Hydrology report

[nagatalluri]

Guys:

Can you please educate me on the Hydrology reports. We received a hydrology report for a wind project. HydroCAD was used to model a 25 year flood event. Culvert calculations were provided in the report.

If I want to check the report can you tell me what to look for specifically/ in general in a hydrology report?

I appreciate your time

Thanks
NT

 

[beej67]

What are you "checking" in the report?

A complete hydrology report should have the following information:

Project Summary.
Discussion of the relevant design criteria, and how the project will meet that criteria.
Narrative and graphical depiction of the existing conditions of the site.
Narrative and graphical depiction of the proposed conditions of the site.
Basin maps for both of the above, with hydrologic characterizations of each.
Climate data to set the design storms
Runoff calculations by a responsible and regulatory approved methodology
Routing of any storage structures, as designed on a set of construction plans (review in tandem)
Hydraulic calculations as necessary for stormwater conveyance appurtenances in the project.
Results tables / summary.

In the last 15 years, these have started to be added as well..

Water quality calculations
Operations and Maintenance plans for stormwater features
Downstream / regional analysis

What goes into a report varies widely by region, as do the accepted methodologies for the calculations.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[brandonbw]

You would look to see if the proposed design can handle the 25-year storm Q? Why are you checking the report?

B+W Engineering and Design
Los Angeles Civil Engineer and Structural Engineer

http://bwengr.com

 

[nagatalluri]

We received the hydrology report (with the 25 yr. storm water calculations and the proposed culverts for the project access roads) from the contractor who works on the wind project we own. I was asked to review the report. I am curious about what to look for in a complete hydrology report.

Thanks
NT

 

[nagatalluri]

Dear beej67

Thanks for the input. This information is really helpful for a person who reviewed the report for the first time.

NT

 

[darthsoilsguy2]

note on language... generally the term "flood" is reserved for the 100-year storm because that is the FEMA flood map.... or at least that's how people i know use.

You should understand there are high-intensity/moderate-volume/short-duration 25 year storms and low-intensity/large-volume/long-duration 25-year storms, plus many storms in between. Generally speaking, a good design is checked to both types of storms. i would suspect a storm in your study is the "25-year, 24-hour storm".

 

[nagatalluri]

Yes it is, 25 year, 24 hour storm. Do you think it is better to include the 100-year storm as well?

 

[darthsoilsguy2]

i assume this is a design/build road otherwise the contractor wouldn't be modeling, and that your company issued that RFP or is CMing it. that being the case, i would just review the design requirements for storms they were supposed to design to as specified and then again according to state regs and hopefully find no conflicts in the original specifying document (or confirm that the specs were drafted to meet/exceed state regs). since you've been given the task by your boss, you could look at the storms are for the location and maybe understand it better. a very common resource link used is below.

http://www.nws.noaa.gov/oh/hdsc/index.html

i don't know anything about your project to say whether 100-yr storm would be appropriate, except that given its a wind farm, you're probably not in a flood plain. i personally find very few occasions to model 100 years, but mine are usually subdivisions and commercial.... i would be more interested in seeing how the system behaves under a 10-yr 5-min storm (selecting arbitrarily). there are actually a lot of tricks that someone can do to cook the books for stormwater modeling in Hydrocad or any other software. if the time of concentration is BS, the modeling is BS regardless of the storm. If it really needs to be reviewed professionally and not just administratively, get a local site design CE and learn in the process.... By the way, there is a storm/flood forum on this site.

 

[cvg]

a few things to watch for

a) make sure your roads or culverts or anything else you are constructing does not divert runoff from the natural flow path to another path. that can cause downstream impacts to other property owners.

b) make sure your construction does not back up water and cause ponding which would affect any adjacent or upstream properties.

c) if you are in the United States, than you need to check FEMA flood insurance rate maps to determine if you are in a regulatory floodplain which is generally 100-year. just because this is a wind project has no bearing on if the road crosses a floodplain.

d) you may need calculations for erosion and sediment deposition especially at culverts and ditches

e) i assume you will need an all weather access road to the site. generally these are designed so that they are passable by emergency equipment during 100-year conditions.

 

[nagatalluri]

Sir

Thanks for the input. It is indeed very helpful

NT