NWS LIX - Hurricane Flooding Rain Threats and Impacts

EXTREME

Potential for extreme rainfall flooding

DEVASTATING TO CATASTROPHIC

  Potential Impacts: There is an extreme threat to life and property. There is a very elevated potential for higher rainfall amounts which will overwhelm local drainage capacity.

*  Scattered locations may experience major flooding, Many locations will experience minor to moderate flooding. Local drainage capacity in many communities may be overwhelmed.  

Major Flooding: Within 6 hours after heavy rain, rivers and tributaries overflow their banks in several places. Small streams, creeks, canals, and drainage ditches become dangerous rivers.  In flatter terrain, extensive inundation occurs covering both primary and secondary roads. In urban places, widespread inundation with streets and parking lots becoming rivers of moving water. Flood waters generally affect many buildings and roads

Note: In all tropical cyclone situations, listen for possible flash flood watches; move to higher ground if a flash flood  warning is issued for your area.

HIGH

Potential for major rainfall flooding

EXTENSIVE

  Potential  Impacts:  There is a critical threat to life and property. There is a elevated potential for higher rainfall amounts which will overwhelm local drainage capacity.

* Isolated locations may experience major flooding.

* Most locations will experience minor to moderate flooding. Local drainage capacities in many communities will be overwhelmed.

Major Flooding: Within 6 hours after heavy rain, rivers and tributaries overflow their banks in several places. Small streams, creeks, canals, and drainage ditches become dangerous rivers.  In flatter terrain, extensive inundation occurs covering both primary and secondary roads. In urban places, widespread inundation with streets and parking lots becoming rivers of moving water. Flood waters generally affect many buildings and roads

Moderate Flooding: Within 6 hours after heavy rain, rivers and tributaries become swollen and may begin to overspill their banks in a few places, especially in historically vulnerable locations. Small streams, creeks, canals, and drainage ditches overflow. In flatter terrain, expanded areas of rapid inundation occur around low-lying spots covering several secondary roads. In urban places, expanded areas of rapid inundation occur at several underpasses or poor drainage spots, with some streets and parking lots taking on moving water. Storm drains and retention ponds overflow. Flood waters generally affect several buildings and roads.

Note: In all tropical cyclone situations, listen for possible flash flood watches; move to higher ground if a flash flood  warning is issued for your area.

MODERATE

Potential for moderate flooding

SIGNIFICANT

   Potential Impacts:  There is a significant threat to life and property. There is a potential for higher rainfall amounts which could overwhelm local drainage capacity.

*  Isolated locations may experience moderate flooding, among scattered locations of minor flooding.

Moderate Flooding: Within 6 hours after heavy rain, rivers and tributaries become swollen and may begin to overspill their banks in a few places, especially in historically vulnerable locations. Small streams, creeks, canals, and drainage ditches overflow. In flatter terrain, expanded areas of rapid inundation occur around low-lying spots covering several secondary roads. In urban places, expanded areas of rapid inundation occur at several underpasses or poor drainage spots, with some streets and parking lots taking on moving water. Storm drains and retention ponds overflow. Flood waters generally affect several buildings and roads.

Note: In all tropical cyclone situations, listen for possible flash flood watches; move to higher ground if a flash flood  warning is issued for your area.

ELEVATED

Potential for some rainfall flooding

LIMITED

   Potential Impacts: There is an elevated threat to life and property. Higher rain amounts expected.  

* Isolated to scattered locations may experience minor flooding.

Minor Flooding: Within 6 hours after heavy rain, small streams, creeks, canals, and drainage ditches become swollen and overflow in a few places. In flatter terrain, quick ponding of water occurs around low-lying spots, especially in historically vulnerable locations. In urban places, quick ponding of water occurs at certain underpasses or poor drainage spots, especially in historically vulnerable locations. Storm drains and retention ponds become near-full and begin to overflow in a few places. Flood waters generally affect a few buildings and roads.

Note: In all tropical cyclone situations, listen for possible flash flood watches; move to higher ground if a flash flood  warning is issued for your area.

LITTLE TO NONE 

Little to no rainfall flooding anticipated

LITTLE TO NONE

               Potential Impacts:  No discernible threat to life and property.

* The likelihood for high rain totals is expected to be low.  Brief, heavy rainfall may occur.