August 2015 Newsletter:

Hurricanes in North Carolina – Where, Why and How

We are currently entering what is considered the peak of hurricane season, and we thought this month it would be appropriate to discuss some general information regarding hurricanes in North Carolina, including their behavior, historical significance and local impacts.

Hurricanes occur in the North Atlantic Ocean and the Northeast Pacific Ocean. The same weather phenomena are called cyclones in the Southwest Pacific and Indian Oceans, and typhoons in the Northwest Pacific. These storms all form over warm water where high moisture conditions combined with the appropriate atmospheric pressure result in the significant rainfall and high wind speeds associated with hurricanes.

In the North Atlantic, hurricane season is typically considered to be from June until November, with its peak between mid-August and mid-October. Hurricanes in this region can form in the Atlantic, Caribbean Sea, and Gulf of Mexico, and can have significant impacts on all land masses throughout this area, including the eastern portion of the United States and North Carolina. Typically these storms begin as low pressure systems spinning off of the African continent and then traveling west.

Why Do Hurricanes Hit the East Coast?

One of the driving forces for hurricanes impacting the east coast of the US is a pressure system off of the coast of the country called the Bermuda High (BH). This high pressure system can change its size and westerly position throughout the year and over longer time scales based on its strength. Increases in its size, as well as westward migrations, are typically what result in hurricanes reaching landfall in the eastern US. Storms will typically move around the western boundary of the BH. Increases in the high pressure associated with the BH force tropical storms and hurricanes further west, ultimately making landfall in areas such as Florida and the Carolinas.

Hurricanes in North Carolina

From the mid-1800’s until 2011, North Carolina has been hit by upwards of 50 hurricanes. At least 12 of these were considered major, with the majority of the storms falling between a category 2 and a category 3 classification. Hurricane Hazel in 1954 was the only category 4 hurricane to hit the state. North Carolina has never been hit by a category 5 storm.

Hurricane Arthur impacted the Outer Banks in 2014 with winds in excess of 100 mph, and Hurricane Sandy passed by the state in 2012 creating massive storm surge. One of the last major hurricanes to significantly impact NC was Hurricane Irene in 2011. This storm hit the east coast of the state as a category 1 hurricane with winds in excess of 85 mph, destroying more than 1,100 homes. Prior to Irene, the last major hurricane to hit NC was Hurricane Isabel in 2003. This storm made landfall at Okracoke Island in the Outer Banks, causing significant coastal flooding as a category 2 storm before moving inland and damaging significant areas of the state.

The Outer Banks are a series of barrier islands along the east coast of North Carolina (see our  November 2014 newsletter). The fragile geologic conditions associated with these barrier islands, and their inherently dynamic conditions, make them significantly vulnerable to tropical storm and hurricane-force winds. The circular wind vectors associated with these storms result in extreme movement of beach sand parallel to the shoreline, causing significant erosion in some areas and then high levels of deposition in others. Additionally, the high storm surge associated with hurricanes in North Carolina leads to coastal flooding and breaching of the sand dunes along the Outer Banks, ultimately resulting in the westward (inland) movement of sand. Under natural barrier island conditions, these land masses would slowly move towards the mainland over time. However, because the Outer Banks have been developed for residential and commercial use, and are one of the state’s greatest tourist destinations, it becomes the work of municipalities to try and stabilize the coastline during and after these events to preserve the beaches, dunes, and coastline morphology.

The entire east coast of the US is vulnerable to hurricanes, and North Carolina’s location along the mid-Atlantic shore makes it a relatively frequent target for these storms. Please click on the links throughout this article to learn more about hurricanes impacting North Carolina, and make sure you are relatively prepared for effects such as flooding and power outages during the storm season!

July 2015 Newsletter Correction

Oops!  In our last newsletter we made a mistake. Here’s what we meant to say:

“The aquifers in the western 60 percent of the state (spanning the Piedmont and Blue Ridge zones) are typically zones of complex fractured igneous and volcanic rocks of the Paleozoic era overlain by regolith (soil, alluvium, rock).” We said Triassic, which are actually isolated basins within the older Paleozoic rocks.

Thank you, we work hard to make our newsletters both informative and accurate, always let us know if you see something that needs to be corrected.

The Association of Environmental & Engineering Geologists (AEG) is holding their annual meeting in Pittsburgh next month from September 21-26 at the Wyndham Grand Hotel Downtown.  This meeting is a great opportunity for environmental scientists, engineers, and geologists to meet and discuss the current state of the industry.  Pyramid will be exhibiting at the meeting as well as presenting a talk on geophysical surveys for karst mapping and void detection.  We hope to see you all there!

August Joke

Pyramid maintains the most up-to-date knowledge of the industry’s regulations, changes, and events, and we will continue to pass this information along to YOU.

Once again, thank you to all our loyal customers, vendors, and employees for your continued support. Pyramid can’t do it without you.

Sincerely,

DOUG CANAVELLO

Pyramid Environmental