I am designing a 84" sewer pipe that will cross (perpendicularly)under a creek.  What methods can I use to compute the scour depth of the creek so I ensure that the pipe is placed below this depth?
I have obtained information (Q) from the closest USGS gage from the USGS website.  In my research, I found a document titled "Computing Degradation and Local Scour" (Technical Guideline for Bureau of Reclamation).  Is this something applicable to my project?  Is the type of scour I need to analyze considered "local scour"?  Also, I found an NRCS "Scour Calculations" document that I'm about to start reading through.  Does anyone have any advice?           

civilengineergurl

Take a look at the FHWA website:
http://www.fhwa.dot.gov/engineering/hydraulics/index.cfm
You may also take a look at the ACOE website:
http://140.194.76.129/publications/eng-manuals/

There is plenty of information on scour.

 

besides local scour, you should also evaluate long term degradation or agredation and other forms as shown below:

Total scour, for a given application, should consider the following components of scour:
a. Long-term degradation of the bed of the watercourse.
b. General scour through a specific reach of the watercourse.
c. Local scour.
d. Scour induced due to a bend in the watercourse.
e. Scour associated with bedform movement through the watercourse.
f. Scour due to low-flow incisement.
Total scour (Zt) is the sum of each of these individual components (Zi) of scour. Total scour can
be expressed as:
Zt = FS (Zlong-term + Zgeneral + Zlocal + Zbend + Zbedform + Zlow-flow)

You will need to get permits including 404 and also one from the State or County to cross the river. They will review your calcs and may have requirements on the procedures to use.