Giacomini Wetland Restoration Project: Restoration: What's the Long-Term Future of the Restored Wetlands?: Sea Level Rise

<-- Page 1. Introduction

Page 3. Precipitation, Run-Off, and Sedimentation -->

 

This map shows the expected extent and duration of tidal inundation under current sea level conditions should the levees and tidegates simply have been removed with no additional earthmoving (i.e., tidal channel creation, ditch filling). Click on this image to download a higher-resolution map (93 KB PDF).

Based on records from the past century, sea level is rising, and sea level rise increases tidal and wave action, which can destabilize wetland and other coastal ecosystems. In 2005, the USGS completed a relative coastal vulnerability study that depicted most of Tomales Bay as having low to moderate vulnerability to sea level rise (Pendleton et al. 2005). NOAA reports that, based on review of historic (1854-1999) water level gauge data, sea level has risen at a rate of 0.00328 to 0.0079 feet/year over the last century and that sea levels have risen 0.007 feet/year in San Francisco since 1906 (NOAA 2001 in KHE 2006). Based on 25 years of Point Reyes water level records, NOAA estimated a current local sea level rise rate in this region of 0.0082 feet/year or, if there were no change in rate, 7.2 inches or 0.6 feet by 2100 (NOAA 2001 in KHE 2006). Based on recent satellite altimetry studies, Cazenave and Narem (2004) report a "very accurate" sea level rise rate of 0.0092 ± 0.0013 feet/year for the 1993-2003 decade, which, if there were no change in rate, would translate to 0.82 feet by 2100. This rate is notably higher than what NOAA's rate of change based on measured changes in tide gauges over the preceding half century (KHE 2006). However, both of these rates are similar to sea level rise rates reported for the California coast as a whole (8 inches/century), which also closely approximated historical global sea level rise rates.

 

This map shows the expected extent and duration of tidal inundation under moderate sea level rise conditions of 0.5 meters, which is based on the average rate of sea level rise estimated by the IPCC model scenarios. This model incorporates levee removal and all other restoration actions. Click on this image to download a higher-resolution map (85 KB PDF).

With the acceleration of climate change impacts, current sea level rise rates are likely to increase, with the exact magnitude of that increase a matter of considerable debate. Earlier this decade, the Intergovernmental Panel on Climate Change (IPCC) developed estimates of sea level rise based on a number of emissions scenarios, with perhaps the most widely accepted rate of rise—at least previously—being 0.5 m (1.65 feet) by 2100. Figure 1 (127 KB PDF) and the map to the right shows what the newly restored Giacomini Wetlands might look were sea level to rise 0.5 m: in this instance, sea level rise would not necessarily convert intertidal vegetated wetland to open water, but could cause a shift "downwards" elevationally in marsh community such that "low" marsh would become more prevalent than "mid" and "high" marsh, and the amount of upland area would decrease. In this case, the potential for upland wetland migration seems eminently feasible, given the relatively large extent of lands not subject to tidal action in the Project Area (~190 acres, with some of this being wet meadow or other seasonal wetland). In general, more than 50 percent of the Marin County coastline has viable area for upland wetland expansion (The Pacific Institute 2009). However, contrasted with that is the situation in many portions of San Francisco Bay where lower elevation wetland directly abuts developed areas, with no undeveloped upland available for wetland migration.

More recently, researchers from University of Arizona, the National Center of Atmospheric Research, and other institutions suggest that accelerated melting of the Arctic and Antarctic ice caps and Greenland glaciers could raise sea level by as much as 3 feet by the end of this century and 13 to 20 feet in coming centuries (Overpeck et al. 2006; Velicogna and Wahr 2006). Cayan et al. (2008) projected that sea level rise rates in California could increase to between 11 and 72 cm (0.4 and 2.4 feet) by 2079-2099. A recent study suggests that even some of these more alarming numbers could be underestimates due to the fact these models—including the IPCC ones—did not incorporate key forces such as gravity and changes in the Earth rotation, leading to potentially another 4 to 5 feet in sea level rise if the West Antarctic Ice Sheet collapses (University of Toronto 2009). In 2009, the Pacific Institute published a report that warned that sea level rise rates in California could climb as high as 1.4 m (4.6 feet) by 2100 (The Pacific Institute 2009). Should sea level rise that high, the report estimated that as much as 41 sq. miles or 26,000 acres of California coastline could be lost due to increases in wave erosion and amplified tides (The Pacific Institute 2009).

<-- Page 1. Introduction

Page 3. Precipitation, Run-Off, and Sedimentation -->

Top of Page

 

What's the Long-Term Future of the Restored Wetlands?
Page 1. Introduction
Page 2. Sea Level Rise
Page 3. Precipitation, Run-Off, and Sedimentation
Page 4. Coastal Winds and Temperature
Page 5. Coastal Fog
Page 6. Coastal Upwelling
Page 7. Acidification of Coastal Waters
Page 8. Changes in Estuarine Salinity with Sea Level Rise
Page 9. Nitrogen Deposition
Page 10. Carbon Sequestration and Interactions of Carbon with Marsh Vegetation Communities
Page 11. Conclusions and References

 

---

restoration includes:

Restoration Water, Water, and More Water How Long Will It Take For Tidal Wetlands To Develop? Two Years Later: Already Dramatic Improvements in Water Quality Giacomini Wetlands: A Haven for Ducks

Spring is in the Air--and in the Water Untangling the Food Web: Changes in Prey Base Following Restoration What's the Long-Term Future of the Restored Wetlands? How Can We Learn About the Restoration? How Can We Be A Part of the Restoration Process? Kids in Wetlands - Learning Through Experience Where Can We View the Restored Wetlands?

---