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The Unified Sizing Criteria

 Unified Sizing Criteria is a comprehensive approach to design stormwater management systems. It uses measurement standards to meet flooding, health, safety, and water quality goals. These criteria are used to design best management practices that meet desired treatment objectives. 

The Unified Sizing Criteria is used to manage stormwater with engineering techniques that protect our streams, rivers, and lakes. This approach mimics how Iowa’s original native prairie landscape and soils were able to soak in rainfall.


The Iowa Stormwater Management Manual

The purpose of the Iowa Stormwater Management Manual is to present planning and design guidelines for the management of stormwater quality and quantity in the urban environment. Jurisdictions with Phase I and Phase II NPDES stormwater permits may use alternative methods and design strategies for meeting post- construction requirements for stormwater quality improvement.