In the previous post I showed that the main reason for flooding in St Helena is its location in the low-lying terrain between the Caroni and Guayamare Rivers. This post will explore one option of flood mitigation in the area – levees. Levees have been used for centuries to protect areas against flooding. Portions ofContinue reading “St Helena Trinidad, Flood Mitigation Option #1: Levees!”
Tag Archives: hec-ras
St Helena Trinidad, Flooding Causes
In a previous post I showed a hypothetical floodplain map of St Helena, Trinidad. This is a lot of flooding! St Helena is one of those areas that are notorious for flooding whenever rain starts to fall in the area. But why? The answer is mainly its location. St Helena lies between two rivers: CaroniContinue reading “St Helena Trinidad, Flooding Causes”
Caroni River Basin 2D HEC-RAS Model Overview
I had a request to see the model that I used to create the floodplain map for St Helena in my last post. I used RAS 6.6 to develop the model along with all the inputs I described in my previous posts: Terrain, Land Cover, and Soils. Here is a brief overview of the model.Continue reading “Caroni River Basin 2D HEC-RAS Model Overview”
St Helena – Trinidad Floodplain Map
Let’s talk about floodplain maps. Floodplain maps have many uses, including guiding development and zoning, identifying the most vulnerable areas for emergency preparedness and response, analyzing property risk, and water resources management. Here is a hypothetical floodplain map of St Helena, Trinidad. If you have been following along with all of my mapping posts soContinue reading “St Helena – Trinidad Floodplain Map”
2D Mesh Breaklines
In the Viewing the Results post, we saw the neat Particle Tracing feature in RAS Mapper, which us to easily visualize the movement of water. However, if we look closely enough, things look a bit strange. The particles seem to be going straight through that road embankment (The Priority bus Route) as if it doesn’tContinue reading “2D Mesh Breaklines”
Boundary Conditions – Normal Depth
From the previous post, we saw that water was not leaving the model, causing a build up of water at the downstream end (although the downstream end is the Caroni Swamp where we expect water to be). To fix this, we add a Boundary Condition Line at the downstream end of the model. in RASContinue reading “Boundary Conditions – Normal Depth”
View Results
Now for the fun part! Now that we have successfully run the RAS model we can take a look at the results. This is easily done in RAS Mapper, which has several different options for viewing the spatial results. Under the Results section, the ShortID of the event if shown along with Depth, Velocity, andContinue reading “View Results”
Create the Plan and Run the Model
The Plan file contains the settings used to run the model such as the simulation window, what time steps to use, and what equation sets to use. The main things that we will do for now is ensure that the geometry and Unsteady Flow files are associated, and enter the Simulation Time Window. Here IContinue reading “Create the Plan and Run the Model”
Apply Precipitation
Now we will set the rainfall that will be applied to the mesh during the simulation. I will most likely have a few posts on how to actually go about developing this rainfall table, but the goal for now is just to get a working model and then make it better. So in interest ofContinue reading “Apply Precipitation”
Create a Mesh
The mesh is what makes it a 2D model. Read the RAS documentation to learn more about the properties of the 2D mesh including computation points and cell faces. In a 1D model, rivers are modelled using cross-sections across the floodplain, distributed along the river. In a 2D mesh, I think to think of theContinue reading “Create a Mesh”
Mapping T&T 