How do I calc 100 year elev for a creek?

In Indiana, where you're allowed to do all the engineering in a subdivision, I would use Streamstats (Google it) to determine the creeks watershed and discharge, and then Quick2 from FEMA to determine flood elevations.

It's not for the faint hearted, but this is the simplest approach I know of, unless there's been a newer bridge built over this creek near to your site. In that case, I would get the flood study information from the bridge engineer and save yourself a lot of work.

> I have a minor subdivision with a creek running through it that is over one mile from the nearest FEMA mapped 100 year flood.
>
> The locals want me to:
>
> • Show 100-year elevation of Travis Creek
> • Show minimum flood protection grades on all lots
>
> How do I do this?

Is the creek a designated Zone AE? Or is it a minor tributary running through a Zone X area?

Also, fwiw, the term 100-year flood is going out of style. A better way to describe that is a 1% chance of annual recurrence flood. If you had a 100 year flood a few years ago clients assume it will be another 100 years before that level of flood again. We know that isn't how things work, but most clients don't know that.

Larry P

Or of course, hire a hydraulics engineer to do it all for you.

Streamstats

We've used it several times around here. And interestingly, have had a couple of conversations with COE personnel in the Tulsa office about Streamstats. Seems as though when they are asked to determine flood characteristics (at a cost to the applicant) they also use this software.

Save your client $200.;-)

I would highly recommend hiring an engineer that specializes in this kind of work. Support their study with your field surveying and learn as you go.

However here are some resources....

Army Corp. of Engineers - FREE HYDRO TOOLS

USDA NRCS- WIN TR-55 small watershed hydro software- SOIL SURVEY DATA(Soils Types and Hydrologic Soil Subgroups

USGS - FREE QUADS (Drainage basins, stream reaches, and grades)

NOAA - RAINFALL DISTRIBUTION

LOCAL COUNTY - Drainage Manual

GOOGLE EARTH - LAND USE/COVER TYPES AND ACREAGES

Visiting the site on the ground is a must. Field cross sections, drainage structure measurements, interviews with long time residents, speak with the county maintenance crew about the historical flooding at drainage structures both upstream and downstream. What was the most recent flood of record, is there still debris evident along the stream? How about scarring on tree trunks?
There is a lot to it and some of it just comes down to experienced judgment. Does the answer the software is spitting out make sense?

PS, I would also speak with the state and county engineering department about any historical flood studies associated with nearby drainage structures. It's all part of the package of evidence that will allow you to sleep at night knowing peoples houses will not be flooded because of your work.

Be aware that what you describe brings with it very high liability. That high liability should also mean you are well compensated for the work. My guess is the client won't want to pay you what you should receive as just compensation. Minor subdivisions rarely have such a high profit margin that they can afford $15k, $20k or even $30k in extra survey expense.

Before you get too far into the details of "how" be sure and check with the client to see "how much" they had in mind to pay.

Larry P

Excessive land development requirements from the County/City Planning Department is something that the developer's representative (many times a land surveyor) should be on the look out for at the project's conception. These costs would be anticipated and factored in prior to deciding to commit to a project.

I can say with 100% certainty that the local Planner has zero regard for profit margins. If it is a condition of development, it's a cost of development.

If the property is clearly outside any flooding delineated on the FEMA mapping, perhaps a note stating such would fit the bill.

Really kind of depends on the site/situation.

Yes high liability - I say if specialized studies are required hire someone licensed to do that sort of work.

This is a little disturbing to read for somebody who is both a PE and PLS. A few thoughts to consider: In CT, this is clearly the practice engineering and if you practice engineering without a license, you'll put yourself in hot water. I'm not sure what your state statutes say, but probably something similar. Next, a true professional realizes that they don't know everything and you're not expected to...that's why you associate yourself with other professionals who can offer their expertise. You can get all the software in the world...if you don't understand what it's doing for you, you shouldn't be doing the work. It's no better than the "button pusher" surveyor.

An engineer has an ethical responsibility to protect the health, safety and welfare of the public and part of that is a responsibility not to practice in an area in which they're not competent. A surveyor should have the same sense of obligation, especially with something like determining a flood plain where you actually could endanger the public. Unless you're an engineer, don't try to practice engineering. If you have to ask how to do this, you're not qualified to do it. Find an engineer to work with and perhaps they'll teach you the basics of hydrology and hydraulics (that's how you diversify your competence, but remember that sureveyors shouldn't try to certify engineering work. How would you feel if an engineer asked you how they can perform a boundary survey and certify it? They could start by getting years of experience working under a licensed surveyor, then they could pass the PLS exam, and then they could perform their boundary survey and certify it.

The same is true here in Mississippi. Such determinations are outside of the expertise of a most surveyors and thus are not allowed. When you get these kind of requests (flood zone areas, wet lands determinations, etc.)the best thing to do is to inform the client that all of that lies within the realm of an engineer and that you can recommend someone.

Many thanks to all responses. A good thread, all in all. Here is the e-mail I sent to my client yesterday.

Say Client A, I am sorry for my recent wishy-washiness on this. But the Storm Water Board really has my head spinning with their approach on your project (a supposedly very simple straight forward minor plat with large rural lots), and now how they are backing up 2 years later on Client B’s already approved and recorded plat.

This is definitely ENGINERING, not engineering.

I cannot help address their comments for you or for Client B. I am a Land Surveyor.

This is Engineering work.

I urge you to reconsider Professional Engineer A's proposal (which I arranged for a month ago) and authorize him to proceed when you are ready to do so. I am going to introduce him to Client B to help with his side of these comments too.

Sorry for all the confusion on my part.

This small but rapidly growing Town "B" is definitely going through some growing pains, and they are taking us along for the ride.

Brad

"This small but rapidly growing Town "B" is definitely going through some growing pains, and they are taking us along for the ride."

Now's the time to make as many friends as you can in the Engineering, Planning, and Zoning Departments. Some call it "sucking up". Call it what you want but it can result in overcoming obstacles such as you have incurred without much ado. Maintaining an exemplary relationship with county/city employees is a pain in the ass but it has its benefits. Believe it.

Have a great week! B-)

“I would highly recommend hiring an engineer that specializes in this kind of work. Support their study with your field surveying and learn as you go. ”

“Yes high liability - I say if specialized studies are required hire someone licensed to do that sort of work.”

I understood that this post was under education, meaning someone wants to learn.
Sheesh!

I suspect that every licensed surveyor or engineer knows the limits of their field of study. It really goes without saying. Many here are dual licensed (PLS/PE).

Sage advice Squire.

Eons ago I studied hydrology in my surveying degree and Brad I would suggest that you introduce your client to an experienced hydrologist and fore go the peanuts and any future horrendous compensation claims.

RADU

In Indiana, a surveyor can do all the engineering within his subdivision.