Planning & Management


394994 - Aging Numerical Tools and their Effects on Floodplain Mapping

Tuesday, June 5
2:00 PM - 3:30 PM
Location: Greenway GH

The National Flood Insurance Program was created in 1968. Many of the nation’s floodplains were delineated in the years following this legislation. At the time of the establishment of these Special Flood Hazard Areas, hydraulic modelers were armed with one-dimensional simple hydraulic models that used punch cards and ran on mainframe computers. These one-dimensional tools were often stretched to the limits of applicability by complex flow patterns. Many floodplains are still defined by these simple one-dimensional models and assumptions.
In recent years two-dimensional hydraulic modeling has become more prevalent amongst practitioners. Many of the current developed standards do not readily integrate with the newer two-dimensional tools because of the paradigms that existed at the time the methodologies were established.
It begs the question, what are the implications and impacts of current day multidimensional hydraulics on design and regulation?
The Foothills Parkway Project located in Boulder, Colorado sits at the confluence of this question. Three differently sourced floodplains converge at the project site, which seeks to provide improvements to trail connectivity across Foothills Parkway. The effective floodplains have been determined by varying degrees of hydraulic modeling, ranging from approximate methods, different era one-dimensional models, and a two-dimensional model. These models were created independently, without the modelers having the opportunity to know the details of the other models.
The presentation will focus on two questions as related to the Foothills Parkway Project:
• When compared to a modern day two-dimensional model that accounts for interactions and complex flow patterns within and between floodplains how do these aging numerical tools compare?
• How can the latest advancements in hydraulic models be used to navigate the requirements from current regulations?
It’s time for the industry to inspect these former assumptions and limitations in technology in a world of aging infrastructure and aging numerical tools.

Matthew Alan. Johnson, PE, CFM

Water Resources Engineer


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394994 - Aging Numerical Tools and their Effects on Floodplain Mapping

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