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Area - Advanced Hydrology - Problems, Exercises of Engineering Dynamics

These are the Problems of Advanced Hydrology which includes Excess Ordinate, Data, Area Method, Histogram, Calculation, Contribution etc.Key important points are: Area, Method, Appropriate Shape, Duration Rainfall, Duration Of Rainfall, Small Watershed, Distributed

Typology: Exercises

2012/2013

Uploaded on 03/28/2013

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Use Snyder’s method to develop aUH for the area of 100mi2described below.
Sketch the appropriate shape.What duration rainfall does this correspond to?
Ct= 1.8, L= 18mi,
Cp= 0.6, Lc= 10mi
Calculate tp
tp= Ct(LLC)0.3
= 1.8(18·10)0.3 hr,
= 8.6 hr
Module 3
Example Problem
Synthetic unit hydrograph
Calculate Qp
Qp= 640(cp)(A)/tp
= 640(0.6)(100)/8.6
= 4465 cfs
Since this is a small watershed,
Tb 4tp = 4(8.6)
= 34.4 hr
Duration of rainfall
D= tp/5.5 hr
= 8.6/5.5 hr
= 1.6 hr
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Use Snyder’s method to develop a UH for the area of 100mi2 described below. Sketch the appropriate shape. What duration rainfall does this correspond to? Ct = 1.8, L= 18mi, Cp = 0.6, L (^) c= 10mi

Calculate t (^) p t (^) p = Ct (LL (^) C) 0. = 1.8(18·10) 0.3^ hr, = 8.6 hr

Example Problem

Synthetic unit hydrograph

Calculate Qp Qp = 640(c (^) p )(A)/t (^) p = 640(0.6)(100)/8. = 4465 cfs

Since this is a small watershed, Tb ≈4tp = 4(8.6) = 34.4 hr

Duration of rainfall D= t (^) p /5.5 hr = 8.6/5.5 hr = 1.6 hr Docsity.com

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0 5 10 15 20 25 30 35 40

Q (cfs

)

Time (hr)

Qp

W (^75)

W (^50) Area drawn to represent 1 in. of runoff over the watershed

W 75 = 440(Q (^) P/A) -1. W 50 = 770(Q (^) P/A) -1. (widths are distributed 1/3 before Q (^) p and 2/3 after)

Synthetic unit hydrograph

Example Problem Contd…

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Find TR using eq.

Given rainfall duration is 2 hr, TR = 4.36 hr, the rise of the hydrograph Then find Qp using the eq, given A= 10 mi 2

. Hence Qp = 1.110 cfs

Synthetic unit hydrograph

R

p

T

A

Q

R t p

D

T = +

To complete the graph, it is also necessary to know the time of fall B. The volume is known to be 1 in. of direct runoff over the watershed. So, Vol. = (10mi 2 ) (5280ft/mi) 2 (ac/43560ft 2 ) (1 in.) = 6400 ac-in Hence from eq.

B = 7.17 hr

Q T Q B

Vol

p R p

Example Problem Contd…

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0 2 4 6 8 10 12 14

Q (cfs

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Time (hr)

Qp = 1110 (cfs)

T (^) R=4.36 (hr) B=7.17 (hr)

Synthetic unit hydrograph

Example Problem Contd…

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  1. The ordinates of a 4-hour unit hydrograph for a particular basin are given below. Derive the ordinates of (i) the S-curve hydrograph, and (ii) the 2-hour unit hydrograph, and plot them, area of the basin is 630 km 2

Time (hr) Discharge (cumec) 0 0 2 25 4 100 6 160 8 190 10 170 12 110

Time (hr) Discharge (cumec) 14 70 16 30 18 20 20 6 22 1. 24 0

Exercise problems Contd…

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  1. The following are the ordinates of the 9-hour unit hydrograph for the entire catchment of the river Damodar up to Tenughat dam site: and the catchment characteristics are , A = 4480 km^2 , L = 318 km, L (^) ca = 198 km. Derive a 3-hour unit hydrograph for the catchment area of river Damodar up to the head of Tenughat reservoir, given the catchment characteristics as, A = 3780km^2 , L = 284 km, L (^) ca = 184km. Use Snyder’s approach with necessary modifications for the shape of the hydrograph.

Time (hr) 0 9 18 27 36 45 54 63 72 81 90

Flow (cumec)

Exercise problems Contd…

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