What is the probability that a $25-$year return frequency storm will be exceeded in any given year?

A $12-$acre parcel of land is comprised of $8$ acres for a school campus $($average ground slope of

and $4$ acres of forest $($average ground slope of $7\%).$ What value most closely depicts the weighted

Rational C coefficient for the entire parcel?

A $33-$acre watershed consists of a residential subdivision with $1/4$ acre lots underlain by Hydrologic

Soil Group $($HSG$)$ C$.$ Using SCS runoff methodology, compute the watershed's initial

abstraction $(I_A),$ potential maximum retention $(S)$ and runoff depth $(Q)$ for a $2-$year, $24-$hour

precipitation depth of $3\mathrm{.}60$ inches.

The pre and post$-$development characteristics of a particular watershed are described as follows:

Assuming a Type II rainfall distribution, and a $10-$year, $24-$hour precipitation depth of $4\mathrm{.}25$ inches,

use Chapter $6$ of TR$-55$ to estimate the detention volume required to return the post$-$development

runoff rate to its pre$-$development level.

The flow path from a watershed's outlet to the hydraulically most remote point in the watershed is

made up of the three segments described below:

$120$ feet of overland flow across dense grass $(3\%$ ground slope$)$

$250$ feet of shallow concentrated flow across a paved surface $(5\%$ ground slope$)$

$750$ feet through a new concrete $24"$ pipe and placed on a $2\mathrm{.}1\%$ slope. You may assume half full

flow conditions. Use Hydraflow Express $($compute by known depth, depth $=1\mathrm{.}00\text{'})$ or the pipe

nomograph to determine the velocity of a half$-$full pipe. Provide a copy of the annotated

nomograph or Hydraflow Express output with your calculations.

Compute the watershed's time of concentration by hand using the methods discussed in class and the

equations available in the VDOT Drainage Manual Chapter $6($Appendix $6$D$-1$ and $6$D$-6).$