A creative approach when 1D hydraulic modeling is the only option

Posted in: Energy, Water

2D hydraulic modelling floodplain 1DWhat is your recourse when an agency or client won’t accept a 2D hydraulic model of a complex floodplain project? This is exactly the dilemma that we recently faced when trying to address an important engineering issue using outdated technology.

In “2D or not 2D? A new era in hydraulic modeling”, I discussed the rapid developments underway in 2D hydraulic modeling, and how it’s more accessible and easier thanks to the addition of 2D modeling in HEC-RAS. But what if you are limited to only a 1D model, even though the situation being modeled is best suited for 2D?

The floodplain project being modeled is a prime example of an area that should be modeled in 2D. It has complex flow patterns and flow exchanges between streams on a very broad, flat floodplain. Rather than modeling the area easily with 2D, we are attempting to model it using 1D because the agencies involved will not accept a 2D model.

This is not uncommon. Many agencies find it difficult to adapt their guidelines to incorporate 2D modeling. The guidelines are often decades old and were developed around the principles of 1D modeling. Until the guidelines are adapted to incorporate 2D hydraulic modeling methods, consultants must adapt our 1D modeling techniques to model the situation at hand.

In the case of this client’s project, my colleagues and I are finding creative ways to incorporate the 2D flow patterns into a 1D hydraulic model. The 1D model is very complex, and to no one’s surprise, has difficulties. However, by dialing back the complexity of the model without jeopardizing the hydraulics, we are hopeful that that we can develop a 1D model that will function as intended.

As a 2D model isn’t acceptable for some agencies, we are also investigating development of a 2D model that will help inform development of the 1D model.

The lesson here is that even though a 2D model may be the ideal solution for certain modeling projects, a workable, usable 1D model can still be developed if needed. It just takes a little extra work, expertise and creativity to adapt the modeling to fit the situation at hand.


Nick Hathaway has always had a fascination with the movement and power of water. As a kid he would often spend summers at a local stream creating miniature dams and finding ways to manipulate the flow of the water. As a water resources engineer at Mead & Hunt, Nick now gets to work with water on a much larger scale. His main focus is on hydrologic and hydraulic analyses for projects related to dam safety, hydropower, levees, floodplain mapping, drainage studies and bridge design.

Other blog articles by Nick include:

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