Sand Mining Impacts on Long-Term Dune Erosion in Southern Monterey Bay
NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
Pagination or Media Count:
Southern Monterey Bay was the most intensively mined shoreline with sand removed directly from the surf zone in the U.S. during the period from 1906 until 1990, when the mines were closed following hypotheses that the mining caused coastal erosion It is estimated that the yearly averaged amount of mined sand between 1940 and 1984 was 128,000 m3yr, which is approximately 50 of the yearly average dune volume loss during this period. To assess the impact of sand mining, erosion rates along an 18km range of shoreline during the times of intensive sand mining 1940-2004. Most of the shoreline is composed of unconsolidated sand with extensive sand dunes rising up to a height of 46 m, vulnerable to the erosive forces of storm waves. Erosion is defined here as a recession of the top edge of the dune. Recession was determined using stereo-photogrammetry, and LIDAR and OPS surveys. Long-term erosion rates vary from about 0.5 my in the middle of the range, and then decrease northward. Erosion events are episodic and occur when storm waves and high tides coincide, allowing swath to undercut the dune and resulting in permanent recession. Erosion appears to be correlated with the occurrence of El Ninos. The calculated volume lots of the dune in southern Monterey Bay during the 1997-98 El Nino winter was 1,820,000 m3yr. After cessation of sand mining in 1990, the erosion rates decreased at locations in the southern end of the bay but have not significantly changed at other locations.
- Physical and Dynamic Oceanography
- Mining Engineering