Water Resources-Rational Method

[@davidperalta7]

According to the NCEES Handbook, it is not necessary to change units. If you have the area (acres), intensity (in/hr), then the answer will be in Q (cfs). So, Q= 0.81*0.8*12 = 7.77 cfs

[@do3a2e]

actually you don't have to convert anything its already being done by the equation it self .. if you need the answer in cfc you have to make sure that the (A) by acres and (I) by in/hr and (C) is unitless and the (K) will do the conversion for you which is in this case equals to 1. "Q=KCIA" please correct me if am wrong . GOOD WORK

[@CivilEngAcademy]

Peaceful mind Yes this is right. Thanks for the comments!! I hope that by generating good questions and comments they will benefit others so thanks!

[@svongsa]

PEACEFUL MIND yes, no unit conversion necessary! Good!

[@TheVahane]

@@CivilEngAcademy take this video down. It is misleading. Q=CiA the native output is cfs. You don't need to convert anything. Please do yourself and the program a favor and take it down.

[@DeagleBeagle]

What dies the K stand for? Seems like Q = CIA will solve it

[@Erupit2]

Technically we do convert, but the conversion factor is 1.008, so it's usually ignored. You will find versions of this equation written as Q = nCIA, where n = 1.008

[@senudarajapakse3469]

that line to 0.8 on the y-axis is very poorly drawn. I assumed 1 for I because of that. The example/instructor needs to be more clear

[@mchlgrffn88]

Please note that time of concentration is not the same as duration. Duration of an event upstream from the outflow point can often be miles away in civil engineering. I would also take a look at detention pond design as the t sub c can be increased for runoff mitigation as durations may often be short. Please let me know if I have not thought about this correctly.

[@HipperTea]

I know I'm a decade late, but to explain for others: one condition of the rational method is that the storm duration is equal to the time of concentration, so in this problem it means the same thing. If you were using the NRCS (formerly SCS) method, you would be correct that the duration would not equal the time of concentration.

[@oleopathic]

Ncees pe hb 1.1, p. 376. No conversions needed. Eqn takes care of it all.

[@The.Ch0senJuan]

Man this guy's screws up a ton. I'm done watching these. It's going to hurt me more than it helps me

[@mther123]

good, keeping going on

[@CivilEngAcademy]

Thanks!

[@gullrahmanafzali4457]

v. useful keep going

[@georgehanna8768]

The answer is d) since the equation Q =CIA works out the units so that I (intensity) needs to be in/hr, not in/sec. This is the second wrong answer I have seen in this video series. TAKE CAUTION AND CHECK HIS WORK. This is the second wrong answer I have seen so far. I recommend doing practice problems in books.

[@johncole5175]

"Unit conversion from acre-in./hr to ft3/sec is most often approximated to 1.0." from the CBT PDF. Save a few secs...