An interview with...

Jeff Mount, Ph.D.
Chair, Applied Geoscience, UC Davis

 

Give us a brief picture of what the Cosumnes looked like before all the development, before the problems it's facing today.

The Cosumnes River is like most Sierran Rivers supported a range of habitats prior to the arrival of the Europeans. The upland habitats that are typical of the forested areas of the Sierra Nevada that we all like so much. But the distinctive thing about the Cosumnes is the lower part of the Cosumnes enters the north delta so that it had extensive tracks of flood plain and wetland habitat and dense, dense riparian forest. I mean literally jungle style riparian forest in the lower part, prior to the arrival of the Europeans. So the Cosumnes annually flooded even during dry years there was flooding in the lower part of the Cosumnes and the water was stay on the land all the way into June, and produce these extraordinarily rich ecosystems which were driven by the annual flood cycle. So it was a wet place. A wet forested place with abundant wildlife. And the Native Americans took advantage of this. I mean a large number of them lived in that area of the Cosumnes because this wetness, this water, this seasonal pulse fueled very rich ecosystems and supported Native Americans in that area.

What is so important about the Cosumnes today?

The Cosumnes is one of the most important but ignored rivers in the Central Valley. It is the last un-dammed link between the Sierra Nevada and the Pacific Ocean. Every other major river of the Sierra Nevada is disrupted. Its connection is disrupted by dams. And because it's the last un-dammed link it has the natural hydrograph. It's got the natural flood processes. The seasonal flood pulses. There are two of them that we should worry about. One is the winter flood pulse. That's the one where everything gets moved around. Sediment and trees and carbon, nutrients…everything gets moved around. And that's good. That's healthy for a river. Then there's that spring pulse, that very subtle, gentle flood which is so biologically rich, so important in this system. The Cosumnes is the last one that really has this and that is what makes it an extremely important resource.

How did it escape damming?

The Cosumnes was sort of the ugly stepchild of the rivers in the Sierras and the reason is that the Cosumnes only heads at 75-hundred feet. Whereas the other large rivers like the American River, the Mekelome River, the others that flank them are all the way up above 11-thousand feet so they have abundant snow pack. Because they have so much snow they are ripe candidates for damming because basically what we do with dams is we trap the snowmelt. So the Cosumnes because its low elevation watershed doesn't have that much snow melt, that's how it escaped.

When the effort begin to try to restore the Cosumnes?

The Cosumnes restoration efforts have actually been going on for about two decades, with a whole lot of acceleration in the last decade. It's an association of partners, there's about nine partners, and it's a combination of government agencies as well as non-profits like the Nature Conservancy and even private landowners who are working together to basically preserve ecosystem function and sustainable agricultural practices in the lower Cosumnes. And basically what they've done is they are adapting to the cycles of this river, and adapting quite well to the cycles of this river. And they're still making a good living in farming down there. I mean there's very successful farming down there. There's very successful habitat restoration that's gone on down there. And basically what they're doing is living with the function of the river rather than fighting the functions of the river.

Could you talk about how conservationists are trying to strike a balance with their efforts on the Cosumnes?

One of the key things in the Central Valley here is we tend to view rivers or their attributes of rivers in two ways. Rivers flood. They get into our backyards. We don't want them to do that. We want to keep them out of our backyards. So that's one aspect and we manage them to try and reduce flooding. But at the same time we want rivers to have natural attributes like clean water and habitat and waterfowl for example and fish. And we view these two things -- that is, flood management as well as maintaining the ecosystems of our rivers -- as mutually exclusive, and that's just not true. In fact, you can do a lot for management of flooding and at the same time restoring habitat. And the Cosumnes is the place they're doing this. They are demonstrating to the rest of the Central Valley that you can live with flooding. You can actually be economically successful with areas that flood, and at the same time you can restore habitat and the values of rivers, the attributes of rivers. So that's the key. It's our learning laboratory, demonstrating to the rest of the Central Valley, "Yeah, you can live with floods. You can do well when there are floods."

Let me ask you about some of the specific threats to the Cosumnes, especially things like development.

The Cosumnes located just 20 minutes south of Sacramento as you can imagine is under threat. And the threats are several. One of course is the steady southward growth of Sacramento, the urban area of Sacramento, particularly Elk Grove. That growth, along with growth in towns like Lodi and Galt nearby is encroaching on aspects of the Cosumnes which make it unique and that is its' active flood plain. So the most obvious threat, the most visible threat to the Cosumnes is urbanization, the expanse of the urban area, the urban influence of Sacramento in particular. But the more subtle threats to the Cosumnes are things like the removal of ground water. In that area you have some of the most drawn down ground water in the Central Valley, in that region. There's the ground water beneath Elk Grove and nearby Galt that is at significantly greater depths than it was historically and what that has inadvertently done is contributed to the drying up of the Cosumnes River particularly during the fall. Rivers actually sustain their flow during periods of now rainfall by actually…the groundwater….the groundwater bleeds into the river. It feeds into the river. It's a thing called "base flow", and supports the flow of the river, but when you lower the ground water and it can't be connected with the river anymore, the river is actually charging the ground water rather than visa versa. So that's what's happening on the Cosumnes so you have extended dry periods during the Fall, which is a real problem because of course you have the Fall run Chinook salmon which try to make it up that river in the Fall and there's no river there when they get there so that's one of the significant threats. Another threat that we all have to worry about and is probably the most difficult to manage is invasive species, particularly plants that have moved into the Cosumnes. That is going to be one of the great challenges in the future. You could solve the groundwater problems and the runoff problems. You could plan for urbanization and do a good job of keeping it off the flood plain, but the wildcard in here is these non native species; plant species which are moving into that area and threatening the health of the native species.

And there are some native species especially of oaks that people are specifically trying to restore...

Actually one of the restoration targets down there is the riparian forest. These are these magnificent forests that existed up and down the Central Valley. Ninety-five percent of them are gone. And so they are trying to restore the forests and are using a variety of innovative techniques. I mean, there's the sort of traditional approach of planting acorns. And then of course what there are doing down there which is really unique and is quite exciting is that they are actually breaching the levies and allowing the river to restore the forests, because the river is depositing sediments and nutrients on the flood plain and cottonwoods and willows are springing up in these areas where you get new deposits on the flood plain and shortly thereafter oaks start showing up. So literally the river is doing the best job of restoration without anybody touching anything, just cutting a hole in the levee and letting the river deposit sediment, that's doing the job of restoration. That's one of the most important things we've learned out of the Cosumnes project. The river can do the job for you.

How was that lesson learned?

As is usually the case in restoration, we learn from accidents. We have unintended consequences that we learn from. On the Cosumnes river in particular there had been a breach in a levee in 1985 that deposited a large quantity of sediment and they plugged up the levee and forgot about the sediment. And then -- surprise! -- out popped a forest from this pile of sediment. In fact, it was a fantastic, dense cottonwood forest. Well, the Nature Conservancy said, "Well, let's do that again". And so in 1995 they put another hole in a levee and a tremendous amount of sediment was deposited and a forest started to grow out of it. Well what they didn't realize is that by restoring the natural physical processes it was more than just forests. Those areas that became flooded became havens for native fish. Native fish are extremely well adapted to the flood plain. In particular, threatened fish like the split tail, because they need to spawn on the flood plain. So by opening up the flood plain, these fish were coming out of the channel, feeding on all the great things to eat on the flood plain, laying their eggs, the split tail, spawning, and being very successful. So in fact, by restoring the natural physical processes, the ecosystems, the health of these ecosystems followed. And that's what we learned from that experiment down there.

What kind of resistance did they meet when they said, "We'd like to make deliberate breaks in levees"?

New ideas almost always meet resistance. There's almost always concern. And in fact as a society here in the valley we can find far more reasons not to do something than we can for reasons to do something and that's just the natural way it is. And so yes there was resistance, there will always be resistance to doing innovative restoration approaches like this, which might actually increase flooding on the flood plain. But the proof is there. It has actually caused no harm, in fact it has created benefit, net benefit in terms of flooding…lowering the elevation of the floods…and restoring the ecosystems. So, again, we have to take risks when do these things. We have to be willing to take risks. It's a principal of something called adaptive management. You've got to do these experiments and take risks. And that's what we learn from. There will always be resistance to this. It's guaranteed.

Are there any particular urgencies right now in terms of restoring the Cosumnes?

They have done a very good job of accommodating floods, but now the urgency is the rest of the year --that other three-quarters of the year where floods are not an issue. The rest of the hydrologic cycle, in particular the loss of groundwater and drying up of the river. That's an urgent thing to worry about. And that's one of the biggest threats. That and the other urgency of course is the progressive urbanization of the lower Cosumnes, because frankly, houses and floods don't mix real well. Houses and farms are a better thing, houses and floods, not a good idea. So that's the other urgency that they're dealing with in that area.

You said this was sort of a laboratory for the region for rivers. What are the lessons we can apply to other rivers in the area?

The Cosumnes is widely recognized as a learning laboratory and the lessons that we can learn there are straightforward. One, there is direct measurable benefit when you restore a natural physical process which is tied to the hydrologic cycle. Meaning, restoration of seasonal flooding produces immediate, tangible, recognizable benefit. And they've even come up with a method to do it, which does not increase flood damages. So that's one of the primary lessons right there. The second is, and it's a key lesson, you can still have viability and ecosystem restoration. They can work hand in hand. They can actually enhance each other. They don't have to be mutually exclusive. So that's the other great lesson that's going to come out for the rest of the Central Valley. And the third thing is, we're actually quite surprised how this restoration of natural processes seems to favor the native species and actually discourages the non-native species. So there's another lesson for management of alien species in the valley.

What will the picture look like when these efforts are completed?

This question comes up a lot. What are your objectives? What are your restoration objectives? And everyone has sort of a muddy view of this. I want it to be healthy ecosystems, and very few people actually draw it out like a diagram or a sketch like a building might look, it's not like you can design that in restoration. You can only hope to restore function and attributes. What I mean by that is that a system which has all the variations of the seasons and has the right level of productivity to support diverse life, and that's the key thing, diverse life. The second aspect of it is that you want variability in the system. We all think we want everything to be like a nice garden. That's not the way the earth works. The earth works with long periods of boredom and short periods of terror. And what they've done by restoring flooding is they've re-introduced terror into the environment. Well it turns out that's what those ecosystems are adapted too. You need disturbance. So for me, what I would like to see in the future, and I'm just speaking for myself, what I would like to see in the future, is a system that restores the natural processes of the annual hydrologic cycle and occasional disturbance because I'm confident that what that will produce is a mosaic of habitats which support very diverse life in that region. So high biodiversity and also allows economic activities like farming to continue down there. That is sort of the ideal end condition. It's not going to hold still. It's not going to be a nice garden. It's going to be occasionally flooded and there will be some chaos in it, and that's a healthy thing for the environment there.

Presentation also made possible by a grant from
the Great Valley Center