I'm trying to develop an IDF curve for Craig, Colorado. I'm using the UDFCD Rational Method spreadsheet and have the appropriate 1-hour rainfall depths but I can't seem find the appropriate coefficients for the Rainfall Intensity Equation (a, b, and c). Is there an adjustment factor or a table...
Is there a way to analyze a simple storm system for a user defined peak flow in Autodesk's Storm and Sanitary Analysis? If not what program (preferably free) would you use? I used to use Bently's stormcad for these quick calcs but we decided to drop the license.
Thanks
What percent impervious/runoff coefficient would you use for the Rational Method for an area that has just been re-graded and probably has hydromulching or something similar but no actual vegetation yet? Also has steep slopes. I'm using 5% for undisturbed areas and was thinking 30% was...
Any flume experts out there? I'm using WinFlume for the first time to design a ramp flume for an irrigation ditch intake. I'd be very grateful for some peer review of my design (see attached WinFlume file and output pdf's).
The existing ditch is between 3'-4' wide at the bottom...
A little bit of background...
I'm doing a peer review of a Stormwater Masterplan by another consultant. The watershed has ten sub-basins, six of which are included in FEMA's FIS for the region, meaning there are published peak flows for the 100-year flow (I'm focusing on the 100-year peak flow...
Proposing a 60" culvert at an access road crossing of an intermittent creek on BLM land. Used HY-8 to analyze the culvert (file attached). Now I'm looking at outlet protection. The design flow is 54-cfs (10-yr storm) but want to protect against the velocity for 129-cfs (25-year storm). The...
I'm designing an 8'x4.2'' open bottom arch culvert to be used in a stream with a 100-year flow of 147-cfs. I'm using HY-8 for the culvert analysis - a HEC-RAS model is beyond the scope of this project. The footers for the culvert have to extend about 4.5-ft down to get below frost depth and...
I'm working with a FEMA effective HEC-RAS model that uses contraction and expansion coefficients of 0.6 and 0.8 instead of 0.3 and 0.5 at some culverts. Chapter 5 of the manual shows that these values are used for "abrupt transitions". I have always thought that you used 0.3 and 0.5 for...
Running CHECK-RAS version 1.4 for the first time and have followed all installation and setup instructions to the letter. When I get to the extract data step I get the "Error: data extract" error message (I do not get the "checkras id <> csid" message).
I'm running HEC-RAS version 4.1.0 - my...
I'm trying to model an existing flood control structure in HEC-RAS in order to get the downstream flow for a floodplain study. The structure is immediately downstream of a double box culvert. It consists of a concrete channel with a weir on the left side and a rectangular orifice at the...
Here's the scenario:
36" CMP (maybe 20 years old or more) conveys a creek under a parking lot (FEMA 100-year flow =358-cfs). The CMP runs through a drop manhole so as to avoid water and sewer mains that run through the parking lot(about 4' drop - currently getting the survey done). The total...
I am in the final (hopefully) stages of a LOMR and the one thing that I'm getting hung up on is providing a "logical" horizontal tie in for the 500-year flood at the upstream cross-section in my study. The base flood ties in fine and the 500-year ties in on the left overbank but not the right...
