In the Bay Area, preparing for climate change impacts is one of several drivers leading flood protection agencies to pursue nature-based flood management practices. As agencies prepare to replace aging infrastructure, the next generation of flood protection can be designed to dampen the impacts of climate change, increase ecosystem resilience, and contribute to groundwater recharge.
At the State of the San Francisco Estuary conference last fall, Robin Grossinger, Senior Scientist for the San Francisco Estuary Institute, gave a presentation on the Landscape Resilience Framework, a project to provide a framework for systematically thinking about the many elements involved in integrated flood control projects.
He began by posing the question, how do we make our systems more resilient? “Anticipating climate change, all the stresses we’re already dealing with, how do we make our ecosystems, our natural systems, and also our infrastructure that is intertwined with these systems, how do they adjust and accommodate to climate change and how do we improve that?” he said.
He started by defining what resiliency to an ecosystem means. “It’s basically the idea that a system’s functions that we care about – it could be number of salmon in the stream or riparian trees, it could be flood protection – and that service, it goes down and up a little bit. It might get hit by an event like a drought or flood, but if it’s resilient, the function persists. It doesn’t mean it doesn’t change through time, and adapt and evolve, but it maintains itself. When a big event of some kind, such as a drought or a flood or a fire, the system can crash or it can pull itself together and persist as a version of semblance of that system.”
There are drivers that are global phenomena that have impacts on our systems, but we can’t really control them locally, he said. “But there are a lot of steps in between that driver that is essentially given to us and the impact, and so what we do can amplify or we can dampen the impact,” he said. “The energy is going into the system, and we can either multiply it or increase it, or we can actually decrease it through these steps between the driver and the impact. We can have a major rainfall event, and we’re not going to control how much it rains, but what we do, I argue, will largely determine whether it is catastrophic flood or whether it’s just a big flow that stays in the channel.”
We can make our landscapes more resilient. “By looking at those arrows or those steps and seeing what we can do to affect the translation of those massive climatic drivers into system impacts, we can make our landscapes more resilient, and what we do is going to either amplify or dampen climate effects.”
Integrated approaches are the great challenge, but also the best hope. “Those solutions are going to need to be really integrated, like linking sediment and flood, how we manage water, stormwater, land use – that’s a really enormous challenge, just the way our systems are set up, but that is how we’re going to get the best results.”
A systematic framework can help. “It’s the way we create resilient landscapes, and resilient in the broadest sense too that people want to support them, people want to pay for them, they are not stopped be regulatory processes, and we think that a systematic framework can help.”
He said that in trying to apply reliance thinking, it’s a bit of a ‘hodgepodge’ of potential actions that could be taken, so a more systematic way to think through the elements that are needed to make systems more resilient and make sure they have them all, as those elements cross many disciplines and scale.
The San Francisco Estuary Institute recently developed the Landscape Resilience Framework that was developed with the guidance of a team of international and regional experts as well as local stakeholders. Click here to download a copy of the Landscape Resilience Framework.
Mr. Grossinger then gave some highlights of the framework. “The Landscape Resilience Framework has seven major principles, and each one has three or four subprinciples or tenets, and it’s a systematic way that we can think about systems in a more dynamic, less static way,” he said. “We’re thinking about processes that support the systems and the functions we want to have, thinking about the scale we need to be working at, thinking about connectivity, thinking about diversity and complexity – that’s the portfolio effect that we want to have so impacts aren’t translated the same way on all the different parts of our system – all the different ways we think about resilience. It’s actually in a lot of the ways, the we think about resilience in our life with investments, diversification, shock absorbers or buffers – all the things we try to build into our lives, we need those in our landscapes, and they come from a lot of different dimensions.”
They worked with the experts and stakeholders to develop visions and strategies for resilient landscapes that they could then work towards through different projects and programs. “A few examples we’ve been working on is Flood Control 2.0, a vision that integrates flood protection and tidal marsh resilience to try to increase both of those through an integrated approach,” he said. “We’re working with Mike Connor and EBDA, thinking about treated wastewater and Baylands resilience and how do those integrate so we’re making more functional systems at the edge involving the water coming out of our systems. We’re working in the Delta to develop regional strategies, and we’re working more on urban redesign with Google and others including Santa Clara Valley Water District in the South Bay.”
There are flood protection challenges ahead, Mr. Grossinger pointed out. “There’s the probability of more intense unpredictable storms meaning we have to size bigger just partly for the uncertainty as well as what we know,” he said. “In the snowmelt systems, there is this huge change as the greater proportion of precipitation falls as rain, and then the greater recognition that much bigger events than what we’ve seen in the past few decades are probable, atmospheric river type events – really big storms.”
“Talking to flood managers and flood district staff, there’s are all of these other things that are equally are challenging: aging infrastructure, increasing challenges with environmental permitting, less federal funding to rely on, and low public awareness of the risk and the need for flood protection funding – because it’s been pretty effective in the last few decades,” he said. “So all these together make it potentially difficult in maintaining the level of protection that has been achieved, as well as some problem areas that still exist, but really looking towards the future and seeing there’s going to be a lot of work needed, and all of this together contributes to the larger sense of resilience or conversely vulnerability of these systems.”
He then presented a graphic that depicts the different dimensions of resilience. “I think most of the time, people are talking about social resilience or socio-economic resilience, but we at SFEI largely think about ecological resilience – how do we help our ecosystems adapt and continue to thrive, or infrastructure resilience such as the flood protection system, and then there are all these other elements that contribute to overall resilience of a community or a region,” he said. “But the area that we’re largely focusing on at this conference is the overlap between the ecological and the infrastructure. I don’t know why they called it ‘engineering resilience’ … in my mind, that’s green infrastructure.”
“The area of overlap is where there’s a lot of opportunity to make our systems more resilient for a variety of reasons, but that’s the sweet spot where a lot of things are going to work and be successful in terms of funding, in terms of permitting, and in terms of actually being resilient for ecosystems and infrastructure,” Mr. Grossinger said.
He then gave two examples.
Example 1: Green infrastructure that supports or mimics natural processes
The resilience framework has a long list of actions needed for Bay Area streams, the principle of infrastructure mimicking natural processes is a fundamental change that would make our systems more resilient, Mr. Grossinger said. He gave an example from a project that the LID group at SFEI is currently monitoring at the San Francisco State University campus that collects runoff and directs it to a series of rain gardens.
He pointed out the rainfall event, noting that there had been three inches of rain the previous four days, so presumably things are pretty saturated. “That’s a fair amount of rain in a four day period,” he said. “The bars are the water coming into this series of rain gardens, and they pretty much track the rainfall, they are directly reflecting what happens. Here is the peak rainfall coming from all these hard impervious surfaces, and here’s what’s actually going out in the blue – nothing. For most of this whole storm series, and even when the storm peaks, half of what is actually coming in, so this is reducing the flood peaks, this is acting as a dampener, it’s reducing the effect of this event.”
They are working on another project funded by EPA, the San Francisco Estuary Partnership, the City of San Jose, and others looking at the sub-watershed scales and how would you get 30% runoff reduction. “The reduction of mercury and PCB loads to the bay is actually the driver for this study, but they also looked at how that affected runoff, and in a 2 year storm, the modeling suggested it reduced the peak flow by 44%, so that’s a pretty remarkable reduction. You even get a bit of groundwater recharge benefit, not huge, it’s about 5% as there are clay soils in this part of the valley, but I think it would be much more in other parts of the valley.”
It’s an example of how you can have a big event, but have a better outcome because you’ve modulated things, he said. “If we look at what this arrow is, precipitation goes through all of this simplified flowchart to get to the impacts. Precipitation has to turn into runoff, it has to turn into peak flow, and these kinds of things lead to problems – some of these things are good for the ecosystem but at a certain level, they are bad for the ecosystem too, potentially, so there’s all these steps, so what that project is doing is affecting the translation of precipitation to runoff, so it’s dampening that effect so subsequent arrows are all smaller.”
“So if we think about the actual mechanisms by which these changes are going to be carried through our systems, we can identify the opportunities for modifying them so we actually end up maintaining trees or flood protection services at the other end,” he said.
Example 2: Riparian setbacks and floodplains
Riparian setbacks and floodplains are clearly an important aspect of resilience for these kinds of systems, he said. With the projected change of more of the precipitation falling as rain rather than snow, a three degree climate scenario has a big change – a big reduction in the amount of snowpack and with a big effect on runoff.
“A 3 degree increase creates twice as much runoff essentially from the same amount of precipitation, so in this case, we’re actually amplifying the amount of precipitation by this other effect of climate change that’s affecting the snowpack, so runoff and peak flow are bigger,” he said. “This is why we’re thinking about floodplains downstream, because you’re talking about getting runoff that is potentially twice as much as what these systems were designed or even historically were used to, so a massive increase in flows, so a lot of the thinking right now is that we’re probably going to need wider floodplains to deal with that.”
He presented an example of a wider floodplain. “These are graphics from our Santa Clara River work, and you can see the amazing difference in the width of a river corridor historically here on a broad alluvial river and the big area of floodplain and riparian forest, and this is the area we have now on this example river,” he said. “You can imagine how the same peak flow affects a system like this versus this and how much more intensity and scour and loss of riparian and potential for overbank flooding there is.”
“So this is a way that we can actually impact the system back down at the peak flow level so while these vectors are changing and we may not have any control, we’re still maintaining these as not as altered, so that downstream, we hope we still are able to maintain the services and functions we want.”
In conclusion …
“In conclusion, there are many examples of how we can make our landscapes much more resilient,” Mr. Grossinger said. “In my mind, that’s the challenge of the next couple decades, I think that’s actually what we should be doing right now, we need to really mobilize and be effective at doing. We have a couple decades before those curves really ramp up, so we need to do that, and it really is every project, every time we plant a tree, every flood control project, every infrastructure project, those are all affecting the resilience of our system for the rest of the century.”
“It’s obviously a big challenge so we have to figure out how we can do that,” he continued. “Having a framework where we can organize our thinking and see the connections between the different parts of the system that usually are independently designed is critical, but I think the big challenge is how do we thinking for the environmental side is how to get this to have an effect on the big decisions made on infrastructure. I think that’s the sweet spot right here, trying to work collaboratively with different entities, the different sectors that design our landscapes and finding these sweet spots where we’re actually benefitting the full resilience of the system.”
“And with that … ”
For more information …
- For more on the San Francisco Estuary Institute’s Resilient Landscapes Program, click here.
- For the Landscape Resilience Framework, click here.
- For the Resilient Silicon Valley project, click here.
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