Tag: damage

bookmark_borderClimate Change: A Hard Rain Is Falling

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by Daniel Brouse and Sidd Mukherjee

In a vacuum, everything falling to earth accelerates at 9.8 m/s^2 (32ft/s^2) [the downward speed increases at 9.8 m/s (32 ft/s) every second.]

Rain accelerates down to earth initially at 9.8 m/s^2, but air resistance slows the drops to a constant speed called the terminal velocity which depends on the size of the drop. “When all the parameters are considered the terminal velocity of a typical raindrop is calculated to be about 9 meters per second or 20 mph. A smaller raindrop of radius 0.15 cm has a terminal velocity of about 7 meters per second or 16 mph.” (1)

Velocity is only one factor in calculating the momentum of rain. The mass of rain also factors into the momentum.
p = mv
p = momentum
m = mass
v = velocity

“Climate change can affect the intensity and frequency of precipitation. Warmer oceans increase the amount of water that evaporates into the air. When more moisture-laden air moves over land or converges into a storm system, it can produce more intense precipitation — for example, heavier rain and snowstorms.” (2)

Part of the increasing momentum is transferred to the sides and upward increasing wind turbulence, as well as updrafts.

Most of the momentum is transferred upon impact. You may notice the rain bouncing higher off the streets and sidewalks. As rain becomes more massive, it will have greater momentum when it hits the ground. Ground without groundcover will be hit harder causing more damage. The groundcover will also be hit harder causing more damage.
* Concrete and asphalt will sustain more damage.
* Solar panels and roofs will sustain more damage.
* Trees and plants will sustain more damage.
* Food crops will sustain more damage.

1. “What is the speed of falling raindrops?” Kyle Hathcox, Glenn Marsch, David Ward (2001)
2. “Climate Change Indicators: Heavy Precipitation” EPA (2021)

The Human Induced Climate Change Experiment

bookmark_borderCoastal Change: Hurricanes and Extreme Storm Hazards

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Part of the Human Induced Climate Change Experiment

One of the goals of the USGS Coastal and Marine Geology Program is a national assessment of coastal change hazards. Hurricanes provide a powerful force that generates dangerous waves and currents capable of moving large amounts of sand, destroying buildings and infrastructure, and reshaping our nation’s coastline. Our research focuses on understanding the magnitude and variability of the impacts of hurricanes and extreme storms on the sandy beaches of the United States. The overall objective is to improve the capability to predict coastal change that results from severe storms. Such a capability will support management of coastal infrastructure, resources, and safety.

Hurricane Sandy Example

As Hurricane Sandy moved northward along the U.S. Atlantic coast in October 2012, U.S. Geological Survey scientists worked to determine where and how the storm’s waves and surge might dramatically reshape the beaches and dunes that stand between the storm and coastal developments. Through a complex modeling process that uses coastal elevations, wave forecasts, and potential storm surge, they predicted coastal change hazards, such as shoreline and dune erosion, that might be expected during a Sandy landfall.

Using the latest storm information available, USGS predicted the likelihood of a range of coastal change impacts within the region affected by the storm:

  • Dune erosion was very likely for the majority of the sandy beaches along the Maryland and Delaware coasts with widespread overwash also very likely in many areas.
  • Most of the New Jersey coast was very likely to experience extensive beach and dune erosion and many areas were very likely to overwash.
  • Along the south shore of Long Island, New York, the models predicted extensive beach and dune erosion as well as intermittent overwash.

Hurricane Sandy, the largest Atlantic hurricane on record, made landfall on October 30, 2012, and impacted a long swath of the Mid-Atlantic coastline. Many areas that had been hit by Hurricane Irene in August 2011 were again battered by strong waves and surge. The barrier islands were breached in a number of places and erosion of the beach and dunes occurred all along the Mid-Atlantic coast. This was the most destructive storm to impact this coastline since an extremely powerful nor’easter in December of 1992.

Following landfall, oblique aerial photography and lidar surveys of beach elevations were used to document the changes that occurred as a result of the storm. In addition, field measurements of the beaches and dunes were collected immediately after the storm. Comparisons of data collected before the storm show the nature, magnitude and spatial variability of the coastal response. These data will be used to further refine predictive models for storm-induced erosion.

Response Activities

Pre-landfall

Post-landfall (approx. 3-14 days)