BAY DELTA SCIENCE CONFERENCE: Monitoring and Managing Sea-Level Rise Impacts on Tidal Marshes in the San Francisco Estuary

Sonoma Baylands; photo by Scott Hess

Once not all that long ago, the prevailing thought was that if tidal marsh remnants were protected and carefully managed, they would persist for the foreseeable future, providing sanctuary for tidal marsh species that are at-risk due to habitat loss and fragmentation. However, a series of recent independent studies have demonstrated that mature marshes are vulnerable to marsh drowning due to the combination of reduced sediment supply and increased rates of sea-level rise. Furthermore, changing salinity, prolonged droughts, violent storm events, and erosion from extreme flooding add further risk to the viability of these habitats. These insights have prompted additional studies that focus on the dynamics of mature tidal marsh habitats in response to extreme perturbations.

At the 2018 Bay Delta Science Conference, Dr. Michael Vasey, Director, San Francisco Bay National Estuarine Research Reserve, and Associate Director of the Estuary and Ocean Science (EOS) Center at San Francisco State University gave this presentation, noting that it is derived from his work with a collaborative group of people involved with tidal wetland restoration who are thinking about improving the decision making for where future restorations are located, how they are approached, and how they can adapt to changing conditions over time.

He began by noting that the Hamilton Field and Sears Point restorations are the latest generation of tidal wetland restoration projects; they are both large restorations with interesting innovations within a complete marsh approach.  Hamilton Field is about 650 acres, Sears Point is almost 1000 acres, and they are both publicly funded projects; the big difference between them is that the Hamilton Field project is using dredge spoils to raise the elevation while the Sears Point project is utilizing natural sedimentation processes.

There’s a big difference between them, and wouldn’t it be cool to be able to look at these two projects and compare them over reasonable periods of time with common datasets,” he said.  “One is using dredge sediments and the other is using natural sedimentary processes, so what are the differences and how could we evaluate that?  Right now, essentially, that is not happening because each project has approached individually.”

Right now, it’s an interesting period of time, he said.  Over the last 30 years through the Baylands Goals process, 30,000 acres of tidal wetlands are under restoration at a cost of approximately $500 million.  However, one of the biggest issues restoration projects are facing now are the uncertainties associated with climate change.  With the passage of Measure AA in 2016, Bay Area voters approved a $12-per-year parcel tax that will $500 million over 20 years for critical tidal marsh restoration projects around San Francisco Bay.

We’re talking about a major public investment,” said Dr. Vasey.  “We have to do this right.  This is really important.”

We’re looking at extreme changes in sea level rise, which is not only the ocean sea level but the vertical land movement, so there’s a lot of interesting variability out there,” Dr. Vasey said.  “We’re also looking at a reduced sediment supply, so these environmental uncertainties combined with this new responsibility to restore yet another 30,000 acres is really a great opportunity as well as a big challenge.”

However, this next round of tidal wetland restoration is not going to be as easy as it was during the last 20 or 30 years, he said.  “We have big challenges ahead, so we need good science, we need much better knowledge of what’s going on and a way of comparing what’s going on overtime so we can use that information effectively.”

One of the basic serious problems is the result of the Clean Water Act and 404 permits which requires mitigation for loss of wetlands and permits are based on the mitigation requirements, including monitoring; this means monitoring is most often tied to the permitting, he pointed out.

One of the earliest big publicly driven tidal wetland projects was in conjunction with construction of the Golden Gate Ferry; the project removed a patch of tidal wetland and as mitigation, they restored a back levee area called Muzzy Marsh.  It was a small project, but one of the first to really use dredged sediments to try and gain some elevation capital, he said.

This is way things worked up to the present, basically, and this project by project condition for permits, I would argue is one of the big problems we have right now.”

The legacy of project-by-project monitoring is that most of the funds end up going into the planning and the permitting and construction, and by the time that’s all done, funds are limited at that point to conduct the monitoring.  Monitoring is perceived as a required ‘add-on’ to already stretched budgets, and different requirements are negotiated with the permitting agencies, which leads to costs being minimized by unrealistic time frames for monitoring tidal marsh evolution, he noted.

This is a problem because the pressure on the agencies that are providing these permits to be reasonable and to fit the monitoring in and to sort of scale it back to the minimum to some degree,” he said.  “I’m not saying that they haven’t done a very good job of this, but there are different agencies involved in permitting the same project and it becomes a problem in terms of how far you are able to squeeze the project proponents.”

Ultimately, a lot of data is acquired over time, but all that data just sits there, he said.  “Nobody is really analyzing it and looking at it in a comparative manner and getting that information back to the decision makers who are really working on the whole enterprise of restoring tidal wetlands in the estuary,” said Dr. Vasey.  “Ultimately, it means that people think monitoring is just not worthwhile.  It’s just not worth the funding and basically even though we learn anecdotally from it or we learn to some degree from it, we don’t really learn strategically, we don’t really learn comprehensively, and we’re just not taking advantage of this long-term experiment in the public interest to try to rebuild resilience in these really wonderful tidal wetland ecosystems that we have in this region.”

The Sonoma Baylands was one of the early dredge sediment sites, and it’s taken a very, long time.  “We did have a few problems with how the hydrology worked on that site, but now we have a really excellent spartina meadow system,” he said.  “But this pickleweed here is the annual pickleweed; it’s not the perennial pickleweed.  We do not have enough elevation there yet to support perennial pickleweed high marsh environments and this is 20+ years.  So it takes time.  And maybe we could have learned a few things from this project.  It is being monitored but it’s not necessarily being shared with the broader community because we just don’t have the mechanism to do that.”

The antithesis to this problem is the Salt Pond Restoration Project, which embedded adaptive management in the project.  “They’ve done some brilliant work in terms of adaptive management, and parenthetically people like me up in the South Bay and Suisun have learned a little bit about it over time,“ he said.  “This is the model for the adaptive management where you have your reference conditions, and whatever the metric is, if it goes below a certain threshold that targets you to begin some corrective action.”

There are two fundamental problems, Dr. Vasey said.  One is that how do you sustain funding for this over time?  Unfortunately for the Salt Pond Restoration Project, it’s hard to sustain funding.  “We need a sustainable funding mechanism for monitoring tidal wetlands in the region,” he said.  “And it has to be collaborative.”

The second problem is the assumption of target reference conditions, because the model predictions for tidal wetlands in the estuary project is that they will convert to mudflats under high sea level, low sediment supply scenarios.  “We have to be tracking what’s happening with these systems and we can’t be necessarily thinking that the restored systems that we have are necessarily going to reach those target conditions because we have external environmental changes going on and so we really have to monitor both.”

At the National Estuarine Research Reserve site at China Camp, they are monitoring this carefully, although some places can be monitored a little more strategically, he said.

There is a project to develop a Wetland Regional Monitoring Program that is being funded by Region 9 of the EPA.  He said it is something people have wanted for some time, but now with the environmental uncertainties and the commitment of local public funding for restoration, the opportunity is now, so they will be working on it for the next year and a half.

It’s a very inclusive process which is very exciting,” Dr. Vasey said.  “It has the regulatory agencies and the land managers – all the parties at the table.  It’s well organized and they are driving it hard.  The whole purpose of it is to be scientifically credible, cost-effective, and financially sustainable, emphasizing multiple partners and really providing long-term data analyses reports that inform wetland decision making.”

And lastly, we need to use new innovations in remote sensing to track large restoration projects in a coordinated manner.  The slide illustrates how in this three-year period of time, natural sedimentation processes have basically raised the level of mud roughly 1 meter in three years.

That’s a lot of sediment in a 1000 acres of wetlands, so it’s pretty phenomenal how that natural sedimentation process has functioned in a particular way,” he said.  “It’s not going to happen everywhere, but there are sweet spots around the Bay where natural sedimentation processes may well be a more effective solution than trying something like dredge sediments, for example.”

From the perspective of regional monitoring, we realize we can’t do fine scale monitoring everywhere, but we need to do fine scale monitoring at least at certain particular places so that we can track change on more of an annual basis, he said.  The reserve sites are sentinel sites; there is a national program which is focused on measuring marsh accretion and sediment transport, as well as vegetation surveys every year at a very fine scale.  “We’re hoping that is going to inform what’s happening at sort of these subbasin scales,” he said.  “We may need more over time, but at least we’re going to start with those.”

They will be using remote sensing data, quantitative sampling, and a rapid assessment and bringing it all together to figure out how to look at things that are happening at the regional scale.  They have had several workshops on a variety of topics such as physical processes, vegetation, and wildlife response.  They will be having a workshop to look at the extent restoration might actually constitute a human health problem from mosquitoes.

At a recent workshop, NOAA sent out two individuals from the National Geodetic Survey, who are taking this project very seriously.  “I could never get them out to look at my little reserve components, but bringing them out to look at the San Francisco Estuary, that’s a different deal,” said Dr. Vasey.  “Moving in a regional process, we have the chance to attract a lot more attention and a lot more funding from outside sources than just within our own — and a lot more information, too.”

At a recent visit to the Sears Point restoration, Dr. Vasey saw pawprints from river otters.  “We’ve already seen a lot of river otter activity out a Sears Point,” he said.  “With these restorations, it’s going to take time to get there, and along the way, there’s a whole lot of utilization of these sites by a lot of different species, fish, mammals, invertebrates, and plants.  What we’ve really got out there is this kind of landscape of shifting types of marshes in the making, and marshes that have become, and all of that process is really contributing to the health of the ecology of the estuary.”

Dr. Vasey concluded by thanking his colleagues who have contributed to this work.

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