Determination of Concentration Time and Travel Time
Travel time (T_t) is the time of travel of water from one location to another in a watershed. T_t is a component of time of concentration T_c and T_c is the time for runoff to travel from the hydraulically most distant point of the watershed to a point of interest within the watershed. T_c is computed by summing all the T_t for consecutive components of the drainage conveyance system.

T_t is the ratio of flow length to flow velocity : -

where, T_t = travel time (hr)
L = flow length (ft)
V = average velocity (ft/s)
3600 = conversion from second to hours.

The average velocity (V), was computed by the Manning's equation :-
where, V = average velocity
r = hydraulic radius (ft) and is equal to a/p_w
a = cross sectional flow area (ft² )
p_w = wetted perimeter (ft).
S = slope of the hydraulic grade line (channel slope, ft/ft)
n = Manning's roughness coefficient for open channel flow.

The time of concentration (T_c) is the sum of T_tof the various consecutive flow segments,
T_c= T_t1+T_t2+……+ T_tm……………(7)
where, T_c = time of concentration (hr)
m = number of flow segment
T_t= travel time of a segment.

Table 5 shows the time of concentration for each watershed in the study area.
TABLE 5. The concentration time for each watershed

Watershed	Area (mi2)	Flow Length (ft)	Concentration Time (hr)
Wt1	12.2709	31576.1455	3.4115
Wt2	17.2671	43649.0935	5.2616
Wt3	5.2742	19134.815	2.2029
Wt4	6.5450	22340.1859	2.6725
Wt5	35.8262	52883.9475	4.79074
Wt6	9.5793	39302.9858	4.0881
Wt7	1.3066	10667.9244	0.41365
Wt8	7.6330	34744.5461	2.40227
Wt9	1.3368	12939.6384	0.57828
Wt10	19.5362	52520.3703	4.49168
Wt11	1.7229	7979.3706	0.54646
Wt12	7.6503	37255.777	1.59095
Wt13	12.3727	35040.8425	3.5393
Wt14	59.0031	62278.0685	6.76384
Wt15	29.0425	59213.6906	5.16663
Wt16	25.7438	90815.7426	6.47327
Wt17	21.0961	90815.7426	3.79186
Wt18	32.2196	58721.3330	6.95108
Wt19	28.8111	36803.7179	3.85335
Wt20	25.52	50864.0234	6.29147
Wt21	38.0265	86440.2044	0.62849
Wt22	117.4947	73481.3778	0.32320
Wt23	2.6712	14059.0118	1.09378

Determination of Peak Discharge
The peak discharge was determined by SCS TR-55 graphical method. In this method, the peak discharge is calculated by : -
q_p= q_u A_m QFp …………………(8)
where, q_p = peak discharge (cfs)
q_u= unit peak discharge
A_m = drainage area (mi²)
Q = runoff (in)
Fp = pond and swamp adjustment factor.

The results of the peak discharge for each watershed are presented in Table 6.

Determination of Bankfull Discharge
The bankfull discharge was determined using the slope area method. In this method the equation that was used is : -
Q_b=KÖ S ……………………(9)
where, Q_b = bankfull discharge
K = average conveyance
ÖS = slope energy

K is defined by Manning's formula as: -

where, A = cross sectional flow area (ft² )
R = hydraulic radius
n = Manning's roughness coefficient