Flooding on the Conestoga River


The Susquehanna Basin is one of the nation's most flood-prone areas and is vulnerable to a variety of flood risk including riverine flooding, flash flooding, and ice jam flooding. The Basin's topography, geology and nearly 49,000 miles of waterways are contributing factors to this flood risk. Additionally, the physical location of the Basin in the mid-Atlantic region of the United States subjects the watershed to a wide variety of climatic conditions, including tropical systems, strong thunderstorms associated with plunging cold fronts, and lake effect snowfall. While no one can prevent floods, understanding the flood risk associated with your particular location and appropriate response to National Weather Service issued watches and warnings can greatly reduce the risk to life and property.

New! Please visit a new story maps collection for the 50th Anniversary of Hurricane Agnes!

Current Conditions
National Weather Service Forecast Offices
Streamflow Information
Types of Flooding
Flood Inundation Maps

Inundation maps provide an expected area and depth of flooding associated with a specific stage at a locally relevant river forecast point (stream gage). The maps allow community residents to identify flood risk related to their own property location. Community officials and emergency managers can use the maps to understand severity of flooding associated with any particular mapped stage and plan evacuation routes and shelter needs.

How to Read a Flood Stage Forecast Map
  1. Locate an inundation map that provides expected area/depth of flooding relative to your local river gage
  2. Locate your property on the map.
  3. Determine the flood stage which will affect you. Consider not only water on your property, but also water preventing your evacuation.
  4. Listen for forecasts on the radio and television of stages at the stream gage used on the map.
  5. If the forecasted stage could affect you, begin emergency actions. If not, listen for revised forecasts until waters recede.

EXAMPLE: If you live in House A, river stages greater than 24 feet [indicated as 24 on the map] would affect your property directly. If your evacuation route goes through a low-lying area, emergency action may be required at a lower stage than the stage affecting your property.

History of Flooding
Tunkhannock Creek at Noxen, PA

The mainstem of the Susquehanna has flooded 14 times since 1810 – about every 15 years, on average. Even the Native Americans who once lived in the area told of frequent floods. Large-scale and localized flash floods both cause significant property damages and often result in the loss of lives. In June 1972, Hurricane Agnes caused the worst recorded flood in the Susquehanna basin - 72 people were killed throughout the Basin and damages were estimated at $2.8 billion. At the time, the Agnes flood was the nation's most destructive and costly natural disaster.

For comprehensive flood information, forecasts, and maps, visit Susquehanna Flood Forecast & Warning System.

Summary of the flood and performance of the Susquehanna Flood Forecast and Warning System during the June 2006 Flood