Table 2. Characteristics of rainstorms that triggered lahars on the east side of Mount Pinatubo (rain gages PI2Z, MSAC, FNGZ, and QADZ) for period July 18 -October 31, 1991.
["Storms" defined as periods of rainfall separated by more than 6 h with no rain. "Major" lahars defined as having durations greater than 2 h with moderate to high acoustic amplitude. "Minor" lahars have either durations less than 2 h or low acoustic amplitudes. Acoustic flow sensors: ABAC, Abacan; GUMA, Gumain; LSAC, lower Sacobia. -, no data or activity.]
|
Rain gage |
Date |
Storm duration |
Total rainfall (mm) |
Average intensity |
Maximum intensity |
Lahar activity |
|---|---|---|---|---|---|---|
|
PI2Z |
7/18/91 |
4.7 |
39.1 |
8.4 |
29.6 (1 h) |
Major - LSAC |
|
QADZ |
|
- |
0 |
- |
- |
|
|
PI2Z |
7/19 |
12.8 |
26.0 |
2.1 |
9.3 (1 h) |
Minor - LSAC |
|
QADZ |
|
- |
0 |
- |
- |
|
|
PI2Z |
7/22 |
5.7 |
121.0 |
21.4 |
57.3 (1.5 h) |
Major - LSAC |
|
PI2Z |
7/23 |
19.6 |
53.1 |
2.7 |
6.6 (4.7 h) |
Minor - LSAC |
|
PI2Z |
7/24 |
- |
0 |
- |
- |
Major - ABAC |
|
PI2Z |
7/25 |
1.4 |
7.1 |
5.0 |
5.0 (1.4 h) |
Minor - LSAC |
|
|
(Storm 1) |
|
|
|
|
Major - ABAC |
|
PI2Z |
7/25 |
6.0 |
12.0 |
2.1 |
4.9 (0.8 h) |
Major - ABAC |
|
|
(Storm 2) |
|
|
|
|
Minor - LSAC |
|
PI2Z |
7/26 |
16.0 |
45.0 |
2.8 |
- |
Major - LSAC |
|
|
|
|
|
|
|
Minor - ABAC |
|
PI2Z |
7/31 |
- |
0 |
- |
- |
Major - LSAC |
|
FNGZ |
|
- |
0 |
- |
- |
Major - ABAC |
|
QADZ |
|
6.7 |
26.9 |
4.1 |
76.1 (0.3 h) |
|
|
PI2Z |
8/1 |
4.0 |
23.9 |
6.0 |
14.8 (0.3 h) |
Major - LSAC |
|
FNGZ |
|
2.8 |
19.1 |
6.8 |
12.0 (0.5 h) |
Minor - ABAC |
|
QADZ |
|
5.4 |
29.0 |
5.4 |
90.1 (0.1 h) |
|
|
PI2Z |
8/5 |
4.5 |
56.1 |
12.4 |
12.4 (4.5 h) |
Major - LSAC |
|
|
|
|
|
|
|
Major - ABAC |
|
PI2Z |
8/8 |
.4 |
7.1 |
16.7 |
16.7 (0.4 h) |
Minor - ABAC |
|
QADZ |
|
2.2 |
3.0 |
1.3 |
1.3 (2.2 h) |
Minor - GUMA |
|
FNGZ |
|
- |
0 |
- |
- |
|
|
PI2Z |
8/10 |
3.0 |
12.0 |
3.9 |
3.9 (3.0 h) |
Minor - ABAC |
|
FNGZ |
|
- |
0 |
- |
- |
Minor - GUMA |
|
QADZ |
|
1.9 |
12.0 |
6.5 |
6.5 (1.9 h) |
|
|
PI2Z |
8/11 |
2.2 |
25.0 |
11.7 |
33.4 (0.3 h) |
Major - LSAC |
|
FNGZ |
|
2.2 |
83.0 |
37.8 |
82.5 (0.1 h) |
Minor - ABAC |
|
QADZ |
|
1.9 |
32.0 |
17.3 |
125.1 (0.1 h) |
Minor - GUMA |
|
P12Z |
8/13 |
4.0 |
10.1 |
2.5 |
- |
Major - LSAC |
|
FNGZ |
|
- |
0 |
- |
- |
Major - ABAC |
|
QADZ |
|
4.8 |
38.0 |
7.9 |
9.1 (0.9 h) |
Minor - GUMA |
|
PI2Z |
8/14 |
4.0 |
19.1 |
4.7 |
4.7 (4.0 h) |
Major - LSAC |
|
FNGZ |
(Storm 1) |
- |
0 |
- |
- |
Major - ABAC |
|
QADZ |
|
4.8 |
51.0 |
10.6 |
24.1 (0.8 h) |
Minor - GUMA |
|
Rain gage |
Date |
Storm duration |
Total rainfall (mm) |
Average intensity |
Maximum intensity |
Lahar activity |
|---|---|---|---|---|---|---|
|
PI2Z |
8/14 |
4.0 |
25.0 |
6.3 |
58.9 (0.2 h) |
Major - LSAC |
|
FNGZ |
(Storm 2) |
2.8 |
7.1 |
2.5 |
2.5 (2.8 h) |
Major - ABAC |
|
QADZ |
|
3.0 |
32.0 |
10.9 |
36.4 (0.2 h) |
Minor - GUMA |
|
PI2Z |
8/15-16 |
13.8 |
34.8 |
2.5 |
- |
Major - LSAC |
|
FNGZ |
|
13.0 |
29.0 |
2.2 |
6.0 (1.0 h) |
Minor - ABAC |
|
QADZ |
|
17.8 |
68.0 |
3.8 |
18.3 (0.2 h |
Minor - GUMA |
|
PI2Z |
8/16 |
14.0 |
39.2 |
2.8 |
- |
Major - LSAC |
|
FNGZ |
(Storm 2) |
13.5 |
76.1 |
5.7 |
18.0 (0.5 h) |
Minor - ABAC |
|
QADZ |
|
4.8 |
36.1 |
7.4 |
10.2 (0.1 h) |
Minor - GUMA |
|
PI2Z |
8/17 |
11.9 |
12.0 |
.9 |
- |
Major - LSAC |
|
FNGZ |
|
10.5 |
12.0 |
1.1 |
- |
|
|
QADZ |
|
14.5 |
34.0 |
2.4 |
3.8 (0.1 h) |
|
|
PI2Z |
8/18 |
21.4 |
19.1 |
.9 |
- |
Major - LSAC |
|
FNGZ |
|
23.0 |
39.1 |
1.7 |
6.0 (0.5 h) |
Minor - ABAC |
|
QADZ |
|
25.9 |
116.1 |
4.4 |
7.2 (1.4 h) |
|
|
PI2Z |
8/19-21 |
40.5 |
142.1 |
3.5 |
21.4 (0.3 h) |
Major - LSAC |
|
FNGZ |
|
45.6 |
551.1 |
12.1 |
119.7 (0.2 h) |
Major - ABAC |
|
QADZ |
|
59.9 |
485.1 |
8.0 |
60.0 (0.5 h) |
Major - GUMA |
|
PI2Z |
8/21 |
- |
0 |
- |
- |
Major - LSAC |
|
FNGZ |
(Storm 2) |
2.0 |
12.0 |
6.0 |
8.3 (0.5 h) |
Minor - ABAC |
|
QADZ |
|
1.8 |
18.0 |
10.2 |
21.4 (0.4 h) |
|
|
PI2Z |
8/22 |
- |
0 |
- |
- |
Major - LSAC |
|
FNGZ |
|
- |
0 |
- |
- |
Minor - ABAC |
|
QADZ |
|
4.6 |
23.9 |
4.9 |
60.0 (1.0 h) |
Major - GUMA |
|
PI2Z |
8/23 |
- |
0 |
- |
- |
Major - LSAC |
|
FNGZ |
|
- |
0 |
- |
- |
Minor - ABAC |
|
QADZ |
|
9.6 |
47.1 |
4.9 |
21.3 (05 h) |
Minor - GUMA |
|
P12Z |
8/24 |
10.0 |
58.0 |
5.8 |
20.0 (0.1 h) |
Major - LSAC |
|
FNGZ |
|
7.0 |
32.0 |
4.6 |
23.6 (0.4 h) |
Major - ABAC |
|
QADZ |
|
4.4 |
50.1 |
11.3 |
77.0 (0.1 h) |
|
|
P12Z |
8/25 |
5.0 |
72.0 |
14.5 |
58.3 (0.1 h) |
Major - LSAC |
|
FNGZ |
|
- |
0 |
- |
- |
Major - ABAC |
|
QADZ |
|
9.1 |
199.1 |
21.7 |
58.9 (0.2 h) |
Major - GUMA |
|
PI2Z |
8/26 |
1.0 |
2.0 |
2.0 |
2.0 (1.0 h) |
Minor - LSAC |
|
FNGZ |
|
- |
0 |
- |
- |
Major - ABAC |
|
QADZ |
|
6.3 |
18.0 |
2.8 |
2.8 (6.3 h) |
|
|
PI2Z |
8/27 |
- |
0 |
- |
- |
Major - LSAC |
|
FNGZ |
|
- |
0 |
- |
- |
Major - ABAC |
|
QADZ |
|
.7 |
17.0 |
25.4 |
25.4 (0.7 h) |
|
|
Rain gage |
Date |
Storm duration |
Total rainfall (mm) |
Average intensity |
Maximum intensity |
Lahar activity |
|---|---|---|---|---|---|---|
|
PI2Z |
8/28 |
1.0 |
3.9 |
3.9 |
3.9 (1.0 h) |
Minor - LSAC |
|
FNGZ |
|
- |
0 |
- |
- |
Major - ABAC |
|
QADZ |
|
- |
0 |
- |
- |
|
|
PI2Z |
8/29 |
2.9 |
6.0 |
2.0 |
7.4 (0.3 h) |
Major - LSAC |
|
FNGZ |
|
- |
0 |
- |
- |
Major - ABAC |
|
QADZ |
|
3.3 |
33.1 |
10.1 |
13.9 (0.6 h) |
|
|
PI2Z |
8/30 |
7.0 |
28.0 |
3.9 |
14.8 (0.3 h) |
Minor - LSAC |
|
FNGZ |
|
- |
0 |
- |
- |
Major - ABAC |
|
QADZ |
|
6.5 |
40.0 |
6.1 |
17.3 (0.6 h) |
Minor - GUMA |
|
PI2Z |
8/31 |
1.0 |
10.1 |
10.1 |
10.1 (1.0 h) |
Major - LSAC |
|
FNGZ |
|
- |
0 |
- |
- |
|
|
QADZ |
|
4.0 |
20.0 |
5.0 |
12.4 (0.1 h) |
|
|
PI2Z |
9/1 |
3.4 |
57.2 |
17.0 |
55.3 (0.3 h) |
Major - LSAC |
|
QADZ |
|
9.8 |
117.7 |
12.0 |
141.8 (0.1 h) |
Major - ABAC |
|
|
|
|
|
|
|
Major - GUMA |
|
PI2Z |
9/2 |
- |
0 |
- |
- |
Minor - LSAC |
|
FNGZ |
|
- |
0 |
- |
- |
Minor - ABAC |
|
QADZ |
|
4.8 |
27.1 |
5.7 |
15.0 (0.6 h) |
Minor - GUMA |
|
PI2Z |
9/3 |
3.0 |
17.0 |
5.7 |
14.0 (0.5 h) |
Major - LSAC |
|
FNGZ |
|
1.5 |
6.0 |
3.9 |
3.9 (1.5 h) |
Major - ABAC |
|
QADZ |
|
3.8 |
40.0 |
10.6 |
38.9 (0.2 h) |
|
|
PI2Z |
9/4 |
5.3 |
26.0 |
4.9 |
26.1 (0.2 h) |
Major - LSAC |
|
FNGZ |
|
5.0 |
13.1 |
2.7 |
3.0 (3.0 h) |
Major - ABAC |
|
QADZ |
|
4.4 |
71.0 |
16.1 |
16.1 (4.4 h) |
Major - GUMA |
|
PI2Z |
9/6-8 |
22.8 |
94.3 |
4.1 |
21.6 (0.6 h) |
Major - LSAC |
|
FNGZ |
|
11.4 |
21.3 |
1.9 |
6.5 (1.0 h) |
Major - ABAC |
|
QADZ |
|
60.7 |
183.6 |
3.0 |
26.8 (0.8 h) |
Minor - GUMA |
|
P12Z |
9/10 |
6.0 |
75.6 |
12.6 |
29.6 (1.4 h) |
Minor - LSAC |
|
FNGZ |
|
2.0 |
5.7 |
2.8 |
6.0 (0.9 h) |
Major - ABAC |
|
QADZ |
|
7.5 |
43.9 |
5.8 |
50.1 (0.4 h) |
Minor - GUMA |
|
PI2Z |
9/12 |
- |
0 |
- |
- |
Minor - ABAC |
|
FNGZ |
|
1.0 |
8.2 |
8.2 |
8.2 (1.0 h) |
|
|
QADZ |
|
2.8 |
3.2 |
1.1 |
- |
|
|
PI2Z |
9/13 |
- |
0 |
- |
- |
Major - LSAC |
|
FNGZ |
|
3.5 |
9.6 |
2.7 |
11.7 (0.4 h) |
Major - ABAC |
|
QADZ |
|
29.0 |
37.6 |
1.3 |
35.1 (0.4 h) |
|
|
Rain gage |
Date |
Storm duration |
Total rainfall (mm) |
Average intensity |
Maximum intensity |
Lahar activity |
|---|---|---|---|---|---|---|
|
PI2Z |
9/14 |
6.9 |
27.2 |
3.9 |
- |
Minor - LSAC |
|
FNGZ |
|
2.0 |
8.8 |
4.4 |
- |
Minor - ABAC |
|
QADZ |
|
9.2 |
60.0 |
6.6 |
50.2 (0.8 h) |
|
|
MSAC |
|
3.8 |
15.3 |
4.1 |
- |
|
|
PI2Z |
9/15-20 |
75.3 |
138.0 |
1.9 |
30.4 (0.8 h) |
Minor - LSAC |
|
FNGZ |
|
102.5 |
63.9 |
.6 |
- |
Major - ABAC |
|
QADZ |
|
117.6 |
483.2 |
4.1 |
20.8 (4.4 h) |
Minor - GUMA |
|
MSAC |
|
66.3 |
190.1 |
2.8 |
32.6 (0.6 h) |
|
|
PI2Z |
9/22-23 |
17.6 |
23.9 |
1.4 |
25.5 (0.4 h) |
Minor - ABAC |
|
FNGZ |
|
3.6 |
3.9 |
1.1 |
- |
|
|
QADZ |
|
20.4 |
18.4 |
0.9 |
5.5 (0.8 h) |
|
|
PI2Z |
9/27- |
26.7 |
37.6 |
1.4 |
- |
Minor - ABAC |
|
FNGZ |
10/1 |
12.8 |
10.1 |
.8 |
- |
|
|
QADZ |
|
103.8 |
314.1 |
3.0 |
25.2 (1.2 h) |
|
|
PI2Z |
10/3 |
1.9 |
58.7 |
30.9 |
157.2 (0.1 h) |
Minor - ABAC |
|
FNGZ |
|
1.6 |
6.0 |
3.8 |
- |
|
|
QADZ |
|
6.2 |
18.7 |
3.0 |
30.6 (0.5 h) |
|
|
PI2Z |
10/4-5 |
.7 |
28.8 |
40.6 |
40.6 (0.7 h) |
Minor - LSAC |
|
FNGZ |
|
36.2 |
17.2 |
.5 |
6.3 (1.7 h) |
Major - ABAC |
|
QADZ |
|
6.5 |
15.3 |
2.4 |
9.5 (0.5 h) |
|
|
PI2Z |
10/13 |
- |
- |
- |
- |
Major - ABAC |
|
FNGZ |
|
4.3 |
10.9 |
2.5 |
- |
|
|
QADZ |
|
6.3 |
53.9 |
8.5 |
50.4 (0.2 h) |
|
|
MSAC |
|
3.6 |
56.4 |
15.9 |
29.5 (1.1 h) |
|
|
PI2Z |
10/14 |
.6 |
5.2 |
8.2 |
- |
Minor - LSAC |
|
FNGZ |
|
- |
- |
- |
- |
Minor - ABAC |
|
QADZ |
|
9.7 |
38.0 |
3.9 |
17.8 (0.5 h) |
|
|
MSAC |
|
.8 |
21.3 |
25.5 |
48.0 (0.3 h) |
|
|
PI2Z |
10/15 |
1.6 |
10.9 |
6.8 |
12.4 (0.6 h) |
Minor - ABAC |
|
FNGZ |
|
- |
- |
- |
- |
|
|
QADZ |
|
- |
- |
- |
- |
|
|
MSAC |
|
- |
0 |
- |
- |
|
|
PI2Z |
10/16 |
- |
- |
- |
- |
Major - ABAC |
|
FNGZ |
|
- |
- |
- |
- |
|
|
QADZ |
|
9.5 |
8.7 |
.9 |
.9 (9.5 h) |
|
|
MSAC |
|
7.1 |
55.6 |
7.9 |
37.3 (0.8 h) |
|
|
PI2Z |
10/28 |
30.3 |
78.8 |
2.7 |
- |
Minor - LSAC |
|
FNGZ |
|
14.0 |
13.5 |
.9 |
- |
Major - ABAC |
|
QADZ |
|
36.5 |
221.6 |
6.1 |
21.4 (1.2 h) |
|
|
MSAC |
|
12.4 |
66.5 |
5.4 |
27.4 (0.5 h) |
|