Discussing current issues in engineering
Rapid snowmelt events have the potential to contribute to hazardous flooding in the United States and researchers are hoping to improve the design of infrastructure to withstand increased flooding levels from unseasonable snowmelt.
While snow usually melts gradually as seasons move from winter into spring, unseasonably warm temperatures and rain falls onto snow packs can lead to severe flooding events. This is putting newfound pressures on infrastructure designed to withstand rain precipitation and not additional water from snowmelt. Researchers from NASA’s Goddard Space Flight Center and the University of New Hampshire are hoping to improve current flooding estimates for civil engineers by incorporating snowmelt estimates into precipitation estimates for regions across the United States.
The national standards that civil engineers use to design flood resistant infrastructure (NOAA Atlas 14) exclusively uses liquid precipitation estimates and not water from snowmelt. In order to improve this standard, Eunsang Cho, a postdoctoral researcher at NASA’s Goddard Space Flight Center, and Jennifer Jacobs, a civil engineering professor at the University of New Hampshire, created a map that incorporates snowmelt into current precipitation maps for the continental United States.
Cho and Jacobs developed an estimate of snow water equivalent (SWE) that measures the amount of water contained in snowpack. They combined the SWE measure with NOAA’s precipitation data to provide a more accurate picture of NOAA’s current standard precipitation values.
They discovered that in snow-dominant regions, the incorporation of snowmelt increased total precipitation estimates up to 7.52 inches and nearly 17 inches for 25- and 100- year flood estimates respectively. They also found that 23% of the 44 states for which NOAA provides precipitation data, had higher precipitation values than those provided by NOAA.
Brian Henn, a scientist working on global climate models at Vulcan highlighted the fact that some of the most extreme snow melting events have occurred within the last 10 years, indicating that flooding events from snowmelt are becoming increasingly hazardous, especially when older infrastructure is not designed to withstand increasing flooding events due to precipitation from snow melts.
It is important to note, however, that NOAA Atlas 14 still works for most regions of the country where snowmelt is not a significant concern. But for mountainous regions of the western U.S. that contain heavy snowpack, NOAA values are becoming inadequate for estimating realistic precipitation amounts. Cho and Jacobs hope that their findings can improve current guidelines and further inform civil engineers so they can incorporate larger flooding events into the design of infrastructure. For more info you can read Cho and Jacobs’ complete published research article here.
Boulders Slowing Progress on the Chesapeake Bay Bridge Tunnel Expansion Project Now 2 Years Behind Schedule
Originally slated to be completed in 2022, the construction of a second Chesapeake Bay Bridge Tunnel in Virginia Beach is now officially two years behind schedule with the newest hinderance to timely construction being large granite boulders.
The tunnel expansion project is designed to add two additional tunnels parallel to the two current tunnels in order to end the two-way traffic congestion inside the existing tunnels. Construction of the first new tunnel started in 2017 and is being built under a shipping channel located nearest to Virginia Beach. The project was originally scheduled to be completed in 2022 with a price tag of $756 million. However, after a number of delays, the current projected completion date is 2024 with giant boulders being the newest obstacle.
The granite boulders, as large as 6 feet in diameter and weighing up to 25 tons, help make up two 5.25 acre manmade islands. In order to construct the new 5,700 ft long tunnel, the boulders need to be excavated in order to provide access for a tunnel boring machine (TBM) arriving from Germany this year. The TBM is designed to bore through soft soil, not hard granite boulders. Therefore, the construction contractors must pound steel pilings through the boulders as part of the excavation effort to provide access for the TBM. Mike Crist, the bridge tunnel’s deputy executive director of infrastructure described this process as driving a nail through granite rock.
As a result, construction progress is going much slower than anticipated due to the new boulder debacle and construction on the second parallel tunnel is not expected to begin before 2037. You can find more info on the Chesapeake Bay Bridge Tunnel project and the tunnel boring process here.
Colman Engineering, PLC
A professional engineering firm located in Harrisonburg, VA