 Thank you. So good morning everyone, we changed totally the topic. So I'm fluvial geomorphologist, and I use models, and very shortly develop one so I will start just by defining what industry in large wood is, and why it is important. So why do we care about this, and then I will focus on the first numerical model that was developed to simulate the transport of wood in rivers called Iverwood. I will show you how we validated this model using data from flume experiments and field observations. I will show you also two main applications. So how we use the model to explore wood dynamics in rivers and better understand rivers in general. And also I will focus on the related hazards or potential hazards related to wood transport. So industry in large wood refers to down trees, trunks, root buds and branches that fall in a river. So they are the base of the rivers organic matter supply and in some rivers together with the living trees. They are a major reservoir of organic carbon. So industry falls in a river. It triggers a lot of processes so it creates an abstraction that is a source of flow resistance and energy dissipation which is affecting the hydraulics so it's usually lower in the flow velocity, increasing the water depth and affecting the flow resistance and so this has an effect on the sediment dynamics and is influencing the sediment storage and sorting, and it's also affecting morphodynamics so it may enhance channel mobility shifting and it may influence channel widening river bank erosion. So wood adds physical complexity to rivers and so improves habitat diversity. And this is not happening just at the very local scale. It's actually influencing river processes, forms and functions across scales. It may affect channel and flat plain connectivity and eventually in the long term is influencing fluxes at the catchment scale. And so wood is also affecting the water chemistry and temperature. It provides a hard substrate for the biofilm to colonize. It provides food shelter and nursery areas for aquatic species. It's also influencing the establishment of vegetation and the vegetation sections and the development of islands in rivers. And it's also the combination of the or the interactions between the flow, the sediment and the water provides better conditions for many species and not only aquatic species so wood is influencing the entire food web. And so this is why wood is a key element sustaining river, rivers health, and also providing resilience to river ecosystems. And this is the reason why after centuries, removing wood from rivers, we are actually seeing an increase in the rain production of wood to rivers worldwide. So wood is increasingly used for river restoration. Although most of the time wood is stable in river channels as sediment, during flats, large quantities of wood might be transported. And so this is an example from a river in Utah. And so where this wood goes, it might encounter obstacles like critical sections like bridges or dams, and so make us some hazards. But what is really important to highlight here is that none of the hazards posed by wood are inherent to the wood itself so the wood is not the problem. The problem are the infrastructures that we designed to not allow the wood to pass. And so we are artificially enhancing the trapping efficiency of rivers and the transport capacity. And I will go back to this later. So there is a vital need to understand wood dynamics and integrate this understanding in the way we manage rivers. And so this is why we recently defined the wood regime in a similar way than was done for the flow and the sediment regimes. But compared to the flow and sediment regimes that have been studied for decades, even centuries. The science or the research in wooden rivers is relatively young. And we face a very important limiting factor is the lack of data. So there are no gauging stations monitoring would transport. This is also why we still face major scientific questions that might sound quite basic but we still don't fully understand how wood moves in rivers. How much good we can expect to have during a flood when might be transported where it goes and where it's deposited and what are the potential impacts and hazards. So numerical modeling is a powerful tool to explore these questions. And so before talking about either wood, let me introduce you either. So either is a 2D hydraulic model that was developed. So to simulate the free surface flowing rivers and estuaries. It was developed mostly by them by scientists at the University of Catalonia and La Coruña in Spain. It is distributed for free. You can download it on this website. It is both in English and Spanish. And the first version was released in 2010. So here I listed some of the main characteristics of the model. So hydrodynamics are solving the sandstone and equations in two dimensions using an explicit finite volume scheme on unstructured measures. It solves of critical and supercritical flow. It's conservative. It includes several models for turbulence. It solves morpho dynamics and sediment transport. And it is integrated in a user friendly pre and post processing interface. So as with any other hydraulic model either has been applied for studying hydromorpho dynamics and assessing flat hazard and risks. But also for eco hydraulics and fish habitat and water quality and it has many modules that allow the model to solve or to study other processes like dam reaching hydrological processes, pollutant distribution, or it also allows the simulation of non Newtonian flows like no avalanches or debris flows. So a few years ago, already 10 years ago, we coupled a module to simulate the transport of wood and we did this by coupling a Lagrangian scheme so a discrete element approach to the Eulerian model. So I will not go into all the details but so we simulate individual pieces of wood and the incipient motion of these pieces of wood, assuming them as cylinders with or without groups is based on a force balance and so we have the driving forces, the drag forces and the gravitational forces and then the friction the resisting forces and these are the main parameters that are considered in this equation in this force balance. So we have the density, the size of the wood, the water depth, the flow velocity and some coefficients the friction and the drug coefficients. So with them, we have two different types of transport mechanisms so wood may slide or drag on the riverbed or may float float. And so the model also includes interactions between the wood and the geometry so the morphology of the river interactions between the wood themselves by assuming elastic or an elastic collisions. And interaction between the wood and internal conditions like bridges. I said that the module is fully coupled. So this means that the presence of good has an influence on the hydrodynamics and the hydrodynamics are controlling the motion of the wood pieces and we did this by adding a drag to the sample and the question. So, since we started developing this model, as I said more than 10 years ago, we used observations to validate the model so the first validation we did was in a very simple setup in a very straight, small channel with some obstacles and constraints to get some recirculation songs, and we focused on the trajectories of floating cylinders. And then we compare their trajectories rotation velocities. And so here I show you one example of this comparison and as you see the model was capturing the behavior of surf in the flow. Recently, we added more complexity to the model. So we validated the behavior of not only the floating logs but also these dragging logs. And so we use a braided flume with a complex morphology, which is characterized also by shallow waters. So in these systems, the wood is not only floating is also dragging top of the bars and on the channels. And so here we focus on validating travel distances, the accumulation of wooden jams and the effect of roots. So this is an example of one of these runs that we need to reproduce the flume experiments. And here I show you in this box plots, we compare the flume observations with the numerical model, focus on the travel distance for different scenarios using different sizes of wood. And so you see that we, or the model, again reproduced the patterns of surf in the flume, of course with some differences and the main difference here was that the variability of surf in the numerical model was much smaller than in the flume. Still, we have some ways to add kind of stochasticity to their numerical model, but I will not go into details. So I said that we lack of surveillance so we are trying also to fill this gap, and we are doing field surveys. So we are using metal and plastic tax to track boot in rivers but we are also using radio frequency transmitters. We use drones and cameras, and we also use citizen science so we use videos of people just recording plots with a lot of wood. And so we extract quantitative information from these videos, and we are currently developing machine learning algorithms. So we are using deep learning to automatically detect wood, detect and track wood on the drone imagery and videos from video cameras. So we use this information to get the positional patterns and wood fluxes that we can use to validate the model. So two main applications now, one application to better understand wood dynamics. So we use the model in a multi-scenario, multi-run approach, and so we compare wood transport in contrasting river morphologies. So we compare two river reaches, one single thread channelized and another one multi-thread rated river reach. And so the first thing we can observe in this graph is based on the transport ratio. So meaning one means wood transport, so all pieces entering the ring, the reach are going out. So we observe a significantly higher transport capacity or transport ratio in this channelized river reaches versus the rated morphologies. But we also observe that the capacity to transport larger pieces was larger in this straight channel. So here we again have the results from different scenarios. And so we observe that in these straight channels, the flow is able to move very large pieces of wood while in these rated systems, all the small pieces are mobilized. And so by analyzing rivers, what we are doing is artificially increasing the transport capacity and competence of the flow to move the wood and potentially enhancing hazards downstream. We also analyze the position of wood. So by again running multiple scenarios, we compute it at the positional probability. And so we observe that this probability to, so this is the positional probability changes with these charts. And during high flows, the natural place for the wood to be deposited is the flat length. And so again, by modifying the connectivity between the channel and the flat plane, we are decreasing the position of wood and then increasing the transport downstream. In this other example, we analyzed, we simulated the confluence of two rivers, one of them supplied with wood, and we explore interactions between the flow, the wood and sediment. And so in this graph, you have water elevation and critical diameter, meaning the size of the sediment that the flow is able to move. And so if we compare to scenarios with and without wood, and so if we focus on the water elevation, so the gray lines, we observe that the presence of wood increased the water depth downstream from the confluence and lower the velocity. And now if we look at the critical diameter, we observed also decreased in the sediment size that the flow is carrying. So wood influences the flow transport capacity. Regarding the potential assets, one of the first works we did was to use the model to identify critical sections. So in this river crossing a town where several bridges are located, the model allowed us to identify the one that was more prone to trap wood. And we, for the first time, used this to include wood transport in a risk, in a flat risk assessment. And so we quantify the potential losses, and we compare the scenarios with and without wood, and we observe that the blockage of bridges cause up to 50% more economical losses for the same discharge. So the bridge clogging or the blockage probability depends on many factors. So the model allowed us to explore these different factors, and one important factor is the discharge. So again, running multiple scenarios for this river in Poland, we computed this blockage probability and we observed that in general, the blockage probability increases with discharge, but until a certain threshold. This means that for very extreme floods, the blockage or the presence of wood might not be so relevant. The flood is huge anyway. But for intermediate floods, the transport of wood may significantly increase the flooding. Not only the discharge also, of course, the amount of wood and the size of the wood is important. And again, here we found address hole, which is related to the size of the wood relative to the size of the channel or the bridge. There are other processes that might be happening when a bridge is blocked, not only this backwater effect or this flooding, but processes like erosion, so a scour or widening. So we explored this in this river in Chile that is heavily affected by volcanic eruptions. So there is a huge supply of sediment and wood. And so we again use the model to explore this flow of wood sediment interactions and we observed that by blocking the bridge with wood, we enhanced the scour, so the erosion we see in this graph here. And the model also allowed to see that among the different piers, the bridge piers present within the channel, one of them was actually more prone to trap the wood and this was observed during a past flood in 2015. So just to finish, I would like to stress that, of course, the model is just a simplification and we are trying to use a deterministic model to reproduce a quasi stochastic process. And so still there are many limitations and at the same time, but we can use the model to test hypotheses, run multiple scenarios, and we can use it to understand processes that are very difficult to observe in rivers. And with this I finish and I thank you for your attention. This is an excellent overview for flu field of flu field your morphologist and I think it's linked well to Kyle's talk of yesterday. We'll allow for one question before we move on to the next talk. If there is one. Thank you for the great presentation. So I have the two questions. The first one is related to the model so your model use different types of measures I mean like a mesh for the fluid other one for the sediment for the good. And the other one is what type or technique you use for analyze the fluid in the experiments. So the model uses two different measures one for the hydraulics and the morphodynamics and one for the wood. You'll see Salagrandian mesh. So yeah, we have to couple the two measures. And the other question is the techniques about the technique for analyze the flow in the flow in the experiments. P I B or something. Yeah, we use measurements of like flow velocity measurements, ABCP. And, for example, in the first experiments I show this we did ourselves in the lab, the other ones in the brightest flume. And before and then we use the data afterwards so I cannot tell you all the details but some of the experiments were recorded and we used also the video frames and the recording. Thank you so much.