Problems with Initial Attempts
Flow through buildings and tanks
No flow accumulation in creeks
Had to account for:
- Tank dike areas
- Building foundations
- Surface ponds
- Creeks
Notes:
The thing that is unique about developing the facility terrain is that when you are using the watershed delineator tools, you typically don’t focus in on an area that is so small. My first attempt had obvious flaws as flow was running through buildings and tanks, and there wasn’t much flow accumulation in the creeks. I determined that there were a few different problems. The dike areas around each tank were being filled to a flat terrain during the fill process. In the real system, there are pipes between each dike area which drain water from one area to the other until there is a final outlet. I also realized that the building foundations were not high enough in the dem to distinguish them from the rest of the surface cover. Yet another problem was that a few of the lagoons or surface ponds were also being filled. To solve these problems, I first used ArcTools to add no data cells in the ponds, and I used ArcTools to dig trenches between each dike area. I did not know the locations of these pipes, so I set them for now based elevations and had the final outlets to Marcus Hook Creek. In ArcTools, the trench was set to a value of 1 ft., but during the fill process, this trench will be filled until it reaches the lower end of the land surface. I then took this revised dem and burned in the tanks and buildings. The procedure is very similar to burning in streams, except this time, the original dem elevation is held constant and everywhere there is a tank or building, the elevation is raised by 50 ft.