Question 1 - Problem 508
Units not shown, I hate it when they do that.
A Unit Hydrograph is a hydrograph of of dropping 1 inch evenly on the watershed. You get it by dividing every point on the hydrograph by the average excess precipitation. So, where they hydrograph Q has units of cf/s, a unit hydrograph has units of cf/(s x in).
Draw out the unit hydrograph with the 3 points given. It goes up and down over a course of 3 hours. The values are:
Q1=0.5cf/(s x in)
Q2=1.2cf/(s x in)
Q3=0.4cf/(s x in)
Now, the first hour you are given values in inch/hour. The rain events last 1 hour.
0.5 in/hr x 1 hour = 1.5 in
0.7 in/hr x 1 hour = 0.7 in
Now multiply for the first two hours, as asked for in the problem:
0.5cf/(s x in) x 1.5 in + 1.2cf/(s x in) x 0.7 in =
Now that should help you with your units, as you can see you'd wind up with cf/s. However, to get the answer they did you would need to multiply 1.5x1.2 + .7x.5 = 2.15. Are you sure you wrote the question up correctly?
Question 1 - Problem 509
Read through Step 3, page 20-16. It appears that you need 'additional tables' for pasture land. Table 20-5 is specified for cultivated land.
I'm taking Transportation, so am only learning enough to get through the morning breadth. Hopefully won't need to worry about the extra tables.
