All Hail The King… Tides, That Is

If you’ve been watching the news, you’ve probably heard some mention of King Tides in places like Sausalito, Mill Valley, San Francisco, and Alameda. A King Tide is no farcical aquatic ceremony, but it is one of the highest high tides of the year. A King Tide is a natural phenomenon that occurs near the Summer and Winter solstices, during the new and full moon phases, when the moon, sun, and Earth are aligned. This alignment causes the strongest biannual gravitational force on Earth’s oceans, resulting in these dramatic tidal fluctuations.

Figure 1. Earth’s tides and the contributing gravitational factors
Figure 1. Earth’s tides and the contributing gravitational factors.

King Tides help us to see today what will be the average daily high tides in 2050 and they show us now where flooding will occur as the sea level continues to rise as shown in the photos below. These photos were submitted to the California King Tides Project, which encourages people to take pictures of their communities to document flooding during King Tides.

Photos a-f. Photos submitted to the California King Tides Project of San Francisco Bay Area communities during a King Tide in Winter 2012/2013. (a) The Embarcadero in San Francisco (b) Sidewalk in Alameda (c) HWY 1 underpass in Sausalito (d) Byway in Mill Valley (e) Sharp Park in Pacifica, (f) Rockaway in Pacifica
Photos a-f. Photos submitted to the California King Tides Project of San Francisco Bay Area communities during a King Tide in Winter 2012/2013. (a) The Embarcadero in San Francisco (b) Sidewalk in Alameda (c) HWY 1 underpass in Sausalito (d) Byway in Mill Valley (e) Sharp Park in Pacifica, (f) Rockaway in Pacifica

Tide gauge measurements can tell us about past and present sea levels —  The sea level in San Francisco Bay has risen about 4 inches since the year 2000. Based on these measurements and more precise climate modeling, scientists can now predict with strong confidence that the Bay Area will see an additional 10 inches of sea level rise by 2050. Beyond 2050, scientists expect sea levels to rise much faster than the current rate, partly because of positive feedback loops associated with global ice melt. Even the most conservative estimates suggest sea levels will rise a minimum of 40 inches by 2100 and as much as 16 feet if the global ice continues to melt faster than previously estimated.

So, what does sea level rise mean for the Bay Area and the people who live here?

San Francisco Bay is one of the most urbanized estuaries in the world. The majority of our seven million Bay Area residents live and work within a half mile from the Bay. We’ve filled in over 80% of the wetlands that once ringed the Bay and built our communities right at the edge of a bay that is expanding faster every day. We can look to King Tide events to show us the areas of this urbanized coastline that will be at risk in the near future.

As I mentioned, King Tides already bring higher sea levels into our coastal communities and flood urban infrastructure, reaching highways and roads in several areas throughout our region, including San Francisco, Marin, Alameda, and San Mateo counties. What I find of particular interest in the images above are the clear skies, demonstrating that the streets are flooded from ocean tides, not rainfall. However, add rainfall and tidal action and these “interesting” images can become downright devastating. The water you see on the pavement and in the streets during the King Tides indicate where the sea level was at that moment in those areas and we can expect to see that sea level every day in 2050 or even earlier. Combining those extreme high tides with large storms could result in devastating impacts, as you can see in the last two images.

Transition zones and rising tides

The Bay has expanded and contracted several times throughout history, but early humans hadn’t established permanent structures at the edges so the wetlands and the people that relied on them were able to migrate inland. Ten thousand years ago, sea levels were rising so quickly that every generation of early humans living along the coast or Bay was probably forced to retreat inland. Wetlands historically transitioned from low tidal marsh to upland terrestrial habitat across areas that spanned a mile or more. Today, most of our existing wetlands are squeezed up against urban infrastructure with narrow or no transition zones so these wetlands have nowhere to migrate. Healthy wetlands act as a sponge, slowing down and soaking up large volumes of water, so healthy wetlands help to keep coastal communities safe by buffering the effects of severe storms and flooding. With narrow transition zones and no migration space, our urban coastal tidal wetlands will drown as the sea continues to rise and will no longer provide the services we need unless we plan ahead.

In 1999, over 100 scientists, managers, and urban planners published the Baylands Goals Report, which became the basis for wetland restoration in the Bay Area and identified the need to conserve and restore 100,000 acres of healthy wetland habitat to provide healthy wetland ecosystems in the Bay Area. In October 2015, more than 200 scientists, natural resource managers, and urban planners published an update to the Baylands Goals report to include recommendations based on climate change. The Baylands Goals Science update includes an entire chapter dedicated to identifying types of transition zones and defining their services while emphasizing the need to accelerate restoration of these important areas of transition. For more information on the science update to the Baylands Goals Report, check out our Habitat Restoration Director’s blog, Baylands and Climate Change and to learn more about the general benefits of transition zones, check out my blog, What is Life without Transition?.

The solutions to climate change challenges are complex, but rising to the top of the list of challenges is the issue of big funding needs. Save The Bay is excited to be working on an important measure to invest critical funding in restoration projects. We are working with the Bay Restoration Authority to place a $12 parcel tax on the ballot throughout the nine-county Bay Area which will produce about half a billion dollars for Bay restoration over the next 20 years.

Communities can help to prepare for sea level rise by becoming involved with and supporting tidal wetland conservation and restoration. So it goes – wide, healthy wetlands between the Bay and urban infrastructure help to keep coastal communities safe from sea level rise.

If you fancy taking pictures and want to help document areas at risk for flooding as sea level rise, use this map to plan your shoot times and locations to photograph the high water in your community this King Tide season and submit your photos to the California King Tides Project.