0-6382
Establish Effective Lower Bounds of Watershed Slope for Traditional Hydrologic Methods
Summary of TTI Task between 9/15/2009 to 12/31/2009
Ming-Han Li and Young-Jae Yi
2/19/2010
This summary documents the data collection and treatment processes conducted by the TTI team.
In this period from 9/15/2009 to 12/31/2009, we collected eight samples from outdoor concrete
runway and six from outdoor grass field. No indoor tests were conducted. Major experiments
include two outdoor sites (concrete and grass surface each) and one indoor test bed. Outdoor
tests are passive monitoring of natural rainfalls while indoor ones are conducted using an
artificial rainfall simulator.
Investigating the measurement error that total discharge volume exceeded total rainfall volume in
some previous samples, we found out that our ISCO tipping bucket rain gauges usually
underestimate the rainfall volume.
This summary provides a brief analysis of the problem and describes how we attempt to correct
the errors.
Outdoor test site on grass surface
The test site on grass is located at TAMU Riverside campus. The area is 5000 ft2 (100’ × 50’)
bordered by soil berms in 7-inch height. The slope is overall 0.5% (see Figure 1). We regularly
mow the site to maintain grass height between 4 and 8 inches.
<---------- 50' -------->
<------------------------------ 100’ ------------------------->
0.000
0.208
0.292
0.083
0.313
0.021
0.125
0.253
0.208
0.292
0.229
0.292
0.333
0.646
0.563
Figure 1: Survey of outdoor grass site [(values indicate the elevation differences from the
outlet (0.000) in foot]
Figure 2: H-flume installed on outdoor grass site
Adjusting underestimates of rainfall rate
Problem
We found measurement errors from some rainfall events, in which the total discharge volume
exceeded the total rainfall volume. Figure 3 shows an example. We adjusted the discharge depth
values to be reasonable before calculating the discharge volume (e.g., setting the depth value
zero in a dry condition).
Cumulative volume of rainfall and discharge
Cumulative volume (cf)
800
700
600
500
400
300
200
Rainfall
100
Discharge
22:50
22:20
21:50
21:20
20:50
20:20
19:50
19:20
18:50
18:20
17:50
17:20
0
Figure 3: A measurement error -- cumulative volume of discharge exceeds cumulative
volume of rainfall.
Possible reasons and how to deal with each of them
1. Discharge from the outside of the test field:
We checked if there was any damage on the boundary berm. No such case was observed.
2. Discharge measurement errors by flow meter:
We compared the flow meter readings recorded by the ISCO flow meter with visual readings
of a ruler engraved in the H-flume. Most errors occurred in a dry condition for unknown
reasons (e.g., reading up to 0.033 ft for zero discharge), while readings in a flowing
condition were reasonably accurate. In our observations, discharge hydrographs responded
well to the change of rainfall intensity. We subtracted any readings recorded in a dry
condition as base flow.
3. Rainfall measurement errors by rain gauge:
A container rain gauge was installed to compare total rainfall volumes with our ISCO tipping
bucket gauge. The resolution of the container rain gauge is coarse at 1 mm and each reading
was taken after a series of successive rainfall events in one or two days. To date four
readings are recorded. We are also comparing the readings of our tipping bucket gauge to the
ones of a weather station about one mile away from our test sites. The weather station uses
‘Davis Vantage PRO2’ that provides cumulative rainfall volumes every ten minutes in real
time. Figure 4 shows the rain gauges we are using. We calculate total rainfall volumes by
summing up a set of consecutive rainfall events in one or two days. By far, we have gotten
sixteen measures by each gauge during 9/15/2009 to 12/31/2009. The comparison reveals the
systematic underestimates by our tipping buckets.
Figure 4: Rain gauges – container type, ISCO tipping-bucket and Davis weather station
We have been investigating the relationship between our rainfall data (from tipping bucket and
container rain gauge) and the weather station data to examine the possible errors (Figure 5). The
comparison shows the systematic underestimation by our tipping bucket while container gauge
data seem to well agree with the weather station data.
Rainfall volume measured by ours
(in)
Difference of total rainfall volume measures
between our guages (TB & container) and weather station
3.5
3.0
2.5
2.0
TB
y = 0.9826x
R2 = 0.9963
1.5
Container
y = 0.7208x
R2 = 0.958
1.0
0.5
0.0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Rainfall volume measured by weather station (in)
Figure 5: Correlation of rainfall volume calculated from our gauges with the volume
measured by weather station near our test sites – Tipping bucket (TB) gauge readings show
systematic underestimation.
The R-square between tipping bucket gauge and weather station is 0.958. The random errors
could be attributed to multiple factors, including different location between tipping bucket gauge
and weather station, different rainfall durations among sample precipitation volumes,
measurement errors by the weather station, and other well-known natural effects like evaporation
and wind. One minute of our higher data reading frequency is also found to be a source of
significant error in rainfall rate estimation especially at low rain rates1. The study suggests the
error becomes negligible with time scales longer than 15 min (Figure 6), but we will lose details
if choosing such a longer reading interval.
Figure 6: Tipping-bucket error for three time scales: 1, 5, and 15 min using 0.01 in tipping
bucket (Habib et al. 2001).
We adjust the underestimated rainfalls simply by dividing our rainfall data by the slope of
regression line, 0.7208, instead of using dynamic calibration which controls tipping errors by
rainfall rate. The simple adjustment based on total rainfall volume is still useful for our study
since the most of our cases have low rainfall rate (<0.84 in/hr = 0.6 / 0.7208) where measurement
errors are mostly attributed to short reading interval and natural factors rather than rainfall
intensity. Figure 7 shows two examples before and after rainfalls are adjusted.
1
Habib , E., Krajewski, W.F., and A. Kruger, 2001. Sampling errors of tipping-bucket rain gauge
measurements, ASCE Journal of Hydrologic Engineering, 6(2), 159-166.
100
80
70
60
50
40
30
20
Rainfall
10
Discharge
0
20
9/24/2009
Figure 7: Cumulative volumes of rainfall and discharge before and after rainfall rate
adjustment – the adjustment solves the problem of rainfall-discharge volume mismatch.
7:30
200
7:00
Discharge
6:30
6:00
5:30
5:00
4:30
4:00
0
3:30
Rainfall
3:00
400
2:30
1000
2:00
1000
1:30
600
1:00
1200
Cumulative volume (cf)
800
Cumulative volume (cf)
7:30
7:00
200
6:30
6:00
5:30
5:00
4:30
4:00
3:30
3:00
2:30
2:00
1:30
1:00
Cumulative volume (cf)
1200
16:10
16:40
17:10
17:40
18:10
18:40
19:10
19:40
20:10
20:40
21:10
21:40
22:10
22:40
23:10
23:40
0:10
0:40
1:10
1:40
16:10
16:40
17:10
17:40
18:10
18:40
19:10
19:40
20:10
20:40
21:10
21:40
22:10
22:40
23:10
23:40
0:10
0:40
1:10
1:40
Cumulative volume (cf)
Before rainfall adjustment
After rainfall adjustment
800
600
400
Rainfall
0
Discharge
4/25/2009
90
120
100
80
60
40
Rainfall
0
Discharge
Results
Outdoor tests on concrete surface (5-minute Intervals)
 Date: 4/12/2009
 Max. rainfall intensity: 1.68 in/hr
 Peak discharge: 0.027 cfs
Rainfall intensity and discharge flow rate
0.030
Rainfall
0.025
Discharge
13:00
0.000
12:30
0.00
12:00
0.005
11:30
0.02
11:00
0.010
10:30
0.04
10:00
0.015
9:30
0.06
9:00
0.020
8:30
0.08
8:00
Precipitation (in)
0.10
Discharge flow rate (cfs)
0.12
Cumulative volume of rainfall and discharge
Cumulative volume (cf)
160
140
120
100
80
60
40
Rainfall
20
Discharge
13:00
12:30
12:00
11:30
11:00
10:30
10:00
9:30
9:00
8:30
8:00
0
Figure 8: Outdoor test on concrete surface (5-minute interval), Apr. 12, 2009
 Date: 4/17/2009
 Max. rainfall intensity: 5.04 in/hr
 Peak discharge: 0.111 cfs
Rainfall intensity and discharge flow rate
0.25
0.12
Precipitation (in)
0.20
Discharge
0.10
0.08
0.15
0.06
0.10
0.04
0.05
0.02
0.00
10:30
11:00
11:30
12:00
12:30
13:00
13:30
14:00
14:30
15:00
15:30
16:00
16:30
17:00
17:30
18:00
18:30
19:00
19:30
20:00
20:30
20:30
0.00
Discharge flow rate (cfs)
Rainfall
Cumulative volume of rainfall and discharge
1800
Cumulative volume (cf)
1600
1400
1200
1000
800
600
400
200
Rainfall
Discharge
10:30
11:00
11:30
12:00
12:30
13:00
13:30
14:00
14:30
15:00
15:30
16:00
16:30
17:00
17:30
18:00
18:30
19:00
19:30
20:00
20:30
20:30
0
Figure 9: Outdoor test on concrete surface (5-minute interval), Apr. 17, 2009
 Date: 4/18/2009
 Max. rainfall intensity: 2.52 in/hr
 Peak discharge: 0.022 cfs
Rainfall intensity and discharge flow rate
0.12
0.03
Precipitation (in)
0.10
Discharge
0.02
0.08
0.02
0.06
0.01
0.04
0.01
0.02
13:10
12:40
12:10
11:40
11:10
10:40
10:10
9:40
9:10
8:40
8:10
7:40
0.00
7:10
0.00
Discharge flow rate (cfs)
Rainfall
Cumulative volume of rainfall and discharge
Cumulative volume (cf)
400
350
300
250
200
150
100
Rainfall
50
Discharge
13:10
12:40
12:10
11:40
11:10
10:40
10:10
9:40
9:10
8:40
8:10
7:40
7:10
0
Figure 10: Outdoor test on concrete surface (5-minute interval), Apr. 18, 2009
 Date: 4/25/2009
 Max. rainfall intensity: 6.72 in/hr
 Peak discharge: 0.087 cfs
Rainfall intensity and discharge flow rate
Precipitation (in)
0.30
0.10
Rainfall
0.09
Discharge
0.08
0.25
0.07
0.20
0.06
0.05
0.15
0.04
0.10
0.03
0.02
0.05
Discharge rate (cfs)
0.35
0.01
0.00
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
5:00
5:30
6:00
6:30
7:00
7:30
8:00
8:30
9:00
9:30
10:00
10:30
0.00
Cumulative volume of rainfall and discharge
Cumulative volume (cf)
1200
1000
800
600
400
200
Rainfall
Discharge
1:00
1:30
2:00
2:30
3:00
3:30
4:00
4:30
5:00
5:30
6:00
6:30
7:00
7:30
8:00
8:30
9:00
9:30
10:00
10:30
0
Figure 11: Outdoor test on concrete surface (5-minute interval), Apr. 25, 2009
 Date: 4/27~28/2009
 Max. rainfall intensity: .84 in/hr
 Peak discharge: 0.011 cfs
Rainfall intensity and discharge flow rate
0.012
0.040
Rainfall
0.035
Discharge
0.030
0.010
0.008
0.025
0.006
0.020
0.015
0.004
0.010
Discharge rate (cfs)
Precipitation (in)
0.045
0.002
0.005
0.000
15:40
16:10
16:40
17:10
17:40
18:10
18:40
19:10
19:40
20:10
20:40
21:10
21:40
22:10
22:40
23:10
23:40
0:10
0:40
1:10
1:40
2:10
2:40
3:10
0.000
Cumulative volume of rainfall and discharge
140
Rainfall volume (cf)
120
100
80
60
40
20
Rainfall
Discharge
15:40
16:10
16:40
17:10
17:40
18:10
18:40
19:10
19:40
20:10
20:40
21:10
21:40
22:10
22:40
23:10
23:40
0:10
0:40
1:10
1:40
2:10
2:40
3:10
0
Figure 12: Outdoor test on concrete surface (5-minute interval), Apr. 27~28, 2009
 Date: 4/28/2009
 Max. rainfall intensity: 3.36 in/hr
 Peak discharge: 0.026 cfs
Rainfall intensity and discharge flow rate
0.14
Rainfall
0.10
0.025
0.020
0.08
0.015
0.06
0.010
0.04
0.02
0.005
0.00
0.000
Discharge rate (cfs)
Discharge
3:30
4:00
4:30
5:00
5:30
6:00
6:30
7:00
7:30
8:00
8:30
9:00
9:30
10:00
10:30
11:00
11:30
12:00
12:30
13:00
13:30
14:00
14:30
15:00
15:30
Precipitation (in)
0.12
0.030
Cumulative volume of rainfall and discharge
200
Rainfall volume (cf)
180
160
140
120
100
80
60
40
Rainfall
20
Discharge
3:30
4:00
4:30
5:00
5:30
6:00
6:30
7:00
7:30
8:00
8:30
9:00
9:30
10:00
10:30
11:00
11:30
12:00
12:30
13:00
13:30
14:00
14:30
15:00
15:30
0
Figure 13: Outdoor test on concrete surface (5-minute interval), Apr. 28, 2009
 Date: 7/20/2009
 Max. rainfall intensity: 4.20 in/hr
 Peak discharge: 0.097 cfs
Rainfall intensity and discharge flow rate
0.30
0.120
Rainfall
1:20
0:50
0:20
0.000
23:50
0.00
23:20
0.020
22:50
0.05
22:20
0.040
21:50
0.10
21:20
0.060
20:50
0.15
20:20
0.080
19:50
0.20
Discharge rate (cfs)
0.100
Discharge
19:20
Precipitation (in)
0.25
Cumulative volume of rainfall and discharge
800
Rainfall volume (cf)
700
600
500
400
300
200
Rainfall
100
Discharge
1:20
0:50
0:20
23:50
23:20
22:50
22:20
21:50
21:20
20:50
20:20
19:50
19:20
0
Figure 14: Outdoor test on concrete surface (5-minute interval), Jul. 20, 2009
 Date: 9/10/2009
 Max. rainfall intensity: 5.04 in/hr
 Peak discharge: 0.066 cfs
Rainfall intensity and discharge flow rate
0.25
0.070
Rainfall
0.050
0.15
0.040
0.10
0.030
0.020
0.05
Discharge rate (cfs)
Precipitation (in)
0.060
Discharge
0.20
0.010
1:20
0:50
0:20
23:50
23:20
22:50
0.000
22:20
0.00
Cumulative volume of rainfall and discharge
300
Rainfall volume (cf)
250
200
150
100
Rainfall
50
Discharge
1:20
0:50
0:20
23:50
23:20
22:50
22:20
0
Figure 15: Outdoor test on concrete surface (5-minute interval), Sep. 10, 2009
 Date: 9/11~12/2009
 Max. rainfall intensity: 1.68 in/hr
 Peak discharge: 0.026 cfs
Rainfall intensity and discharge flow rate
0.060
0.030
Rainfall
0.025
0.040
0.020
0.030
0.015
0.020
0.010
0.010
0.005
0.000
0.000
Discharge rate (cfs)
Discharge
15:10
15:40
16:10
16:40
17:10
17:40
18:10
18:40
19:10
19:40
20:10
20:40
21:10
21:40
22:10
22:40
23:10
23:40
0:10
0:40
1:10
1:40
2:10
2:40
3:10
3:40
4:10
4:40
5:10
5:40
6:10
6:40
7:10
7:40
8:10
Precipitation (in)
0.050
Cumulative volume of rainfall and discharge
700
Rainfall volume (cf)
600
500
400
300
200
100
Rainfall
Discharge
15:10
15:40
16:10
16:40
17:10
17:40
18:10
18:40
19:10
19:40
20:10
20:40
21:10
21:40
22:10
22:40
23:10
23:40
0:10
0:40
1:10
1:40
2:10
2:40
3:10
3:40
4:10
4:40
5:10
5:40
6:10
6:40
7:10
7:40
8:10
0
Figure 16: Outdoor test on concrete surface (5-minute interval), Sep. 11~12, 2009
 Date: 9/13/2009
 Max. rainfall intensity: 5.04 in/hr
 Peak discharge: 0.088 cfs
Rainfall intensity and discharge flow rate
0.090
0.30
Rainfall
0.080
Discharge
0.070
0.060
0.25
0.050
0.20
0.040
0.15
0.030
11:40
11:10
10:40
10:10
9:40
9:10
8:40
8:10
0.000
7:40
0.00
7:10
0.010
6:40
0.05
6:10
0.020
5:40
0.10
5:10
Precipitation (in)
0.35
Discharge rate (cfs)
0.40
Cumulative volume of rainfall and discharge
700
Rainfall volume (cf)
600
500
400
300
200
Rainfall
100
Discharge
11:40
11:10
10:40
10:10
9:40
9:10
8:40
8:10
7:40
7:10
6:40
6:10
5:40
5:10
0
Figure 17: Outdoor test on concrete surface (5-minute interval), Sep. 13, 2009
 Date: 9/23~24/2009
 Max. rainfall intensity: 0.84 in/hr
 Peak discharge: 0.008 cfs
Rainfall intensity and discharge flow rate
0.009
0.01
Rainfall
0.008
Discharge
0.007
0.006
0.01
0.005
0.01
0.004
0.01
0.003
0.00
0.002
0.00
0.001
0.00
0.000
19:10
20:10
21:10
22:10
23:10
0:10
1:10
2:10
3:10
4:10
5:10
6:10
7:10
8:10
9:10
10:10
11:10
12:10
13:10
14:10
Precipitation (in)
0.01
Discharge rate (cfs)
0.02
Cumulative volume of rainfall and discharge
120
Rainfall volume (cf)
100
80
60
40
Rainfall
20
Discharge
6:10
7:10
8:10
9:10
10:10
11:10
12:10
13:10
14:10
19:10
20:10
21:10
22:10
23:10
0:10
1:10
2:10
3:10
4:10
5:10
0
Figure 18: Outdoor test on concrete surface (5-minute interval), Sept. 23~24, 2009
 Date: 9/24/2009
 Max. rainfall intensity: 0.84 in/hr
 Peak discharge: 0.014 cfs
Rainfall intensity and discharge flow rate
0.016
0.040
Rainfall
0.035
Discharge
0.030
0.012
0.010
0.025
0.008
0.020
0.006
0.015
0.010
0.004
0.005
0.002
0.000
0.000
Discharge rate (cfs)
0.014
18:10
18:40
19:10
19:40
20:10
20:40
21:10
21:40
22:10
22:40
23:10
23:40
0:10
0:40
1:10
1:40
2:10
Precipitation (in)
0.045
Cumulative volume of rainfall and discharge
120
Rainfall volume (cf)
100
80
60
40
Rainfall
20
Discharge
2:10
1:40
1:10
0:40
0:10
23:40
23:10
22:40
22:10
21:40
21:10
20:40
20:10
19:40
19:10
18:40
18:10
0
Figure 19: Outdoor test on concrete surface (5-minute interval), Sept. 24, 2009
 Date: 10/9/2009
 Max. rainfall intensity: 2.52 in/hr
 Peak discharge: 0.070 cfs
Rainfall intensity and discharge flow rate
0.070
0.18
Rainfall
0.16
Discharge
0.060
0.14
0.050
0.12
0.040
0.10
0.08
0.030
0.06
0.020
0.04
Discharge rate (cfs)
Precipitation (in)
0.20
0.010
0.02
0.000
6:50
7:20
7:50
8:20
8:50
9:20
9:50
10:20
10:50
11:20
11:50
12:20
12:50
13:20
13:50
14:20
14:50
15:20
15:50
16:20
16:50
17:20
17:50
18:20
18:50
19:20
19:50
20:20
20:50
21:20
0.00
Cumulative volume of rainfall and discharge
1000
800
Discharge volume (cf)
Rainfall volume (cf)
900
700
600
500
400
300
200
Rainfall
100
Discharge
14:50
14:20
13:50
13:20
12:50
12:20
11:50
11:20
10:50
10:20
9:50
9:20
8:50
8:20
7:50
7:20
6:50
0
Figure 20: Outdoor test on concrete surface (5-minute interval), Oct. 9, 2009
 Date: 10/11/2009
 Max. rainfall intensity: 1.68 in/hr
 Peak discharge: 0.018 cfs
Rainfall intensity and discharge flow rate
0.08
Rainfall
0.018
0.07
Discharge
0.016
0.014
0.06
0.012
0.05
0.010
0.04
0.008
0.03
0.006
0.02
0.004
0.01
0.002
0.00
0.000
Discharge rate (cfs)
0.020
11:35
12:35
13:35
14:35
15:35
16:35
17:35
18:35
19:35
20:35
21:35
22:35
23:35
0:35
1:35
2:35
3:35
4:35
5:35
6:35
7:35
8:35
9:35
10:35
11:35
12:35
Precipitation (in)
0.09
Cumulative volume of rainfall and discharge
Rainfall volume (cf)
250
200
150
100
50
Rainfall
Discharge
11:35
12:35
13:35
14:35
15:35
16:35
17:35
18:35
19:35
20:35
21:35
22:35
23:35
0:35
1:35
2:35
3:35
4:35
5:35
6:35
7:35
8:35
9:35
10:35
11:35
12:35
0
Figure 21: Outdoor test on concrete surface (5-minute interval), Oct. 11, 2009
 Date: 10/13/2009
 Max. rainfall intensity: 5.04 in/hr
 Peak discharge: 0.080 cfs
Rainfall intensity and discharge flow rate
Precipitation (in)
0.25
0.090
Rainfall
0.080
Discharge
0.070
0.20
0.060
0.050
0.15
0.040
0.10
0.030
0.020
0.05
Discharge rate (cfs)
0.30
0.010
0.000
12:00
13:00
14:00
15:00
16:00
17:00
18:00
19:00
20:00
21:00
22:00
23:00
0:00
1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
9:00
10:00
0.00
Cumulative volume of rainfall and discharge
700
Rainfall volume (cf)
600
500
400
300
200
100
Rainfall
Discharge
12:00
13:00
14:00
15:00
16:00
17:00
18:00
19:00
20:00
21:00
22:00
23:00
0:00
1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
9:00
10:00
0
Figure 22: Outdoor test on concrete surface (5-minute interval), Oct. 13, 2009
 Date: 10/21~22/2009
 Max. rainfall intensity: 2.52 in/hr
 Peak discharge: 0.035 cfs
Rainfall intensity and discharge flow rate
0.12
0.040
Rainfall
0.035
Discharge
0.08
0.030
0.025
0.06
0.020
0.015
0.04
0.010
0.02
Discharge rate (cfs)
Precipitation (in)
0.10
0.005
0.000
18:50
19:50
20:50
21:50
22:50
23:50
0:50
1:50
2:50
3:50
4:50
5:50
6:50
7:50
8:50
9:50
10:50
11:50
12:50
13:50
0.00
Cumulative volume of rainfall and discharge
700
Rainfall volume (cf)
600
500
400
300
200
Rainfall
100
Discharge
5:50
6:50
7:50
8:50
9:50
10:50
11:50
12:50
13:50
18:50
19:50
20:50
21:50
22:50
23:50
0:50
1:50
2:50
3:50
4:50
0
Figure 23: Outdoor test on concrete surface (5-minute interval), Oct. 21~22, 2009
 Date: 10/26/2009
 Max. rainfall intensity: 0.84 in/hr
 Peak discharge: 0.014 cfs
Rainfall intensity and discharge flow rate
0.014
Rainfall
Discharge
0.012
0.010
0.020
0.008
0.015
0.006
0.010
0.004
0.005
0.002
0.000
0.000
11:05
11:35
12:05
12:35
13:05
13:35
14:05
14:35
15:05
15:35
16:05
16:35
17:05
17:35
18:05
18:35
19:05
19:35
20:05
20:35
21:05
21:35
22:05
22:35
23:05
23:35
Precipitation (in)
0.025
Discharge rate (cfs)
0.030
Cumulative volume of rainfall and discharge
140
Discharge volume (cf)
Rainfall volume (cf)
120
100
80
60
40
20
Rainfall
Discharge
11:05
11:35
12:05
12:35
13:05
13:35
14:05
14:35
15:05
15:35
16:05
16:35
17:05
17:35
18:05
18:35
19:05
19:35
20:05
20:35
21:05
21:35
22:05
22:35
23:05
23:35
0
Figure 24: Outdoor test on concrete surface (5-minute interval), Oct. 26, 2009
 Date: 11/20~22/2009
 Max. rainfall intensity: 0.84 in/hr
 Peak discharge: 0.015 cfs
Rainfall intensity and discharge flow rate
0.016
0.040
Rainfall
0.035
Discharge
0.030
0.012
0.010
0.025
0.008
0.020
0.006
0.015
0.010
0.004
0.005
0.002
0.000
0.000
Discharge rate (cfs)
0.014
7:40
8:40
9:40
10:40
11:40
12:40
13:40
14:40
15:40
16:40
17:40
18:40
19:40
20:40
21:40
22:40
23:40
0:40
1:40
2:40
3:40
4:40
5:40
6:40
7:40
8:40
9:40
10:40
11:40
12:40
13:40
14:40
15:40
16:40
17:40
Precipitation (in)
0.045
Cumulative volume of rainfall and discharge
400
Rainfall volume (cf)
350
300
250
200
150
100
50
Rainfall
Discharge
7:40
8:40
9:40
10:40
11:40
12:40
13:40
14:40
15:40
16:40
17:40
18:40
19:40
20:40
21:40
22:40
23:40
0:40
1:40
2:40
3:40
4:40
5:40
6:40
7:40
8:40
9:40
10:40
11:40
12:40
13:40
14:40
15:40
16:40
17:40
0
Figure 25: Outdoor test on concrete surface (5-minute interval), Nov. 20~22, 2009
 Date: 12/1~2/2009
 Max. rainfall intensity: 0.084 in/hr
 Peak discharge: 0.024 cfs
Rainfall intensity and discharge flow rate
0.025
0.040
Rainfall
0.035
Discharge
0.020
0.030
0.015
0.025
0.020
0.010
0.015
0.010
Discharge rate (cfs)
Precipitation (in)
0.045
0.005
0.005
0.000
13:20
14:20
15:20
16:20
17:20
18:20
19:20
20:20
21:20
22:20
23:20
0:20
1:20
2:20
3:20
4:20
5:20
6:20
7:20
8:20
9:20
10:20
11:20
0.000
Cumulative volume of rainfall and discharge
600
Rainfall volume (cf)
500
400
300
200
100
Rainfall
Discharge
13:20
14:20
15:20
16:20
17:20
18:20
19:20
20:20
21:20
22:20
23:20
0:20
1:20
2:20
3:20
4:20
5:20
6:20
7:20
8:20
9:20
10:20
11:20
0
Figure 26: Outdoor test on concrete surface (5-minute interval), Dec. 2, 2009
 Date: 12/6/2009
 Max. rainfall intensity: 0.84 in/hr
 Peak discharge: 0.003 cfs
Rainfall intensity and discharge flow rate
0.016
0.004
Rainfall
0.003
Discharge
0.012
0.003
0.010
0.002
0.008
0.002
0.006
0.001
0.004
0.001
0.000
0.000
10:45
12:45
14:45
16:45
18:45
20:45
22:45
0:45
2:45
4:45
6:45
8:45
10:45
12:45
14:45
16:45
18:45
20:45
22:45
0.002
Discharge rate (cfs)
Precipitation (in)
0.014
Cumulative volume of rainfall and discharge
140
Rainfall volume (cf)
120
100
80
60
40
Rainfall
20
Discharge
22:45
20:45
18:45
16:45
14:45
12:45
8:45
10:45
6:45
4:45
2:45
0:45
22:45
20:45
18:45
16:45
14:45
12:45
10:45
0
Figure 27: Outdoor test on concrete surface (5-minute interval), Dec. 6, 2009
Outdoor tests on grass surface
 Date: 9/23~24/2009
 Max. rainfall intensity: 0.84 in/hr
 Peak discharge: 0.000 cfs
Rainfall intensity and discharge flow rate
0.00009
Precipitation (in)
0.025
Rainfall
0.00008
Discharge
0.00007
0.020
0.00006
0.00005
0.015
0.00004
0.010
0.00003
0.00002
0.005
Discharge rate (cfs)
0.030
0.00001
0.00000
19:30
20:30
21:30
22:30
23:30
0:30
1:30
2:30
3:30
4:30
5:30
6:30
7:30
8:30
9:30
10:30
0.000
Cumulative volume of rainfall and discharge
Cumulative volume (cf)
120
100
80
60
40
Rainfall
20
Discharge
10:30
9:30
8:30
7:30
6:30
5:30
4:30
3:30
2:30
1:30
0:30
23:30
22:30
21:30
20:30
19:30
0
Figure 28: Outdoor test on grass surface (5-minute interval), Sept. 23~24, 2009
 Date: 9/24/2009
 Max. rainfall intensity: 0.84 in/hr
 Peak discharge: 0.000 cfs
Rainfall intensity and discharge flow rate
0.0001
0.040
Rainfall
0.035
Discharge
0.0001
0.030
0.0001
0.025
0.0001
0.020
0.015
0.0000
0.010
Discharge rate (cfs)
Precipitation (in)
0.045
0.0000
0.005
23:40
23:10
22:40
22:10
21:40
21:10
20:40
20:10
19:40
19:10
18:40
0.0000
18:10
0.000
Cumulative volume of rainfall and discharge
Cumulative volume (cf)
120
100
80
60
40
Rainfall
20
Discharge
23:40
23:10
22:40
22:10
21:40
21:10
20:40
20:10
19:40
19:10
18:40
18:10
0
Figure 29: Outdoor test on grass surface (5-minute interval), Sept. 24, 2009
 Date: 10/26/2009
 Max. rainfall intensity: 0.84 in/hr
 Peak discharge: 0.001 cfs
Rainfall intensity and discharge flow rate
0.00009
Precipitation (in)
0.025
Rainfall
0.00008
Discharge
0.00007
0.020
0.00006
0.00005
0.015
0.00004
0.010
0.00003
0.00002
0.005
Discharge rate (cfs)
0.030
0.00001
0.00000
17:30
18:30
19:30
20:30
21:30
22:30
23:30
0:30
1:30
2:30
3:30
4:30
5:30
6:30
7:30
8:30
0.000
Cumulative volume of rainfall and discharge
Cumulative volume (cf)
120
100
80
60
40
Rainfall
20
Discharge
8:30
7:30
6:30
5:30
4:30
3:30
2:30
1:30
0:30
23:30
22:30
21:30
20:30
19:30
18:30
17:30
0
Figure 30: Outdoor test on grass surface (5-minute interval), Oct. 26, 2009
 Date: 11/20~21/2009
 Max. rainfall intensity: 0.84 in/hr
 Peak discharge: 0.001 cfs
Rainfall intensity and discharge flow rate
0.016
0.0016
Rainfall
0.012
0.0012
0.010
0.0010
0.008
0.0008
0.006
0.0006
0.004
0.0004
0.002
0.0002
0.000
0.0000
Discharge rate (cfs)
0.0014
Discharge
3:50
5:50
7:50
9:50
11:50
13:50
15:50
17:50
19:50
21:50
23:50
1:50
3:50
5:50
7:50
9:50
11:50
13:50
Precipitation (in)
0.014
Cumulative volume of rainfall and discharge
Cumulative volume (cf)
350
300
250
200
Rainfall
150
Discharge
100
50
13:50
11:50
9:50
7:50
5:50
3:50
1:50
23:50
21:50
19:50
17:50
15:50
13:50
11:50
9:50
7:50
5:50
3:50
0
Figure 31: Outdoor test on grass surface (5-minute interval), Nov. 20~21, 2009
 Date: 12/1~2/2009
 Max. rainfall intensity: .84 in/hr
 Peak discharge: 0.009 cfs
Rainfall intensity and discharge flow rate
0.0090
Precipitation (in)
0.05
Rainfall
0.0080
Discharge
0.0070
0.04
0.0060
0.0050
0.03
0.0040
0.02
0.0030
0.0020
0.01
Discharge rate (cfs)
0.06
0.0010
11:30
9:30
7:30
5:30
3:30
1:30
23:30
21:30
19:30
17:30
15:30
0.0000
13:30
0.00
Cumulative volume of rainfall and discharge
Cumulative volume (cf)
600
500
400
300
Rainfall
Discharge
200
100
11:30
9:30
7:30
5:30
3:30
1:30
23:30
21:30
19:30
17:30
15:30
13:30
0
Figure 32: Outdoor test on grass surface (5-minute interval), Dec. 1~2, 2009
 Date: 12/6~7/2009
 Max. rainfall intensity: 0.84 in/hr
 Peak discharge: 0.001 cfs
Rainfall intensity and discharge flow rate
0.016
0.0006
Rainfall
0.0005
Discharge
0.012
0.0004
0.010
0.008
0.0003
0.006
0.0002
0.004
Discharge rate (cfs)
Precipitation (in)
0.014
0.0001
0.002
14:00
16:00
12:00
10:00
6:00
8:00
4:00
2:00
22:00
0:00
20:00
16:00
18:00
14:00
12:00
0.0000
10:00
0.000
Cumulative volume of rainfall and discharge
Cumulative volume (cf)
120
100
80
60
Rainfall
Discharge
40
20
16:00
14:00
12:00
10:00
8:00
6:00
4:00
2:00
0:00
22:00
20:00
18:00
16:00
14:00
12:00
10:00
0
Figure 33: Outdoor test on grass surface (5-minute interval), Dec. 6~7, 2009