Drainage in Kentucky?

Doing a drainage report for some property in Boone County, Kentucky. Boone Co's regs say you can use TR-55 or some "Regional Method"...following is the wording from the regs:

>Regional Method of Bureau of Highways- all formulas, constants, and data shall be used with regard to the "Regional Method" from the Current Manual of Instruction of Drainage and Design, Ky. Transportation Cabinet, Bureau of Highways<

It has been "suggested" that I do both methods because this is for a court case.

I've checked all over Kentucky's website and can't find anything even referring to the "Regional Method" or any kinf of manual having anything to do with drainage. Anyone here familiar with any of this?

There talking about the Rational Method (Q=CiA).

Each portion of the storm water drainage collection system shall be capable of handling the peak flow of runoff. For drainage areas less than 200 acres, the method that shall be used is the "Rational Method." For areas greater than 200 acres, either the "Soil Conservation Service (SCS) Method" or the "Regional Method" of the Kentucky Transportation Cabinet, Bureau of Highways shall be used:

1. "Rational Method" where Q = CiA

Q = peak runoff quantity in cubic feet per second;

C = runoff coefficient varying with perviousness and other characteristics of the drainage area;

i = average intensity of precipitation in inches per hour, varying with frequency of storm occurrence, duration or concentration time, and area of the tributary watershed;

A = area in acres of the tributary watershed.

A. Runoff Coefficients: The runoff coefficient is the portion of the precipitation, expressed as a decimal, that will reach a given storm water facility. Each lot within a subdivision contributes runoff from the roof, driveway, sidewalk and street. Generally, the smaller the lot width, the less impervious area. As the lot increases in width so does the impervious area. Weighted coefficients shall be used with the impervious areas C = 0.95 and all other areas C = 0.40. Residential developments shall be calculated using lot impervious areas as follows:

See Boone County

for more information.

Jeb - I don't know if this is what they are referring to, but I did a study in McCracken ( :lmao: ) County and used this reference to find peak flows:

http://pubs.usgs.gov/wri/wri034180/pdf/wri034180.pdf

I don't remember seeing the words "Regional Method" but it was written for the KY Transportation Cabinet.

See Boone County
for more information.

Click to expand...

Been there...done that.

I've actually got Boone County's regs sitting in front of me. The thing that has me confused is the fact that they specifically refer to using the Rational Method for areas under 200 acres and the Regional Method for areas over 200 acres.

In the regs they also call out using the constants and formulas from the Manual of Instruction of Drainage and Design. If this is the same as the Rational Method, I'd still like to find something to make sure they're using the same constants and formulas as everyone else. I've already run into that a few times..."solve this by using the Rational Method, but here in Podunk County we decided to use this Intensity instead of the Intensity everyone else is using".

I thought the TR-55 was generally accepted universally.

When I do a drainage study, I get the desired rainfall data from the state guidance manual; physical parameters from the site plan, and just plug into HydroCad, which is based on the TR-55.

Both the states I work in have their quirks and occasionally have preferred values to use in the model rather than the programmed defaults, but they accept the output as an industry standard because TR-55 comes down from NRCS.

I've used the TR-55 method on sites ranging from 1 ac - 40 ac with no issues from regulators. They just rip my design instead!

What's this "rip my design" you speak of? That never happens to my stuff!?!?

The TR-55 stuff is done....this is just some CYA type stuff for the guy who is going to be defending this stuff in court.

Since the regs say to use TR-55 or the Regional Method he wants to do both in case someone wants to know why we didn't use that one instead and it ends up being way off from the TR-55 discharges.

I read it more closely and noticed that there is a difference and it isn't clearly spelled out.

However, Kentucky has some great Microstation drawings that I am going to convert using TurboCAD to AutoCAD.

Maybe they can clean up there regs to match this kind of quality.

If I remember right, when I did my study I was told that the USGS had been commissioned by KY Trans to determine these regression equations for the entire state. In the report the state was divided into several regions and there are regression equations for each region. These may be the constants and formulas you're looking for.

Okay, I started going through the report that Frazil posted on here...let me tell you, it is some exciting stuff.

Anyway, in the process of looking for some additional info, I managed to run across [SIZE=13pt]this[/SIZE] through Kentucky's USGS page. It's basically GIS info that lets you look up stream data for the entire state of Kentucky.

I hate to chance lowering my "cool engineer" status, but it is pretty cool. Now I just need to try and figure out why their numbers are so much different than my TR-55 numbers.

NY had a good site about that stuff. In VT you can get some stuff from the state GIS office, but it's more the names and locations of waterbodies than serious hydrologic data.

Cool site. You get an extra punch on your "cool engineer" card.