Stormwater LID and Storm EZ

Low Impact Development (LID) is a voluntary approach to stormwater management that can benefit both the economy and the environment by reducing infrastructure costs, increasing lot yields and enhancing water quality protection.

The Definition of LID

A development is considered LID when the volume of runoff leaving the site after development matches the volume of runoff before development.  In addition, and LID project should maintain adequate flows to the streams and weltands on the site rather than piping stormwater to a single low point.

What is Storm-EZ?

Storm-EZ is a spreadsheet based on the NRCS Discrete Curve Number Method and current research on stormwater control measures. Designers enter data about the site plan and the stormwater control measures that will be used. Then, Storm-EZ reports how closely the project matches the pre-development runoff volumes. Storm-EZ can also be used to judge compliance with the "basic treatment" approach (85% TSS removal) or a hybrid approach of some LID practices used in conjunction with basic treatment.  

The use of Storm-EZ is voluntary. Designers may continue to use the old application and supplement forms. However there are a number of advantages to using Storm-EZ, including:

  • Storm-EZ can be used for projects that are LID, basic treatment or a combination of the two.
  • Storm-EZ streamlines the state stormwater permit application form, the BMP Supplement Forms and the Operation and Maintenance Agreements into one all-inclusive tool.
  • Storm-EZ estimates the impact of LID techniques on peak discharge rates from developments for flood control events, including the 5-, 10-, 25-, 50- and 100-year storms.
  • Developments that provide runoff volume match will meet any state-implementd stormwater program, including Coastal Counties, ORW, HQW and SA waters.  
  • Local goverments with state stormwater programs such as Water Supply Watershed, Phase II and NSW are allowed and encouraged to accept LID projects as meeting the requirements of their programs.


Storm-EZ  (Updated 9/3/15)

LID & Storm-EZ Fact Sheet

Memo on Coordination between LID & NSW Programs

NC LID Guidebook

NC BMP Manual

U.S. EPA LID Guidance


Contact Annette Lucas at (919) 807-6381 or or Mike Randall at (919) 807-6374 or