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William Krabill

Publications and source records attributed to William Krabill.

6 recordsLinked to original sources
USGS2011

Airborne laser study quantifies El Niño-induced coastal change

Winter storms during the 1997–1998 El Niño caused extensive changes to the beaches and cliffs of the west coast of the United States, a NASA-NOAA-USGS investigation using a scanning airborne laser has found. For example, near Pacifica in central California, the cliff eroded locally as much as 10–13 m landward during the El Niño winter, at least 40 times the long term average erosion rate. However, only several hundred meters away the cliff was stable. This variability in cliff response may be related to differences in local beach changes where an accreting beach protected part of the cliff and an eroding beach exposed another part to attack by waves.

Pacific Coast↗
USGS2004

Barrier island morphodynamic classification based on lidar metrics for north Assateague Island, Maryland

In order to reap the potential of airborne lidar surveys to provide geological information useful in understanding coastal sedimentary processes acting on various time scales, a new set of analysis methods are needed. This paper presents a multi-temporal lidar analysis of north Assateague Island, Maryland, and demonstrates the calculation of lidar metrics that condense barrier island morphology and morphological change into attributed linear features that may be used to analyze trends in coastal evolution. The new methods proposed in this paper are also of significant practical value, because lidar metric analysis reduces large volumes of point elevations into linear features attributed with essential morphological variables that are ideally suited for inclusion in Geographic Information Systems. A morphodynamic classification of north Assategue Island for a recent 10 month time period that is based on the recognition of simple patterns described by lidar change metrics is presented. Such morphodynamic classification reveals the relative magnitude and the fine scale alongshore variation in the importance of coastal changes over the study area during a defined time period. More generally, through the presentation of this morphodynamic classification of north Assateague Island, the value of lidar metrics in both examining large lidar data sets for coherent trends and in building hypotheses regarding processes driving barrier evolution is demonstrated

Maryland↗
USGS2003

Tropical Storm Isidore and Hurricane Lili: Louisiana barrier shoreline response, preliminary results

In a cooperative effort between the U.S. Geological Survey, National Aeronautics and Space Administration, University of New Orleans, and Louisiana's Department of Natural Resources, Louisiana's barrier islands were surveyed with airborne topographic lidar and oblique aerialphotography both before and after the impacts of 2002's Tropical Storm Isidore and Hurricane Lili. The surveys were compared to quantify the magnitudes and patterns of erosion and accretion in both natural areas and areas that had been subjected to major restoration. Wave runup exceeded the elevation of the entire Isles Dernieres barrier chain creating overwash deposits that, in places, were driven landward ~ 300 m. This response was not as severe as observed during Hurricane Andrew in 1992 when the Isles Dernieres were completely and continuously inundated and sand bodies were driven landward on the order of 1 km. Based on a comparison of surveys before and after the combined impacts of Lili and Isidore, the largest shoreline change occurred at the east end of East Island and reached ~ 130 m of erosion.

Louisiana↗
USGS2001

Quantifying hurricane-induced coastal changes using topographic lidar

USGS and NASA are investigating the impacts of hurricanes on the United States East and Gulf of Mexico coasts with the ultimate objective of improving predictive capabilities. The cornerstone of our effort is to use topographic lidar to acquire pre- and post-storm topography to quantify changes to beaches and dunes. With its rapidity of acquisition and very high density, lidar is revolutionizing the. quantification of storm-induced coastal change. Lidar surveys have been acquired for the East and Gulf coasts to serve as pre-storm baselines. Within a few days of a hurricane landfall anywhere within the study area, the impacted area will be resurveyed to detect changes. For example, during 1999, Hurricane Dennis impacted the northern North Carolina coast. Along a 70-km length of coast between Cape Hatteras and Oregon Inlet, there was large variability in the types of impacts including overwash, dune erosion, dune stability, and even accretion at the base of dunes. These types of impacts were arranged in coherent patterns that repeated along the coast over scales of tens of kilometers. Preliminary results suggest the variability is related to the influence of offshore shoals that induce longshore gradients in wave energy by wave refraction.

Conference Paper↗