Civil Engineering Consultant – Stormwater Management, Grading & Drainage
HEC-RAS is a fantastic resource. While most hydraulic modeling software programs are expensive, HEC-RAS is freely available. However, the low (or lack of) price tag does not diminish its value to the industry. Many brilliant engineers have spent many years (some even decades) making this program what it is today. The program has been updated … Read more
Culverts are an important aspect of our infrastructure. However, they are so common that they seem obvious in some ways, but without them, life would be more complicated. A roadway has to have gentle curves horizontally and vertically. As a result, this means that roadway designers can only go around some obstacles – including rivers … Read more
Unsteady flow modeling is often fretted with instability issues. This is especially true when modeling mixed flow in an unsteady flow model due to the complexity of modeling a mixed flow regime (subcritical, supercritical, and hydraulic jumps). This complexity is associated with the nature of the unsteady flow equations (St. Venant equations). The St. Venant … Read more
Unsteady flow modeling tends to be more complex and time-consuming than steady flow modeling. Instabilities become more of an issue, and addressing these instabilities is both an art and a science. Unfortunately, many modelers end up spending hours tweaking their crashing model only to find out they only needed to change one setting to fix … Read more
HEC-RAS allows users to define areas that contain water that will not be actively moving downstream. These areas are referred to as ineffective flow areas. Appropriately defining ineffective flow areas is an important part of the modeling process. However, representing ineffective flow areas in HEC-RAS models tends to be somewhat subjective in nature, and every … Read more
On Flood Insurance Rate Maps (FIRM), a regulatory floodway is designated by blue and orange diagonal hatching. The floodway is useful because it facilitates land use planning that regulates development in flood-prone areas. Although floodway delineations are based on hydraulic analyses, one could argue that floodway mapping is both an art and a science. This … Read more
When creating hydraulic models using the Hydrologic Engineering Center’s River Analysis System (HEC-RAS), most users rely on the user interface to assemble information correctly. However, it can be helpful to understand the file types that make up an HEC-RAS project. This is because understanding these file types can help modelers more easily understand how a … Read more
Jarrett’s equation can be used to estimate an accurate Manning’s n value for steep streams. This is important because steep mountain streams should, in many cases, be assigned a higher Manning’s n value than what is shown in Chow’s Manning’s n value tables (which is a table many hydraulic engineers reference regularly). For example, Chow’s … Read more
Cut lines are an important aspect of georeferenced HEC-RAS models because they represent the geospatial location of your cross sections in plan view. If you are having issues with the placement of your cross sections, I recommend looking at the cut lines table. The following blog post will describe how to use the cut lines … Read more
Runoff is an important aspect of the hydrologic cycle. Understanding the amount of water that will be conveyed to hydraulic structures such as storm drains, pipes, culverts, or waterbodies is critical to designing effective stormwater infrastructure. For this reason, it is important that hydrologic and hydraulic (H&H) modelers accurately depict the relationship between rainfall and … Read more