Remote Sensing Deltas
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Hill differential equation
Transcript: English(auto-generated)
00:07
Okay, I think it's time to start our last presentation from this first slot. And it's my pleasure to invite Mr. Levi Josan to tell us more about remote sensing of deltas.
00:25
Hello, morning. Can you hear me? Everybody come in, there are a few spots left. Don't need to stand. And now for something completely different.
00:41
Any fan of Monty Python today? Okay, so my name is Levi Josan. I'm originally from Romania, working in the United States for now 28 years. And welcome to Romania. I'm going to talk about something different, deltas.
01:03
Nothing to do with open source except in the last slide. So let's see how you fare through this. Some technical problems. I was too careful to follow the guidelines of the organizers. But it's fine now. Page up, page down. Okay, let's see.
01:23
Does it work? Okay. So I'm a marine geologist. And one of my focuses is the coast. We know that many people like the coast. They want their own little villa to live there.
01:42
But we are ruining the earth. And the coasts are the front line of this war with nature. Among the most endangered coasts are deltas, which are very flat landscapes and very expansive.
02:02
And because of that flatness, they are easily overrun by sea level rise and other problems that we put pressure on the coast. So in the upper picture is a photograph from the Danube Delta, how a delta should look in natural conditions.
02:28
And below it's a shot from Vietnam in the Mekong Delta. And at some point was similar. But now many deltas are occupied for different activities.
02:44
Cities, agriculture, different fisheries. And why are deltas so important? Because they are cradles of life. They are very productive. People were attracted to these regions for a long time.
03:01
Some people say that civilization started in deltas, like in Mesopotamia. So we are in love with deltas, but we are destroying them in the same time. And if they will be left to their own device, even if sea level rises, they would adapt.
03:20
But we don't like that. We want to stay everything the same forever. And that's not the way to work on the coast. So what's good about deltas? We just discussed. They are expensive, they are productive, they are biodiverse, and they can be lost.
03:44
And this is how it looks, a shot from the Mississippi Delta from a plane I took three years ago. There were marshes all around, but now they are only left the natural levees. This is a very depressing trip that I had there.
04:03
And that's a picture of how the Mississippi Delta looked in the past. And everything in red is already lost from 1937. Deltas are very complex. It's on the left side of this.
04:20
But we want to keep them simple and see how we can help. So what do we do? Deltas are also really beautiful. You can see them from space. They are beauty. And any delta doesn't look like any other one.
04:41
You can see here a few examples. Our Danube. And if you are here in Romania for the first time, you should come back and see that jewel. That's the Danube Delta. But they are different in terms of landscapes because they are under different factors that influence their evolution.
05:01
And how can you put this variability in processes and in shape together? What is the essence of a delta? How can we help them stay above sea level? And that's from a paper that we put together in 2014. And the rationale here is a delta is a new land built by mud that's brought down by rivers.
05:31
If you don't have mud, you don't have a delta. So we looked at, on this side, the maximum sediment that the river brings and the minimum sediment to keep it at sea level.
05:47
And that's the way to bring them together. That's the essence of a delta. So we can see here they are logarithmic scales. And one-to-one ratio is where the red splits from the black.
06:05
Everything that is in the red zone are deltas that have a deficit of sediment. Everything that's in the black zone, they are healthy. The size of the symbol in the graph expresses the size of the delta.
06:22
So the big circle, it's over 10,000 kilometers squared. These are huge mega deltas, mostly in Asia. Danube delta here, it's a medium-sized delta. And there are small deltas, like in Western Europe, the Ebro.
06:41
So if we want to save deltas altogether, we have to move them from the red zone to the black zone. Now, if we dam rivers, and we did this for 100 years.
07:04
We put dams along the river, along the tributaries. We stopped the sediment behind dams. So the red zone migrates, more deltas become endangered. And that's the true picture of the deltas today, the red zone migrates. That's where we are now.
07:21
Only small deltas are viable. So to keep them alive, we need more sediment from somewhere. Either bypass dams or bring new sediment there. So the question is, what's to be done? That's a time-honored question in every aspect of life.
07:44
This is my friend, Lenin. Heavily dammed rivers carry less sediment. More efficient use of available sediment can mitigate land loss. He didn't say that, I said that. So let's look at the picture of deltas around the world.
08:03
Starting with Ganges-Brahmaputra, that is a huge one, and going down. And what do we show here? Deltas first, they build into the sea. So that's called progradation. They also keep above sea level. That's called accretion. And we can see here in million tons per year, the sediment that goes for
08:24
progradation is dominant. To keep it above sea level, it's a very small slice in blue. So that gives us an idea, a solution toward a solution.
08:40
So if that sediment that goes and is lost in the ocean, is somehow kept on the deltaic plain, we have a chance to keep some deltas alive. Now, this is the situation in natural conditions before putting dams on. Now, the red arrows show, again, in logarithmic scale, these are huge changes.
09:10
What was the decrease in sediment after dams were put in place? And you can see big changes, mostly negative. So we have to forget about that sediment, but still, the gray zone, it's huge,
09:24
and that's lost to the sea. How can we keep that sediment on the deltaic plain? So there are several solutions that are being tried, or will be tried. And one is to make more breaches from the channels toward lakes or marshes.
09:45
It's called crevasse plays, or build internal deltas in lakes that would trap sediment. And that's being tried now in the Mississippi. The other way is to move the course of the river all together.
10:02
Move it in another favorable position and build a new delta. And that's being tried, this is the Brazos Delta near Freeport in Texas in the 1930s, and they built a new delta.
10:20
Or take an example from young deltas that trap a lot of sediment, and that's the Kiliya subdelta in the Danube. And what is striking here, and that's in the juvenile stage of a delta, you have a lot of channels that spread sediment on the delta.
10:40
In the more mature stage, the number of channels decrease, and more sediment is moved toward the ocean. Where do I have the time? Okay, hurry up.
11:00
The other way to put sediment on the delta is to put organic sediment, marshes. The plants that die and rot, they leave behind organic sediment. And that also keeps a delta plane above sea level. So now if we put marsh sediment, that's the situation without them.
11:22
We add that, excuse me. This is with sediment, 90% organics. You can see a lot of deltas move in the good zone, but you cannot have 90% organic. As a geologist, I know that organic sediments in the delta that's preserved is about 10%.
11:42
And they don't do well if they don't receive water and mud during the floods. So what's realistic? Maybe 50%? Still, a lot of deltas are saved. And for that, we need to bring more water and mud toward the delta.
12:01
And that's the new delta here. You see the network of red channels that were not built to keep the delta alive. They were built for fishermen since the 1930s. But as an experiment, an inadvertent experiment, they also keep the delta in good condition.
12:21
Danube is more stable than other deltas around the world. And we can do that in many other deltas. Another solution is to leave a delta to its own device. And this is a modeling study that we did. If you leave the delta under the influence of waves, it's eroded and builds the coast on the sides.
12:44
And you have healthy coasts on the sides. They are seen as giant sand engines. So we're heading now toward designing deltas. We need to design deltas to keep them alive. And now we come to open source and via remote sensing.
13:03
These are huge animals, deltas. You cannot study them in the field without a lot of money, a lot of people. So the solution is not in the field. The solution is above. And I just want to present a start for this.
13:24
It's called Delta X. It's a project that starts this year. And I'm part of it, but it's led by my friends at JPL in Pasadena. It's a NASA funded project that starts in the Mississippi.
13:42
And, briefly, we want to fly sensors with the NASA planes over the delta. At the same time, have teams on the ground and measure different properties that interest us. And input this calibrated data into a model, a fully stochastic model.
14:08
And try to predict where the water and sediment will go. And, in the end, design where that sediment and water goes. What do we want to keep alive? And that's the physics of it.
14:20
Sediment goes toward the marsh when we have floods through overflow. We want to understand the physics. We need the parameters to input in the model. And we get those from above. So water surface slope in the channels that gives us discharge. Water levels change in the marshes where it could be in the field.
14:42
It's hard to measure. It's very small and hard to access. Sediments in the water, how much sediment load exists. And vegetation structures to tell us what's going to be there. How much is going to be left over after they die. And the field data for calibration. We measure discharge sediment.
15:03
Accretion rate of mud. Vegetation structure. Organic accretion. And everything goes into a model that hindcasts and forecasts what's happening in the delta. So we'll have a few campaigns with a repeat pass radar interferometry for water level change.
15:27
For water flow in situ. Measure for calibration. Spectroscopy for vegetation. And radar interferometry for water height and slope. We'll cut vegetation and measure it.
15:41
That's going to be done with the NASA planes. And different stages of the tidal cycle. And we'll have teams on the ground that will do measurements in the same time. And another important component is the monitoring of the different properties in the delta with stations that are where we can get data in real time.
16:06
And these are the cream stations that now have a history in the Mississippi for 20 years. And they are improved better and better. Is it doable? Yes. We tested that.
16:22
And this is for example water surface elevation for 20 kilometers at a resolution of 2 centimeters. I'm sorry. Water surface in the marshes. And accretion rate based on the sediment.
16:42
And now open source. Why do we need open source? Because that's the distribution of deltas in the world. Almost a billion people on this earth depend on deltas in a way or another. And more than us, life in the sea and in the rivers depends on deltas.
17:00
So this cannot be done with closed solutions. It only can be done through a system of monitoring, modeling and sharing that only the open source can offer. Thank you very much.
17:21
Thank you for the very interesting presentation. Do we have any questions? Come on. Only in the United States? During the project you'll study only the USA deltas? It starts there.
17:41
Our goal is to extend it through satellites, micro satellites to cover in the end the entire or the entire region, regions with deltas. Please.
18:04
Are you familiar with the building with nature initiative? Yes. It's a wonderful initiative. And also Open Earth from deltas. Yes. We are partners with them. We actually work with the DELT3D to improve for the modeling.
18:25
Thank you very much for coming. Any other questions? We still have some time left. I think I have a question. Sure. You mentioned several parameters that you are interested in, but you didn't mention anything about carbon sequestration,
18:42
which might play an important role when discussing about deltas. It's not a direct objective, but you can imagine that the data that we collect will be useful to that. It's not something that we stated in the project. Once you measure organic accretion, once you measure the type of sediment that comes in the river,
19:07
carbon storage and carbon release in deltas is still a gray area. Thank you.
19:24
Hydrological modulation of water? Yes, so the idea is to get discharges from slope in different channels, channels as small as five meters through the radar and calibrate that with direct measurements
19:45
and input it into a hydrological model and morphological model and vegetation model. So we'll have output hydrology in the channels and the marshes and we'll have many other things beyond that.
20:07
Thank you.