Project to help predict hazards from tropical cyclones in the Southwest(U.S.)and Mexico
U.S. Senator Harry Reid announced today that DRI’s Jose Luis Antinao, Ph.D. was awarded a $266,000 grant from the National Science Foundation (NSF) to the study the effects of tropical cyclones (hurricanes) in Baja California, and Mexico.
The purpose of this project is to improve hazard characterization of these potentially large storms and their effects on desert ecosystems, especially geologic processes related to flooding of desert basins. This project is a collaborative effort with UCLA researcher Edward Rhodes, who also was awarded $150,000 to support geologic dating of sediments for this study.
Antinao, a postdoctoral fellow from Chile, working with DRI Research Professor Eric McDonald, is using alluvial fans (large fan-shaped deposits of boulders and gravel common to desert valleys formed when flood waters exit mountain canyons) to better understand the effects of potentially high rainfall in desert regions. These enormous storms frequently occur off the western coasts of Mexico from August through November and historically have generated several days of very intense rainfall in the southwestern U.S. For example, Hurricane Kathleen, a tropical cyclone of the 1976, caused widespread flooding and damage in Baja and parts of the southwestern United States.
Recent research examining how alluvial fan deposits are created indicates that extremely large storms may be required to cause wide-spread flooding and the wide-spread formation of alluvial fans across desert valleys and that the occurrence of these large storm events may be more common than previously thought.
The two scientists are currently studying the history of alluvial fans and collecting samples near Laz Paz and San Jose del Cabo, Baja California Sur, a region where alluvial fans appear to be the result of massive flooding from high rainfall of tropical storms. They want to develop a chronology of the alluvial fans in this region as a record of large-scale flooding, alluvial fan formation, and climate history over the last 100 to 100,000 years.
Alluvial fans are a primary geologic feature of deserts and many of the most populous areas in the southwestern region of North America are built across these regionally extensive deposits. Understanding the history of alluvial fans has direct importance to predicting the impact of desert flooding on urban centers, critical infrastructure such as bridges and pipelines that cross desert fans and washes, and calculating seismic hazards.
The results of this study will give McDonald and Antinao a clear picture of when the alluvial units were built, when the alluvial surfaces stabilized, how fast sediment was deposited, and how long the sediment was stored in the hill slopes before transport and deposition.
“Alluvial fans require frequent flooding to develop and increase in size, so by looking at the soil and sediment properties of alluvial fans in southern Baja we will develop a timeline of tropical storm and flooding frequency, periods of region-wide sediment deposition, and potentially link the longer-term history of alluvial fans with recognized periods of major climate changes characterized by a greater occurrence of moisture and rainfall in the American deserts,” McDonald said.
In addition to providing a better understanding of cyclone effects and recurrence, the research will add critical data for a more precise correlation and geologic dating of alluvial fan surfaces across both the U.S. and Mexico. That timeline is crucial in helping researchers better understand climate change, earthquake, and flood histories.
“The study will increase our understanding of fault kinematics not only in neighboring areas in Baja California but also in all arid southwestern North America and other regions where alluvial surfaces are used to infer earthquake recurrence rates,” Antinao said.
The project is titled “Collaborative Research: Tropical cyclone imprint on late Quaternary alluvial fans of Baja California: Key for understanding arid regions landscape evolution.” Besides collaboration with UCLA, Antinao and McDonald are working with colleagues at CICESE, a Mexican Research Institute based in Ensenada, which in 2010 signed a collaboration agreement to perform joint research with DRI.