Studi sensitivitas penduduk terhadap bahaya awan panas Gunungapi Merapi di kawasan rawan bencana II dan III

YUSUP, Yasin, Prof.Dr. Sutikno

2006 | Tesis | S2 Geografi

Studi sensitivitas penduduk terhadap bahaya awan panas di kawasan rawan bencana II dan III Gunungapi Merapi, dilatarbelakangi fenomena bergemingnya penduduk di sektor lereng Barat Laut (warga dusun Stabelan) dan penambang pasir di hulu Kali Blongkeng dan Putih (“Srumbung”) saat status aktivitas G. Merapi tahun 2001 sudah siaga. Mereka melakukan aktivitas sebagaimana biasanya, padahal daerah tersebut merupakan daerah paling terbuka terhadap serangan awan panas. Pertanyaannya bagaimana sensitivitas penduduk terhadap bahaya awan panas ? Penelitian ini bertujuan: 1) mengetahui karakteristik erupsi G. Merapi abad 19 dan 20; 2) mengkaji keterbukaan fisik masing-masing sektor lereng terhadap bahaya awan panas; 3) mengetahui kerentanan penduduk di KRB II dan III terhadap bahaya awan panas, dan 4) mengetahui sensitivitas penduduk terhadap bahaya awan panas di KRB II dan III. Metode historis, deskriptif, dan eksplanatif digunakan dalam penelitian ini. Metode historis digunakan untuk mengetahui karakteristik erupsi abad 19 dan 20. Metode deskriptif digunakan untuk mengungkap keterbukaan fisik dan kerentanan penduduk terhadap bahaya awan panas. Metode eksplanatif digunakan untuk menjawab pertanyaan mengapa seolah penduduk tidak sensitif terhadap bahaya awan panas. Analisis data dilakukan dengan uji statistik non parametrik (Binomial, Chi- Square, Mann-Whitney, Kruskal-Wallis, Cochran, dan Somers’d) dan analisis spasial (buffer dan overlay). Penelitian ini menyimpulkan bahwa erupsi semakin sering terjadi pada abad 20 berbanding abad 19 tetapi magnitudnya mengecil. Meskipun magnitud mengecil bencana lebih sering terjadi, naik 2 kali lipatnya. Artinya bukan aspek bahaya yang meningkat, tetapi kerentanan penduduk yang meningkat. Pita toleransi sosialekonomi dan batas kerusakan terhadap bahaya awan panas menyempit, sehingga erupsi kecil (VEI 2) pun sudah menimbulkan bencana yang besar (korban > 50 jiwa). Hal ini terlihat secara nyata dari menurunnya asosiasi antara meningkatnya jumlah korban dengan meningkatnya magnitud erupsi yang semula pada abad 19 sebesar 0,913 menjadi 0,434 pada abad 20. Penduduk semakin berisiko terhadap bencana karena penduduk dalam menyikapi bahaya menggunakan pendekatan kelentingan, sehingga ambang toleransi penduduk terhadap bahaya meningkat, sebaliknya sensitivitas terhadap bahaya menurun. Akibatnya bencana lebih banyak terjadi. Sensitivitas penduduk terhadap bahaya awan panas beragam, terlihat dari batas kerusakan yang berbeda. Batas kerusakan terlebar dimiliki Sektor Barat (12 km), berikutnya Sektor Selatan (5,5 km), dan paling sempit Sektor Utara (3,5 km). Sementara Sektor Timur tertutup terhadap bahaya awan panas pada abad 20. Awan panas 7 km bagi Lereng Barat diterima sebagai sumberdaya, tetapi bila mengarah Utara atau Selatan sudah menimbulkan bencana. Aktivitas erupsi dominan ke Sektor Barat (71,05%) disebabkan adanya kontrol morfologi setting kawah berbentuk tapal kuda terbuka ke arah Barat. Terlepas dari hal tersebut, keterbukaan fisik bersifat dinamis, semua sektor lereng terbuka dengan tingkatan bahaya dan kerentanan yang berbeda. Bencana biasanya terjadi saat pusat aktivitas dan lereng aktif berubah, sementara sensitivitas penduduk terhadap bahaya menurun.

This study of the human sensitivity to glowing cloud hazard in hazard zone (HZ) II and III is based on the fact that the inhabitant in North-West flank sector (the Stabelan village inhabitants) and the sand-miners in Blongkeng river and Putih upstream (Srumbung) did not pay any attention to Merapi Volcano dynamics of 2001 eruption, while the status of volcanic activity goes to ‘alert’. They went on to work as they usually do, whereas the area is the most open area upon the glowing cloud hazard. The question is how is their sensitivity toward the glowing cloud hazard ? This study is aimed to (1) understand the characteristics of Merapi eruption in the 19 and 20 century (2) analyze the physical exposure of each flank sector toward the glowing cloud hazard (3) analyze the inhabitant vulnerability to the glowing cloud hazard in the HZ II and III, and (4) evaluate the inhabitant’ sensitivity to glowing cloud hazard in the HZ II and III. This study is conducted in middle and upper flank, and the peak of Merapi volcano. Historically, these areas have evidently suffered from the glowing cloud. This study uses historical, descriptive as well as explanative approaches. The historical approach is used to analyze the characteristics of the 19 and 20 century eruptions. The descriptive one is used to disclose how the physical exposures and the sensitivity of the inhabitant toward the glowing cloud hazard. The explanative approach is used to answer the question of why are the inhabitant of HZ II and III seemingly insensitive of the glowing cloud hazard. The data will be analyzed by qualitative analysis both including nonparametric statistical (Binominal, Chi-square, Mann-Whitney, Kruskal-Wallis, Cochran, and Sommers’d) and spatial analysis (buffer and overlay). This study shows the fact that there were more eruptions occurred in the 20 century than those did in the 19 century. Although the magnitude became smaller, the disaster more often occurred. This means that the band of social economic tolerance and the damage threshold is narrowing, so that even the small scale eruption (VEI 2) can cause a huge damage (more than 50 deaths). This fact is significantly shown from the decreasing association of the rising of victims and that of eruption’s magnitude; it were 0,913 in the 19 century become 0,434 in the 20 century. Consequently, the inhabitants are more vulnerable to the hazard because they recognize it by recilience approach, so that the tolerance threshold of them toward the hazard is increasing, but their sensitivity toward it decreasing. The result is that the disaster become more frequent. The inhabitant’s sensitivity to glowing cloud hazards is vary; which is reflected in the differences of damage threshold. The broadest damage threshold occurred in the West flank (12 km), and then in the Southern flank (5,5 km), whereas the smallest one occurred in the northern flank (3,5 km). The 7 km glowing cloud is not yet dangerous for the west flank because the residential area beyond the reach of it. The inhabitants instead consider its effect as resources of sand supply. However, if it flows to the other side, to the northern or southern side for example, it will call an extreme and dangerous damage. The eruption activity is dominant to western side (71,05%), and otherwise, the eastern flank is closed to the glowing cloud hazard in the 20 century. This is because of morphological control which is the setting of shoe shaped nested crater openned to west. Regardless of the morphological control reality, the physical exposure is in fact dynamic, all slope sides are opened with different level of hazard and vulnerability. Disaster happens when the central activity and the active slope are changing, when the inhabitant’s sensitivity to it is decreasing.

Kata Kunci : Gunungapi,Bahaya Awan Panas,Sensitivitas Penduduk, Sensitivity, Magnitude of Eruption, Band of Social-Economic Tolerance, Damage Treshold