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Flood Plain Management


Londonderry Township has developed this page to help residents undertsand Township regulations, policies and practices regarding the identification of Special Flood Hazard Areas, mitigating flood hazard risk, and making available state and federal rescources

What is a Flood?

Chapter 27-1509 Floodplain Development of the Township Code of Ordinances defines a flood as "a temporary inundation of normally dry land areas."

What is a "Floodplain" or "Floodway"?

Chapter 27-1509 Floodplain Development of the Township Code of Ordinances has the following definitions:

Floodplain Area: "A relatively low land area which is subject to partial or complete inundation from an adjoining or nearby stream, river or watercourse and/or any area subject to the unusual and rapid accumulation of surface waters from any source.”

Floodway: "The channel of a river or other watercourse and the adjacent land areas that must be reserved in order to discharge the base flood without cumulatively increasing the water surface elevation more than one foot.”

These areas are known by the term "Special Flood Hazard Area" which is defined as "an area having special flood, mudflow, or flood-related erosion hazards, and shown on a Flood Hazard Boundary Map or Flood Insurance Rate Map...".(October 2022 FEMA NFIP Flood Insurance Manual, Appendix K Definitions) Londonderry Township has several areas of the Township identified as Special Flood Hazard Areas including areas along the Susquehanna river, Swatara Creek, Conewago Creek, and their tributaries.

1 Percent Annual Chance Floodplain

Am I in the Floodplain or Special Flood Hazard Area?

The Pennsylvania Emergency Management Agency (PEMA) in conjunction with Penn State University has developed a tool for residents throughout the Commonwealth to see if they are in an area with potential flooding concerns. This is not a regulatory product for the purposes of making determinations for permitting purposes but a tool for residents to learn more about potential flooding impacts. Please visit PA Flood Risk to explore the area around your property.

Township Ordinances and Policies

Londonderry Township adopted its most current regulations for floodplain management by Ordinance 2012-1 which became effective on July, 17th 2012. These regulations can be found under the Township Zoning Ordinance Chapter 27, Part 15 Floodplain Development of the Township Code of Ordinances.

Below you will find a various policy documents and templates related to Floodplain Management in the Township:

Information about On-Lot Sewage Disposal Systems on the Islands can be found here