Posted on May 1st, 2018

Our Changing Landscape – Coastal Erosion of Ocean Beach

In this monthly feature, we span the globe to examine Our Changing Landscape with a time series of medium resolution RapidEye satellite imagery. The RapidEye archive dates back to late 2008 and already contains more than 14 billion square kilometers of data. Last month, we observed wildflowers blooming in the southwest of the United States, and for April we move to the West Coast with a look at coastal erosion of Ocean Beach, California.

Click on the image above to see an animation of 5-meter natural color RapidEye imagery collected over Ocean Beach, California on January 18, 2014, March 26, 2015, June 23, 216 and December 10, 2017. And just like in life, sometimes you win and sometimes you lose – this time we lost unfortunately as the extreme coastal erosion talked about in this article is not visible in the RapidEye images. What we do see is that the level of the ocean seems to be controlled more by the tide and/or size of the waves crashing on the shore. The results of this article make me wonder how effective any satellite imagery would be at determining coastal erosion unless you are using two images in the exact same tidal state with similar wave conditions. (Images Courtesy: © Planet 2018)

The RapidEye Constellation

RapidEye is a constellation of five 5-meter medium resolution satellites each offering five spectral bands of information. The RapidEye constellation offers daily revisits to every location on the planet with a huge footprint that is 77-km wide. The data is priced competitively with a starting cost of $1.28 per square kilometer for all five spectral bands – academics do receive discounts. RapidEye adds a fifth band, the red edge, to the ‘traditional’ multispectral set of blue, green, red and near-infrared (NIR). The additional spectral data in the red edge band allows users to extract more useful land ‘information’ than can be from traditional 4-band imagery sources. When RapidEye imagery is ordered as a Level 3A Orthorectified product, images from multiple dates are extremely well registered, making it the ideal data source for Our Changing Landscape.

Coastal Erosion of Ocean Beach, California

As a non-California native, I (Brock that is) had no idea there were two Ocean Beaches in the state! Today we are focusing on the northern-California Ocean Beach, which is a thin strip of rocky land along the western edge of San Francisco bordered by the Great Highway and the Pacific Ocean. Ocean Beach is known for its frigid temps, knarly waves and sharky waters.

The West Coast of the United States is characterized by two distinct, opposite weather patterns known as El Niño and La Niña. El Niño is defined by above average sea surface warming across the central Equatorial Pacific region and it typically brings warmer-than-average temperatures to the West Coast. While there is no set periodicity to El Niño events, in general they occur during December every two to seven years. The 2015-2016 El Niño felt rather weak to the residents of California, particular Southern California where rainfall was down some 70% versus large El Niño events of the past. However, the 2015-2016 El Niño was one of the most powerful climatic events ever as it stirred up ocean waves to record levels. During December 2015, waves were measured from 26 to 36 feet (7.9 to 11.0 meters) off the coast of California, while typical waves during this season are around 8 feet (or 2.4 meters). These beach smashing waves took their toll on the local landscape, accelerating erosion by some 76% and by some estimates narrowing Ocean Beach by 180 feet (54.9 meters) or more! And when we hear eye popping stats like 180 feet of beach lost in the matter of months, we think to ourselves what a perfect topic for Our Changing Landscape. So it is off to the 5-meter RapidEye archive to check out this erosion in more detail.

If you would like to find out more about using RapidEye for your academic studies, engineering projects or any landscape analysis, let us know at sales@apollomapping.com or (303) 993-3863.

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