Geology topics

Joseph Long

Publications and source records attributed to Joseph Long.

3 recordsLinked to original sources

USGS2019

Forecasts of coastal change hazards

Model predictions of severe storm impacts provide coastal residents, emergency managers, and partner organizations valuable predictive information for planning and response to extreme storm events. The foundation of this work is a USGS-developed numerical model to forecast storm-induced coastal water levels and expected coastal change, including dune erosion, overwash, and inundation. The model is operated in three modes: generalized scenarios, real-time storms, and an operational forecast, with each mode requiring slightly different water level inputs. To evaluate and improve the accuracy of the models, we collect data on water levels and coastal change. In particular, observations before, after, and during storm conditions are used to test the different model applications. Forecast validation for Hurricanes Matthew (2016) and Irma (2017) illustrate three cases with demonstrated forecast skill and three cases with poor skill, and reveal elements of the modeling and/or testing approach which require improvement.

Conference Paper↗

USGS2012

Extended Kalman Filter framework for forecasting shoreline evolution

A shoreline change model incorporating both long- and short-term evolution is integrated into a data assimilation framework that uses sparse observations to generate an updated forecast of shoreline position and to estimate unobserved geophysical variables and model parameters. Application of the assimilation algorithm provides quantitative statistical estimates of combined model-data forecast uncertainty which is crucial for developing hazard vulnerability assessments, evaluation of prediction skill, and identifying future data collection needs. Significant attention is given to the estimation of four non-observable parameter values and separating two scales of shoreline evolution using only one observable morphological quantity (i.e. shoreline position).

Geophysical Research Letters↗

USGS1964

Barchan-dune movement in Imperial Valley, California

The movement of 47 barchan dunes on the west side of Salton Sea, California, ranged from 325 to 925 feet over the 7 years between 1956 and 1963, an average of 82 feet per year. During the 15 years between 1941 and 1956, the movement of 34 of these dunes ranged between 350 and 1200 feet, an average of 50 feet per year. This difference in average movement during the two intervals is attributed primarily to increased sand supply. Movement ( D ) plotted against height of slip face ( H ) for the Salton dunes fits reasonably well with Finkel's reciprocal curve (1 /D = n + k H ) or with a law of the type D = Pe rH . Factors other than height affect the rate of movement, one of the more important being the state of the dune, whether growing or steady state. Barchan shape, whether fat or slim, may also influence the rate of movement of growing dunes. None of these dunes needs be more than 300 years old.

California↗