scholarly journals RECESSION OF MARINE TERRACES - WITH SPECIAL REFERENCE TO THE COASTAL AREA NORTH OF SANTA CRUZ, CALIFORNIA

1968 ◽  
Vol 1 (11) ◽  
pp. 42
Author(s):  
Robert M. Sorenson
Keyword(s):  
Sea Level ◽  
Wave Climate ◽  
Army Corps ◽  
Ocean Bottom ◽  
Army Corps Of Engineers ◽  
Santa Cruz ◽  
Marine Terraces ◽  
History Of ◽  
Recession Rates ◽  
Area North

The concept "wave base" (or "surf base"), i.e. the maximum depth below mean sea level at which shoaling waves will effectively erode the ocean bottom leading to the recession of a shoreline, is discussed. Also, past and present opinions as to the magnitude of wave base in general and specifically in the area near Santa Cruz, California, and the variables controlling this phenomenon are presented. Then, an account of the author's successful and unsuccessful attempts to determine average rates of cliff retreat in the study area is presented along with the specific cliff recession rates obtained. These compare favorably with the recession rates measured by the U. S. Army Corps of Engineers for nearby areas of similar geology and topography and with rates determined for similar coastal areas in various parts of the world. A brief discussion of the spectrum of cliff recession rates found m areas of varying geology and wave climate is also presented. The accepted history of sea level since the last glacial maximum, particularly during the last 7,000 years, is reviewed as well as pertinent information on the geology, topography and wave climate of the study area. It is then shown that average recession rates estimated by relating extrapolated bedrock profiles of the lowest marine terraces with the accepted history of the latest sea level rise compare favorably with the recently measured recession rates. However, a conflict exists between the present wave-cut terrace profiles, the accepted history of sea level and the accepted value of wave base.

Discovering the Polaris Fault, Martis Creek Dam, Truckee, California

2018 ◽  
Vol 24 (1) ◽  
pp. 111-120
Author(s):  
Lewis E. Hunter ◽  
Ronn S. Rose ◽  
Bruce Hilton ◽  
William McCormick ◽  
Todd Crampton
Keyword(s):  
Flood Control ◽  
Late Quaternary ◽  
Ground Surface ◽  
Lake Tahoe ◽  
The United States ◽  
Army Corps ◽  
Army Corps Of Engineers ◽  
Vegetation Canopy ◽  
History Of ◽  
Control Purpose

Abstract Martis Creek Dam, located in the Truckee Basin north of Lake Tahoe, CA, was initially rated as one of the U.S. Army Corps of Engineers’ highest risk dams in the United States. While the dam has performed its flood control purpose, a history of excessive seepage during even moderate reservoir levels has prevented it from also fulfilling its potential water storage function. During seepage and seismic studies to assess and mitigate deficiencies, high-resolution light detection and ranging (LiDAR) data were obtained. This imagery provides an unprecedented representation of the ground surface that allows evaluation of geomorphology even in areas with a dense vegetation canopy. At Martis Creek Dam, this geomorphic analysis resulted in the recognition of a previously unknown and through-going lineament between the spillway and dam embankment. This feature extends to the southeast, where several lineament splays are exposed on the East Martis Creek Fan. These lineaments were subsequently explored by paleo-seismic trenching at two locations and confirmed as faults with Late Quaternary to Holocene displacement. Faulting was confirmed in both trenches as unique splays of a fault zone with several feet of apparent normal (vertical) slip and an unknown magnitude, but a potentially significant, strike-slip component. Faulting was observed near the ground surface in both cases, and multiple fault events (a minimum of two) are interpreted as at least latest Pleistocene in age, and probably active in the Holocene.

Rocky shores and development of the Pliocene-Pleistocene Arroyo Blanco Basin on Isla Carmen in the Gulf of California, Mexico

2006 ◽  
Vol 43 (8) ◽  
pp. 1149-1164 ◽  
Author(s):  
James M Eros ◽  
Markes E Johnson ◽  
David H Backus
Keyword(s):  
Sea Level ◽  
Gulf Of California ◽  
Rocky Shore ◽  
Normal Faults ◽  
Rocky Shores ◽  
Last Interglacial ◽  
Marine Terraces ◽  
Shell Beds ◽  
History Of ◽  
Cap Rock

Arroyo Blanco Basin on Isla Carmen preserves a 157 m thick, nearly complete record of Pliocene–Pleistocene history in the Gulf of California. Examples of rocky-shore geomorphology occur on all margins of this trapezoidal-shaped, 3.3 km2 basin. A shoreline is developed in low relief on Miocene andesite from the Comondú Group at the rear of the basin parallel to the long axis of the island. Two end walls trace normal faults that stayed active during the life of the basin and maintained steep rocky shores. The basin is 64% filled by calcarudite and calcarenite derived from crushed rhodolith debris. Other facies include shell beds and stringers of andesite conglomerate that define a 4°–6° ramp. The ramp expanded onshore through Pliocene time, based on a succession of overlapping range zones for 22 macrofossils typical of Lower through Upper Pliocene strata in the Gulf of California. The unconformity exposed 1 km inland at the rear of the basin is between Miocene volcanics and Pleistocene cap rock at an elevation of 170 m above sea level. Whole rhodoliths encrusted on andesite pebbles occur above this unconformity. Presumably, the older Miocene-Pliocene unconformity is buried beneath the ramp. Four marine terraces with sea cliffs notched in Pliocene limestone occur at elevations of 68, 58, 37, and 12 m. The 12 m terrace is associated regionally with the last interglacial epoch between 120 000 and 135 000 years ago. Juxtaposition of ramp and terrace features in the same exhumed basin supports a long history of gradual Pliocene subsidence followed by episodic Pleistocene uplift.

scholarly journals UNMANNED AERIAL SYSTEM LIDAR SURVEY OF TWO BREAKWATERS IN THE HAWAIIAN ISLANDS

2018 ◽  
pp. 23
Author(s):  
Jessica H. Podoski ◽  
Thomas D. Smith ◽  
David C. Finnegan ◽  
Adam L. LeWinter ◽  
Peter J. Gadomski
Keyword(s):  
Spatial Data ◽  
Wave Climate ◽  
Remote Sensing And Gis ◽  
Light Detection And Ranging ◽  
Army Corps ◽  
Army Corps Of Engineers ◽  
Operation And Maintenance ◽  
Center Of Expertise ◽  
Ocean Wave Climate ◽  
The U.S

The U.S. Army Corps of Engineers (USACE), Honolulu District (POH) is responsible for the operation and maintenance of 26 navigation projects within the State of Hawaii and the U.S. Pacific territories. The majority of these deep-draft and small-boat harbors include breakwaters that are consistently exposed to a substantial and varied Pacific Ocean wave climate, requiring POH to maintain a rigorous structure condition inspection program to ensure safe and efficient operations at all of its navigation projects. As part of its constant efforts to improve the quality and efficiency of this inspection program, POH has joined with the USACE Cold Regions Research and Engineering Laboratory (CRREL) Remote Sensing and GIS Center of Expertise to utilize an Unmanned LiDAR Scanning (ULS) system to collect LiDAR (Light Detection and Ranging) spatial data and co-registered imagery of breakwaters at Hilo Deep Draft Harbor on the island of Hawaii, and Kaumalapau Deep Draft Harbor on the island of Lanai.

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