Floodplain Mapping Suggestions

I'm writing in order to ask you a question about the floodplain mapping module of RMS.

I'm sure you're well acquainted with this problem since it is the prime drawback to the use of "DTMs". The problem I am having is the following. When I draw the advanced topo map water surface, I end up with a "floodplain" that looks a lot like minnesota, that is a bunch of disjointed ponds. I know that this kind of thing ca result when a DTM package uses third or fourth order polynomials to generate a surface. I've tried interpolating sections in the areas that I find gaps and sometimes it works and sometimes it doesn't. Often this just moves the gap.

Do you have any good ideas from prior experience about how to make RMS draw a reasonable looking floodplain? Also, is there any way to control the manner in which the tin is created in order to avoid these false pockets?

Thanks for your help,
Matt Shupe
c/o Simons & Assoc.
mashupe@simons.com

We do not use 2nd order derivatives in our tinning engine (although it can do that), as you refer to below. We have had this problem as well when trying to infer trends with poor data using 2nd order derivatives.

This problem you are referring to is generally caused by simple lack of data (i.e., just too sparse). What you can do is place a man-made point (at the appropriate elevation) at locations where the floodplain mapping is failing. Note also, that your original TIN might have pits in it (caused by your tin engine). You might be able to do some smoothing of the original TIN by perhaps gridding the data. DTM Module can do this. Or, use a triangulated grid so that you can maintain break lines and points if the grid is not accurate enough.

Please contact me should you have any additional questions.

Sincerely,

Chris E. Maeder, M.S.
Senior Technical Engineer
chrism@bossintl.com