 Okay I want to talk a little bit about the relationship between turbulence and boundary layer thickness. So I've recreated our drawing here where we have a flow depth with the average flow speed for this particular case. So we talked a little bit about how friction keeps the flow at zero right at the surface and the friction within the fluid influences the flow speed as it goes up. I want to talk about that in a little bit of a different way. And in water flows this main flow is turbulent so we're going to talk about it in terms of the water flow. And as we know turbulent the parcels of water move really irregularly and sometimes they move down into this boundary layer. And that's one of the ways that the flow speed is increased at the top of the boundary layer. There's both the friction within the flow but then also this increase of turbulence. And so anything that increases the turbulence of the flow tends to lead to more turbulence being directed down towards the bottom of the bed. So if we look at our Reynolds number one of the ways that we can increase the Reynolds number which is a measure of the turbulence is to increase the flow speed. So if we have the purple line here represents a different a faster average flow speed. Here we still have the flow being zero right at the surface but there's a bigger change in flow and the boundary layer is often thinner. So here for the purple flow we have a thin boundary layer. And that's because there's a lot of turbulence coming from the high turbulence in the flow and transferring some of that kinetic energy that high flow speed down into the zone here. Similarly if you increase the flow speed your boundary layer often gets thicker because there's less turbulence to mix in with the flow. That's probably not a linear scale but we're okay. So you end up with a thicker boundary layer in flows that are on average much slower. And that change in the boundary layer affects what grains and things feel in the flow and it affects the sediment transport. I almost forgot to say thanks for watching.