California Coast & Ocean

I am looking at a map. It is large, several feet by several feet, and hangs on the wall of the office of Rikk Kvitek, a professor of science and environmental policy at Cal State University Monterey Bay and director of CSUMB’s Seafloor Mapping Laboratory. Vibrantly hued, the map depicts Elkhorn Slough, a vital 70-square-mile wetland and watershed on the central coast. The colors represent various land uses and habitat types—natural oak woodland, acres of pickleweed, ranchland, agricultural fields, the built-up areas of Moss Landing at the slough’s mouth, the Duke Energy power plant. The depiction is more or less realistic: you can almost see the dips of land into shaded valleys; the rise into pine groves where, each spring, great egrets and blue herons raucously nest.

More remarkable than the depiction of the land, however, is what the map shows of water features: the main channel and dendritic fingers of the slough itself, the basin of Moss Landing harbor, the nearshore waters that, for the most part, gently slope away from the land—but then there’s the slash of the Monterey Submarine Canyon, wending its way quickly to great depths.

These features don’t show up as the plain blue of most maps—the water as seen from land, a flat surface that hides whatever smooth, bumpy, or convoluted surfaces might lie beneath. Instead, the subsurface land—the muddy bottom, sandy seafloor, rocky reefs—is depicted in all its glory. Although it’s covered with water, the land down there is just as rich and interesting as the land up here.

And now we have the technology to depict it. It is as if a set of golden gates has been unlocked and swung open, allowing access to a realm hitherto accessible only in bits and pieces to a select few who made the extra effort, with plumb lines, wetsuits, and active imaginations.

The capacity to use maps as powerful predictive tools is a real boon in the contentious, real-world business of setting aside habitat for protection of dwindling species. Just as significantly, the fact that maps can serve as accurate, and meaningful, pictures of the undersea landscape will allow Marine Protected Area advocates to present nonscientists with something they can easily relate to. Both these qualities of the modern “map” will no doubt change the way we use and view our nearshore natural resources. It is no longer possible to say, “But we don’t really know what’s down there.” We know more and more all the time, and we can show what we know in a highly scientific yet intuitively understandable way.

“I find it just stunningly beautiful to look at some of these images,” says Kvitek, “especially when you lay them out in big sheets showing the habitat. People are taken aback by what’s out there. It’s been invisible.”

This article is greatly abridged. For the full text, see the print edition of Coast & Ocean.

Spatial extent and examples of seafloor mapping data sets (multibeam bathymetry and sidescan sonar) available to the MLPA Initiative for state waters along the Central California Coast, compiled by Carrie Bretz & Rikk Kvitek, Seafloor Mapping Lab, California State University, Monterey Bay. http://seafloor.csumb.edu

Figure 1. Extent of marine habitat mapping data along the Central California Coast. Data sets represented include those from various state and federal agencies, educational institutions and private companies willing and able to share information. Most modern multibeam sonar systems produce both multibeam bathymetry and sidescan sonar data, so where multibeam surveys are shown on the following chart, sidescan data also exist. Where sidescan surveys are shown, only sidescan data are available.

The following figures illustrate the differences in the types of seafloor mapping data available along the California coast.

Figure 2. Yankee Point area along the Big Sur coast as depicted on NOAA nautical chart showing depth contours and bathymetric soundings. This image is representative of the type of seafloor habitat data available for the majority of California State Waters.

Figure 3.  High-resolution DEM (digital elevation model) in shaded relief of the seafloor at Yankee Point created using multibeam sonar. Rocky relief and soft sediment habitats are easily discernible, and can be quickly and accurately classified into habitat types using automated computer programs. DEM’s created at different times of the same area can be subtracted from each other to precisely quantify environmental change (e.g. sediment transport, erosion and burial).

Figure 4. A sidescan sonar image of the Yankee Point area, in which different bottom types (sand, gravel, rock) appear as various shades of gray.