs Perception
• (focus on Flash Flood Warnings)

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Multi-tiered Concept
Products vs. Information

• Ready
• Outlooks
• Set
• Watches
• Go
• Warnings
• Advisories

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NWS Hydrologic Products
Products vs. Information

• Hydrologic Outlook (ESF)
• Areal Flood Watch (FFA)
• Flood Watch for Forecast Points (FFA)
• Flash Flood Warning (FFW)
• Flash Flood Statement (FFS)
• Flood Warning for Forecast Points (FLW)
• Flood Statement Follow-up to Flood Warning for
  Forecast Points (FLS)
• Areal Flood Warning (FLW)
• Flood Statement Follow-up to Areal Flood
  Warning (FLS)
• Flood Statement Areal Advisories (FLS)
• Flood Statement Flood Advisory for Forecast
  Points
• Hydrologic Statement (RVS)
• Hydrologic Summary (RVA)
• River and Lake Forecast Product (RVD)
• Hydrometeorological Data Products (RRx)
• Hydrometeorological Data Summary Products (HYx)

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Outreach
Products vs. Information

• We provide
• Actions to take (Turn Around, Dont Drown)
• Information sources (NWR, internet)
• Call-to-action statements in products
• But is the public
• bogged down by flash flood vs. areal flood vs.
  river flood?
• confused by watches and warnings? What about
  advisories?

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Flash Flood vs. River Flood
Verification vs. Perception

• Short-fused events (FFW) and long-fused events
  (FLW)
• River flood warnings
• related to hydrograph - graphical association
• would be relatively simple to introduce
  uncertainty graphics
• verification perception (exceed flood stage is
  cut dried)
• Flash flood warnings
• less quantifiable
• Verification and perception diverge?

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Verification Guidelines
Verification vs. Perception

• A Flash Flood occurs within 6 hours of a
  causative event
• River or stream flows out of its banks and is a
  threat to life or property.
• Person or vehicle is swept away by flowing water
  from runoff that inundates
• adjacent grounds.
• A maintained county or state road is closed by
  high water.
• Approximately six inches or more of water flows
  over a road or bridge. This
• includes low water crossings in a heavy rain
  event that is more than localized
• (i.e., radar and observer reports indicate
  flooding in nearby locations) and poses
• a threat to life or property.
• Dam break or ice jam release causes dangerous
  out of bank stream flows or
• inundates normally dry areas, creating a hazard
  to life or property.
• Any amount of water in contact, flowing into or
  causing damage of an above
• ground residence or public building and is runoff
  from adjacent grounds.
• Three feet or more of ponded water that poses a
  threat to life or property.
• Mudslide, rock slide or debris flow caused by
  rainfall (could possibly occur in a
• burned area with only light to moderate
  rainfall).

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Opportunities for Change

• Bridge gap between products and action taken
• Determine usefulness of product suite?
• Modify outreach strategy?
• Reach back to concept of products to re-evaluate?
• What is a flash flood anyway?
• Guidelines are based on safety is there a
  better basis?
• Convey uncertainty in short- and long-fused
  products