HEC-RAS vs. HEC-6

Dear Manager,

I am a student of the graduate school(National Chung Hsing University of
taiwan). For the reason preparing for my dissertation--------The trap
efficency of settling basin (The chambling percentage of grit chambler),
I am searching for the software or modeling which can solve the
trap efficency of settling basin. Because it is important for the
problem ------- "upland soil is washed away in taiwan"So,I have some
problems about the different between HEC-RAS and HEC-6 :

1.Is HEC-RAS a most new version of HEC-6 ?
2.Or is there any other software that I can put in use ?
(I had download the PDF Files of HEC-RAS 2.2 and HEC-6 User Manual )

Sorry for spend your time to read this E-mail,and can you answer me a
E-mail ?
Thank a lot !!
Your assistance is much essential.

Yours sincerely
friend Chi Li Lin

Dear Chi Li Lin :

Note that HEC-RAS does not include the sediment transport modeling that
HEC-6 has. However, I would recommend looking at SWMM or HSPF. It can be
used to model a detention pond, and you can determine the time of
retention within the pond for settling of the sediment. Neither HEC-RAS
or HEC-6 can do that.

Sincerely,

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