V.2. Hubungan Debit Banjir Dengan Durasi Banjir
Lamanya banjir dapat diperkirakan dengan cara menganalisa debit menggunakan metode hidrograf satuan, sehingga dapat diperkirakan besarnya debit
yang terjadi dan durasi banjir dalam jam-jaman. Pada penelitian ini perhitungan dilakukan dengan hidrograf satuan sintetik HSS Nakayasu.
Tabel 5.7. Hubungan Banjir Dengan Durasi Limpasan
Akibat Hujan mm
T jam Qt
m
3
dtkmm Qt
terkoreksi 33,65
1 jam 6,23
2 jam 3,18
3 jam 1,25
4 jam 1,82
5 jam total
0,000 0,000
0,000 0,000
0,000 0,000
0,000 0,000
1 0,082
0,102 3,419
0,632 0,323
0,127 0,185
4,686
2 0,432
0,536 18,044
3,338 1,707
0,670 0,976
24,735
3 1,142
1,419 47,748
8,833 4,517
1,774 2,582
65,454
4 2,277
2,830 95,237
17,618 9,010
3,538 5,151
130,553
5 3,891
4,835 162,701
30,098 15,392
6,044 8,800
223,035
6 6,027
7,489 252,014
46,621 23,841
9,362 13,630
345,468
7 8,725
10,842 364,836
67,492 34,514
13,553 19,733
500,126
8 12,021
14,938 502,664
92,989 47,553
18,673 27,187
689,065
9 15,948
19,818 666,874
123,367 63,087
24,772 36,069
914,169
Universitas Sumatera Utara
9,9 20,046
24,912 838,275
155,075 79,302
31,139 45,339 1149,129
10 19,863
24,684 830,623
153,659 78,578
30,855 44,925 1138,640
11 18,242
22,669 762,825
141,117 72,164
28,337 41,258 1045,702
12 16,753
20,819 700,562
129,599 66,274
26,024 37,891
960,349
13 15,386
19,120 643,380
119,021 60,865
23,900 34,798
881,963
14 14,130
17,559 590,866
109,306 55,897
21,949 31,958
809,975
15 12,977
16,126 542,638
100,384 51,334
20,157 29,349
743,863
16 11,917
14,810 498,347
92,190 47,144
18,512 26,954
683,147
17 10,945
13,601 457,671
84,666 43,296
17,001 24,754
627,387
18 10,051
12,491 420,314
77,755 39,762
15,613 22,733
576,178
19 9,231
11,471 386,007
71,408 36,517
14,339 20,878
529,149
20 8,478
10,535 354,501
65,580 33,536
13,169 19,174
485,959
21 7,786
9,675 325,565
60,227 30,799
12,094 17,609
446,294
22 7,150
8,885 298,992
55,311 28,285
11,107 16,171
409,866
23 6,566
8,160 274,588
50,797 25,976
10,200 14,851
376,412
24 6,031
7,494 252,175
46,651 23,856
9,368 13,639
345,688
25 5,692
7,073 238,002
44,029 22,515
8,841 12,873
326,260
26 5,377
6,683 224,869
41,599 21,273
8,353 12,162
308,256
27 5,081
6,314 212,460
39,303 20,099
7,892 11,491
291,245
28 4,800
5,965 200,735
37,135 18,990
7,457 10,857
275,173
29 4,535
5,636 189,658
35,085 17,942
7,045 10,258
259,988
30 4,285
5,325 179,192
33,149 16,952
6,656 9,692
245,641
31 4,049
5,031 169,304
31,320 16,016
6,289 9,157
232,086
32 3,825
4,754 159,961
29,592 15,133
5,942 8,652
219,279
33 3,614
4,491 151,134
27,959 14,297
5,614 8,174
207,178
34 3,415
4,243 142,794
26,416 13,508
5,304 7,723
195,745
Universitas Sumatera Utara
35 3,226
4,009 134,914
24,958 12,763
5,012 7,297
184,944
36 3,048
3,788 127,469
23,581 12,059
4,735 6,894
174,738
37 2,880
3,579 120,435
22,280 11,393
4,474 6,514
165,095
38 2,721
3,382 113,789
21,050 10,765
4,227 6,154
155,985
39 2,571
3,195 107,509
19,888 10,171
3,994 5,815
147,377
40 2,429
3,019 101,577
18,791 9,609
3,773 5,494
139,244
41 2,295
2,852 95,971
17,754 9,079
3,565 5,191
131,560
42 2,168
2,695 90,675
16,774 8,578
3,368 4,904
124,300
43 2,049
2,546 85,672
15,849 8,105
3,182 4,634
117,441
44 1,936
2,405 80,944
14,974 7,657
3,007 4,378
110,960
45 1,829
2,273 76,477
14,148 7,235
2,841 4,136
104,837
46 1,746
2,170 73,032
13,510 6,909
2,713 3,950
100,114
47 1,674
2,080 69,988
12,947 6,621
2,600 3,785
95,942
48 1,604
1,993 67,071
12,408 6,345
2,491 3,628
91,943
49 1,537
1,910 64,276
11,891 6,081
2,388 3,476
88,111
50 1,473
1,831 61,597
11,395 5,827
2,288 3,332
84,438
51 1,412
1,754 59,029
10,920 5,584
2,193 3,193
80,919
52 1,353
1,681 56,569
10,465 5,351
2,101 3,060
77,546
53 1,296
1,611 54,211
10,029 5,128
2,014 2,932
74,314
54 1,242
1,544 51,952
9,611 4,915
1,930 2,810
71,217
55 1,191
1,480 49,786
9,210 4,710
1,849 2,693
68,248
56 1,141
1,418 47,711
8,826 4,514
1,772 2,581
65,404
57 1,093
1,359 45,723
8,458 4,325
1,698 2,473
62,678
58 1,048
1,302 43,817
8,106 4,145
1,628 2,370
60,065
59 1,004
1,248 41,991
7,768 3,972
1,560 2,271
57,562
60 0,962
1,196 40,240
7,444 3,807
1,495 2,176
55,163
Universitas Sumatera Utara
Hubungan Durasi Hujan dan Debit Banjir
200 400
600 800
1000 1200
1400
5 10
15 20
25 30
35 40
45 50
55 60
65
Durasi jam D
e b
it m
3 d
e ti
k
Akibat hujan 33,65 mm Akibat hujan 6,22 mm
Akibat hujan 3,18 mm Akibat hujan 1,82 mm
Akibat hujan 1,25 mm Total
Gambar 5.5. Grafik Durasi Banjir Dengan Debit Banjir Metode HSS Nakayasu
Dari tabel 5.7. dan gambar 5.5. didapat bahwa puncak banjir terjadi pada durasi 9,9 jam dimana hujan yang turun adalah akibat hujan maksimum jam-jaman yang didapat dari
BMKG Sampali.
Universitas Sumatera Utara
V.3. Perencanaan Tinggi Tanggul
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