Planning
Flooding, Storm Surge, etc.
For Hurricane preparedness see Hurricane FAQ - Hurricane Preparation
This Page:
General Flood Maps
Flood prone area planning maps
FEMA Flood Maps
Type in a specific address or town and map will take you to the '100-year' (1% chance every year, cyan color) and '500-year' (0.2% chance every year), yellow-ish/brown color) flood maps.
*Note: You have to zoom in further for flood layers to begin to appear!
*FEMA NFHL Viewer: https://hazards-fema.maps.arcgis.com/apps/webappviewer/index.html?id=8b0adb51996444d4879338b5529aa9cd
*Alternative link to same maps: https://msc.fema.gov/portal/home
Note: These maps are periodically reviewed and updated which may greatly change your estimated flood risk and insurance cost & requirements and don't include other flood chances such as the '1000-year' (0.1% chance every year) and other flood values. Some regions have not been reviewed for flood risk. The term '###-year' flood can be misleading as it's not a once every ### years flood event but actually the annual chance expressed as an annual value instead of a percentage. There can also be back to back severe floods of even the rarest rated flood levels. Additional information on recurrence level terminology by USGS: https://www.usgs.gov/special-topics/water-science-school/science/100-year-flood
Example FEMA flood map layer image as of June 2022
USGS Where to Find Maps, FAQ's & multimedia:
Sample map from USGS Water page
USGS Groundwater & Streamflow Conditions:
https://www.usgs.gov/programs/groundwater-and-streamflow-information-program
Sample USGS Streamflow map
NOAA river and tidal gauge map examples
Storm Surge Planning
Did you know you can actually plan for storm surge?
These interactive planning maps are used to determine a location's storm surge risk in possible future storms. The maps cover the regions of Texas to Maine, Hawaii, Puerto Rico, US Virgin Islands and Hispaniola. Maps are considered accurate down to the neighborhood level and show the potential storm surge water height above normally dry ground for each category of hurricane at any given location point. Change the storm 'Category' to see different potential water heights. Should an actual storm near land, a storm specific storm surge map will be issued by the US National Hurricane Center (NHC), referred to as the ‘Potential Storm Surge Flooding Map’, on the NHC’s home page. Storm surge is typically highest near the center (‘eye’) and gradually less water height the further from that point one goes.
The planning maps are useful for those who want to determine their surge risk, potential new home owners, insurance cost considerations, evacuation planning, etc. Most voluntary or mandatory evacuation orders are based on the storm surge risk. In the US, storm surge flooding is the most deadly aspect of a landfalling hurricane, accounting for nearly half of all deaths on average. Knowing your risk now can help save your life, lower insurance cost, reduce stress and anxiety, and give peace of mind (whether that’s knowing you are safe from surge or knowing around what level of storm would cause you to evacuate so you’re not wondering about should you stay or go, etc.).
National Storm Surge Hazard Maps portal: https://www.nhc.noaa.gov/nationalsurge/
Planning Map showing varying reach and heights of storm surge potential from Texas to North Carolina, USA for Cat5.
For additional information and further detail on these maps see my 'Hurricane FAQ's' page: 'Hurricane NHC Products', ' What are the National Storm Surge Hazard Maps (Planning maps)?'
"Nuisance" Coastal Flooding
High tide nuisance flooding is on the rise
It's called 'nuisance' flooding since this minor tidal flooding typically occurs only during some high tides and can be navigated by taking other streets or simply waiting for it to recede. But data shows it's occurring more frequently. And that's a problem.
NWS Charleston, SC USA 100 years of 'Nuisance' flooding data (1922-2021) showing increasing trend in days per year of occurrence. (Image source: NWS Charleston, SC). Additional info: https://www.weather.gov/chs/coastalflood
There are a variety issues that come with nuisance flooding, but they add up to a big headache and increased financial pressures. From first responders and city workers having to take time to temporarily monitor and close roads to corrosive salt water affecting vehicles. Decreased revenue for businesses and towns from coastal visitors & residents who shorten or postpone their outings. Damage to low lying infrastructure and storm drains. Saltwater intrusion further inland. Even water intrusion into low lying buildings.
NOAA high tide flood nuisance flooding example
No need for a storm, nuisance flooding can occur on sunny days. With sea level rise increasing each year along with sediment compaction, it all adds up over time to help create more nuisance flooding more often affecting more and more people and places.
"Nuisance" flooding Charleston, SC USA (Image credit: NOAA)
Side note: For Sea Level rise mapping, Miami has created a 3d interactive mapping impact system for their region here: https://mdc.maps.arcgis.com/apps/webappviewer3d/index.html?id=b92a9fa4ff8847bf97f3e628a195a398