You can use the export function to export the elevation map after erosion to a .asc file for further studies in ArcGIS.
The map being used is the Crater Lake National Park in Oregon. See below for an elevation map.
Rain drops are created randomly on the map based on the rain rate parameter. Rain drops will run to the neighboring patch with the lowest elevation. Besides, if there are already water in a patch, the height of water will also be added to its elevation, when raindrops are selecting the patch to run to. If a raindrop can not find a neighboring patch with lower elevation, it will stay where it is and become water. When raindrops run to the edge of the map, they are removed from this model.
See below for a video recording a simulation process:
This is an image showing the result after 700 ticks.
This is a map showing the amount of water in scaled color, where darker color implies higher volume of water.
See below a video for the verification of the model:
Please visit the following link for the code.