Grid Generation

Hello EFDC users and EFDC team!

I am confused.

What are: and how do they differ:?
1. stretched or sigma vertical coordinates
2. Cartesian or curvilinear, orthogonal horizontal coordinates

Since in the software
EFDC has two grid generation type:
1. Cartesian
2. Curvilinear

Isn’t that cartesian is different from curvilinear grid generation? What is stretched or sigma vertical coordinates? How do you use that in EFDC to generate a grid?

Thanks in advance.


Hello Armi,

EFDC uses sigma or stretched vertical coordinates. It means it has the same number of layers everywhere in the domain. There may be some cells which have different depth, but no matter what depth each cell have same layers i.e. the layers are stretched from the bottom to the top of the water level. Z vertical coordinate has also been used in EFDC but DSI hasn’t released the version with Z vertical coordinate yet.

Grid generation

EFDC has options to use cartesian, and curvilinear grids. However, you can have some portion of grid cartesian and some portion curvilinear. Creating a cartesian grid through EE is very simple especially if you want to create telescopic or simple constant cell size grids.
Recently DSI has released a very robust curvilinear grid generation tool “CVLGrid”. The name CVLGrid referes to the curvilinear grid generation. If you will be using EFDC model for quite a while and want to make nice grid then this tool might be for you. You can also request for a trial license and eventually purchase it.

If you have grids from the previous existing EFDC model or from SeaGrid, Delft, Ecomsed etc. there is a function in EFDC which allows you to easily import such grids easily.

Good luck.

Janesh Devkota