Hydraulics and Hydrology

Why are people using these forums for marketing? This is the second time this has happened to me. Both incidents have occurred recently.

You need geotextile to figure out your contours!!!

He's only trying to help.

It's a big subject you're undertaking. I would suggest a little survey for say a small parking lot and draw the contours by hand to get a feel for that process. Go to the field gather the data and draw them out.

As far as how hydraulics are figured for a watershed it's a process of calculating the area of the watershed, getting the historical amount of rainfall from tables for that area and then putting it through formulas to arrive at what is normally a BFE at our site for us.

But surveyors don't do that, that's all engineering. I have a guy on call who does it for me. He even sent me a spreadsheet that allows me to do the BFE calculations for, 100, 50, 25 year floods, all types of pipes, spillways, ect. It's quite awesome.

As far as grid intervals for contours, I'd rather use QUAD sheet contours, they are available on the NGS website and that's what we use for drainage reports submitted to the regulators. Again, my engineering partners sign off for that.

A watershed for a stream might be a couple of square miles or for New Orleans half the United States.

All I was told in school is that contour lines are "lines of same elevation" and that water flows perpendicular to contour lines at every point along them, both of which seemed completely obvious.

I have never heard of contours pointing uphill or downhill and this doesn't make sense to me. As far as I know the only way you know you're looking at a mountain or a hole is by the elevations on the lines.

As far as the contour interval to choose I suppose it depends on the grade of the slope and the scale of the drawing. For example, if you use a 1' interval on something with like an 80% grade you might end up with an unreadable blob of linework.

The really old school way to determine a watershed area is to start at the point of concentration and draw a continuous line that crosses each successive contour at right angles. Eventually you will end up back at your starting place having drawn an irregular figure.

There is no simple answer to hydrology. It is a complex situation dependent on a number of variables and "magic" numbers. Dig into the materials you have been provided. They must refer to the Universal Soil Loss Equation.

https://en.wikipedia.org/wiki/Universal_Soil_Loss_Equation

Each factor included in RKLSCP is very important and is only applicable to certain portions of the total watershed involved. The relative density of the material where the water falls, for example, has a major impact on time of concentration. Standard asphalt and concrete is incredibly different from a previously dry loamy soil. Vegetation density and height can represent a different challenge.

Learn it and learn it well, or it can bite you in the butt someday.

I am curious as to why you are studying this, aside from understanding contours. Stormwater management is not something that you can learn in a semester or two as there are many variables involved to include slopes, soil types, time of concentration and more to arrive at peak runoff rates.

Hydraulics and Hydrology are better left as an engineering function, the larger the water shed the more complicated it can become.

You will if you have not yet be learning Manning s equations. As stated before. Go Topo a parking lot on a 50’ ft grid. Take it back to the office have them print it to scale. Then get a scale. And start drawing contours by hand. Something my professor taught me was. You need to get the cow out of the pasture. So as you draw contours those lines cannot cross. They can circle back to themselves but not cross. So different states are different in this. But as a surveyor in some states you are able to do certain things in this realm of hydrology and or hydraulics. But mostly engineers do this. I wish you were closer. I have an old book from the military that would be awesome for teaching contours. Learn things like saddles and such. This would get you understanding up for sure. But the hand drawing will be one of the best things you can do. V and such can show ditches creeks or even the cl profile of a road. You will get it hang in there. I am going to take a couple classes just because it has been so many years since I truly studied this and here I can apply eventually for a surveyor B license which allows me to do more in the realm vs just a LS . The equations are scarier than it really is. Most of the numbers come from somewhere else. It’s all plug and play eventually. Grass vs asphalt vs concrete. Soil types like stated above. You got this.

You're right with the "pointing up/down" rule of thumb. For those that didn't get it right off, if the contours create a flow pattern (like multiple U's) that's either a valley or ridge formation depending on whether the multiple U's are point toward the next higher contour (a valley/stream) or pointing toward the next lower contour (a ridge). Watershed boundaries are defined by ridgelines. IE, if you were a drop of water and you landed on a ridge, which way would you runoff? Left of the ridge into a basin, point of confluence or stream/valley or to the right of the ridge ultimately into an entirely different basin, etc. A point of confluence usually (not always) defines the lowest watershed boundary point and many times is where an adjacent watershed stream joins it. Hydrology can become, IMO, very complex (so can hydraulics) where you have to evaluate mean slopes of areas within the watershed depending on their differing permeabilities - grasses/foliage types, soil types, coverage like pavement, rooves, bare dirt, rock, etc to come up with "first flush" which is developed into time of concentration (of waters to the confluence) and rainfall intensities. I do many grading plans and on some have to do a hydrologic study where, in my limited knowledge, I use the most fundamental "rational method" to get runoff values and place BMPs. Real engineers have many more complex ways of evaluating land to accurately determine when, how much and where. Sounds fun. I'd like a class like that. To get flow paths across land you can use Civil 3D on an existing and proposed surface to "drop water" along your ridgelines or boundaries an watch it create polyline that follows the flow from that point.

The Manning equation relates to pipe sizing, flow and slopes. Totally different than defining watersheds and peak runoff.

Yes for sure on manning equation. But it was part of the curriculum many years ago when I took a class. I went to a seminar last year that dealt with the water sheds. I realized. I needed more than a refresher for sure. I spoke with one of men that was teaching and he also teaches those classes for a college. Outside of his surveying job. So I will be taking those when the rotate back in. I have so much to learn and re learn. I think the OP will end up getting some valuable knowledge for sure. He is already asking the right questions.

Understanding contouring and other fundamentals are valuable things to grasp, but, who actually manually drafts them these days? If you know the basic concept and have the data to import or trace in C 3D, create your TINS and break lines, contour it with that information and hand the data off, what is the value of learning something from a seminar, aside from general knowledge, that you will probably never use as a surveyor?

One pet peeve of mine is finding contour maps that ignore the facts. One example is where a contour line hits a curb. The contour line needs to follow the curb line until the top of curb is finally reached.

@ Norman_Oklahoma

The really old school way to determine a watershed area is to start at the point of concentration and draw a continuous line that crosses each successive contour at right angles. Eventually you will end up back at your starting place having drawn an irregular figure.

Thanks.

@ james-fleming

Rule of v's.

Thanks. This is very helpful.