Longsor Dahsyat Jemblung Banjarnegara

Longsor Dahsyat Jemblung dan Takdir Kebumian Banjarnegara

Senja menjelang tiba di segenap Kabupaten Banjarnegara, propinsi Jawa Tengah, pada Jumat 12 Desember 2014 Tarikh Umum (TU) lalu. Dalam kondisi normal panoramanya bakal memukau siapapun, saat langit berangsur-angsur menjadi memerah tembaga di kala Matahari memerah dan meredup, pemandangan yang selalu menimbulkan kesan spiritual dan relijius. Namun sore itu tak satupun yang dapat disaksikan. Bahkan seberkas sinar Matahari tak juga nampak. Banjarnegara sedang kehujanan. Titik-titik air hujan yang sangat deras meredam segenap kabupaten tersebut sejak sehari sebelumnya. Stasiun geofisika kelas III Banjarnegara yang dioperasikan oleh BMKG (Badan Meteorologi Klimatologi dan Geofisika) mencatat curah hujan sepanjang Kamis 11 Desember 2014 TU mencapai 112,7 milimeter. Dan sehari kemudian curah hujannya masih sebesar 101,8 milimeter. Dalam dua hari saja saja intensitas hujan yang mengguyur seantero Banjarnegara telah sebesar 214,5 milimeter. Di waktu-waktu lalu, pada umumnya curah hujan sebanyak itu membutuhkan waktu sebulan Desember penuh (rata-rata) dalam menjatuhi segenap Banjarnegara. Jelas sudah, dengan volume air hujan yang setara dengan yang rata-rata diguyurkan selama 31 hari penuh, hujan sepanjang 11 hingga 12 Desember 2014 di Banjarnegara berkualifikasi hujan sangat deras atau hujan ekstrim.

Gambar 1. Wajah dusun Jemblung, desa Sampang (Banjarnegara) antara sebelum dan sesudah bencana tanah longsor dahsyat 12 Desember 2014 TU. Citra sebelum bencana diambil dari sisi utara jalan raya Banjarnegara-Dieng menghadap ke barat laut-utara. Nampak masjid al-Iman di latar belakang. Sementara citra sesudah bencana diambil dari lokasi yang lebih tinggi namun tidak seberapa jauh dari lokasi pengambilan citra sebelum bencana, dengan arah pandang yang sama. Nampak semua sudah berubah menjadi timbunan lumpur. Sumber: Nurmansyah, 2014.

Hujan yang sangat deras ini membuat sekujur Banjarnegara menggigil dan berharap-harap cemas. Kabar meluapnya Sungai Serayu, sungai utama di kabupaten ini, sembari mengalirkan arusnya demikian deras pun menyebar kemana-mana. Sedemikian berlimpah air sungai ini sehingga tinggi genangan di Waduk Panglima Besar Sudirman (Mrica), yang ada di aliran sungai Serayu, pun mencapai maksimum dalam waktu singkat. Akibatnya pengelola dipaksa membuka pintu-pintu pelimpas air (spillway)-nya untuk tetap menjaga keamanan bendung. Air Serayu pun menderas ke hilir dan sempat menenggelamkan sejumlah rumah. Kabar tak berkeruncingan pun menyebar kemana-mana, mewartakan waduk telah bobol dan menenggelamkan hilir sungai meski hal ini segera dibantah oleh pengelola bendungan. Titik-titik tanah longsor pun bermunculan dimana-mana di kabupaten ini. Namun yang terburuk belumlah tiba.

Pada Jumat senja itu mayoritas penduduk dusun Jemblung, desa Sampang, kecamatan Karangkobar lebih memilih meriung di kediamannya masing-masing. Hujan sangat deras hari itu baru saja berlalu. Namun titik-titik air yang lebih lembut masih berjatuhan, membuat orang-orang enggan keluar. Dusun sederhana berhawa sejuk itu terletak pada elevasi 930 hingga 940 meter dpl (dari paras air laut rata-rata). Mayoritas penduduk bergelut di dunia pertanian. Dusun ini nyaris tak dikenal orang luar Karangkobar, meski berada di jalur jalan raya utama yang menghubungkan kota Banjarnegara dengan Leksana (ibukota kecamatan Karangkobar) dan Dataran Tinggi Dieng. Jalan raya yang sama juga menjadi salah satu poros penghubung Banjarnegara dengan Pekalongan di utara. Jalan tersebut telah beraspal mulus dengan kualitas baik, meski naik turun dan penuh tikungan. Terdapat sekitar 150 rumah di dusun ini. Desa Sampang sendiri berpenduduk lebih dari 2.000 jiwa dengan 1.805 orang diantaranya terdaftar sebagai pemilih dalam daftar pemilih tetap pilpres 2014 lalu seperti dipublikasikan KPU (Komisi Pemilihan Umum).

Gambar 2. Panorama dusun Jemblung, desa Sampang (Banjarnegara) dari langit dalam citra Google Earth pra bencana. Nampak bentangan jalan raya Banjarnegara-Dieng/Banjarnegara-Pekalongan, sungai Petir dan masjid al-Iman. Sumber: Sudibyo, 2014 dengan basis Google Earth.

Situasi berubah dramatis pada pukul 17:00 WIB. Didahului suara mirip ledakan keras hingga dua kali, lereng sisi utara Gunung Telagalele yang persis ada di hadapan dusun ini mendadak longsor. Materialnya mengalir deras tak tertahankan ke kaki gunung. Hampir segenap dusun beserta penduduknya kontan terkubur di bawah timbunan lumpur tebal. Longsor dahsyat ini juga menimbun jalan raya beserta kendaraan apapun yang sedang melintasinya saat itu. Hanya dalam lima menit, lansekap yang semula indah kini berubah menjadi timbunan tanah yang mengerikan. Luas kawasan yang terkena hantaman longsor dalam bencana dahsyat ini mencapai tak kurang dari 15 hektar dan sebagian menyumbat Sungai Petir, salah satu anak sungai Merawu dalam DAS (daerah aliran sungai) Serayu. Hingga Minggu 13 Desember 2014 TU, tim evakuasi yang kini sudah beranggotakan lebih dari 2.000 orang dari segenap eksponen relawan telah menemukan 42 jasad korban. Dari perkiraan 108 jasad yang terkubur, maka masih ada 66 orang yang belum ditemukan. Ribuan penduduk baik dari desa Sampang maupun desa-desa sekitarnya telah diungsikan ke tempat-tempat pengungsian sementara, seiring Gunung Telagalele dan bukit-bukit lainnya di sini yang masih labil. Nama Jemblung dan Sampang pun sontak menjadi episentrum perhatian hingga skala nasional.

Lempung dan Napal

Skala kedahsyatan bencana longsor Jemblung (Sampang) 2014 ini menggamit kembali ingatan akan sejumlah bencana sejenis yang menerpa Banjarnegara dalam setengah abad terakhir. Misalnya bencana longsor Gunungraja (Sijeruk) 2006, yang terjadi pada 4 Januari 2006 TU dan merenggut 90 nyawa dengan 76 jasad korban berhasil ditemukan dan 14 sisanya tetap hilang. Atau bencana longsor Legetang (Kepakisan) 1955 yang spektakuler, yang terjadi pada 16 April 1955 TU akibat ambrolnya lereng Gunung Pengamun-amun di Dataran Tinggi Dieng dan menimbun tak kurang dari 351 orang. Ketiga bencana longsor dahsyat itu pun harus disandingkan pula dengan bencana longsor dalam skala yang lebih kecil lainnya di Banjarnegara. Dalam kurun lima tahun terakhir, kabupaten ini berhadapan dengan 15 peristiwa tanah longsor atau rata-rata tiga peristiwa longsor per tahun. Semua bencana longsor menimbulkan kerugian material yang besar dan beberapa diantaranya bahkan merenggut korban jiwa, meski tak sefantastis bencana longsor dahsyat Legetang, Gunungraja dan Jemblung. Pada saat yang sama dengan bencana longsor dahsyat Jemblung ini, Banjarnegara pun sedang berhadapan dengan tak kurang dari 66 titik longsor lainnya.

Mengapa bencana tanah longsor seakan jadi penyakit kambuhan bagi Banjarnegara?

Gambar 3. Panorama dusun Jemblung, desa Sampang (Banjarnegara) dalam citra Google Earth pra bencana ke arah timur-timur laut. Tanda panah kuning menunjukkan arah gerakan tanah saat bencana longsor dahsyat 12 Desember 2014 TU. Sementara garis putus-putus menandakan perkiraan batas daerah yang tertimbun tanah dalam bencana tersebut. Sumber: Sudibyo, 2014 dengan basis Google Earth.

Faktor utamanya terletak pada geologi Banjarnegara yang unik, khususnya kawasan Karangkobar-Merawu yang menjadi bagian sub-DAS Merawu. Kawasan ini merupakan bagian dari mandala Pegunungan Serayu Utara yang topografinya relatif bergelombang yang lereng-lerengnya setengah terjal hingga terjal. Segenap kecamatan Karangkobar terletak di dalam pegunungan ini, dengan gunung-gunungnya memiliki kemiringan lereng antara 15 hingga 40 %. Kawasan Karangkobar-Merawu ini dialasi oleh batuan sedimen lempung dan napal hasil rombakan gunung berapi jauh di masa silam. Permukaannya ditutupi tanah hasil pelapukan yang cukup tebal. Hal ini masih ditambah dengan tercabik-cabiknya kawasan Karangkobar-Merawu akibat aktivitas tektonik nun jauh di masa silam, yang membuat kawasan ini dibelah-belah dan ditekan hebat demikian rupa oleh beragam sesar (patahan) yang saling bersilang-siur dan aktif pada masanya. Kini sesar-sesar itu telah lama mati, namun imbasnya masih bisa dirasakan dalam wujud rapuhnya lempung dan napal yang mengalasi kawasan Karangkobar-Merawu. Lempung dan napal tersebut cukup sarang sehingga mampu menyimpan air namun juga membuatnya mudah longsor bila kandungan airnya telah jenuh.

Kekhasan ini masih ditambah dengan terus bergeraknya kawasan Karangkobar-Merawu akibat desakan dari dalam dari arah selatan. Desakan yang masih terus berlangsung membuat lempung dan napal seakan diremas-remas. Sejumlah gunung batu relatif padat, yang adalah sisa intrusi magmatik nun jauh di masa silam dan relatif tahan terhadap pengikisan oleh cuaca, pun turut terdorong oleh desakan tersebut hingga terputus dari akarnya. Situasi ini kian menambah rapuh lempung dan napal di segenap kawasan Karangkibar-Merawu. Tak heran jika tingkat erosi di sini demikian tinggi, bahkan meskipun vegetasi (tumbuhan) berkayu yang rapat masih menutupi lereng-lerengnya dengan baik. Tanah pucuk (topsoil) yang dihanyutkan air lantas mengalir ke sungai-sungai kecil yang menjadi bagian sub-DAS Merawu. Hampir tiga perempat abad silam geolog legendaris van Bemmelen menyebut Sungai Merawu adalah sungai paling berlumpur di Indonesia. Tingginya erosi di sub-DAS Merawu memberikan kontribusi cukup besar bagi sedimentasi Waduk Panglima Besar Sudirman. Setiap tahunnya waduk ini dimasuki sedimen sebanyak 2,4 juta meter kubik. Sedimentasi tersebut setara dengan lumpur/tanah yang diangkut 1.300 dump truck kapasitas 5 meter kubik dalam setiap harinya. Selain erosi yang sangat tinggi, kekhasan kawasan Karangkobar-Merawu juga menjadikannya kawasan yang sangat rentan terhadap bencana tanah longsor baik dalam skala kecil maupun besar. Tak heran jika PVMBG (Pusat Vulkanologi dan Mitigasi Bencana Geologi) menempatkan mayoritas kecamatan Karangkobar ke dalam zona kerentanan gerakan tanah menengah (zona kuning) dan tinggi (zona merah).

Gambar 4. Peta zona kerentanan gerakan tanah untuk kecamatan Karangkobar dan sekitarnya dari Pusat Vulkanologi dan Mitigasi Bencana Geologi. Lingkaran merah menunjukkan lokasi bencana tanah longsor dahsyat Jemblung (Sampang) 2014. Nampak lokasi bencana dan sekitarnya didominasi oleh zona rentan gerakan tanah menengah (zona kuning) dan zona rentan gerakan tanah tinggi (zona merah). Sumber: PVMBG, t.t.

Bencana tanah longsor dahsyat di kawasan Karangkobar-Merawu umumnya disebabkan akumulasi air hujan dalam lereng setengah terjal hingga terjal sampai mencapai titik jenuh. Selain menambah bobot lereng, akumulasi air juga membuat bagian bawah tanah lereng tersebut seakan dilumasi sehingga menciptakan bidang gelincir. Begitu lereng tak lagi sanggup menahan bobotnya sendiri, bidang gelincir membuat proses melorotnya lereng menjadi lebih mudah. Jika bidang gelincirnya berbentuk cekung, maka tanah longsor bertipe rotasional pun terjadilah. Longsor rotasional cukup khas karena mengandung energi besar sehingga saat segenap lereng merosot, ia mampu meloncatkan kaki lereng (lidah longsor) hingga beberapa puluh atau bahkan beberapa ratus meter dalam kecepatan cukup tinggi sebelum menyentuh tanah. Sementara puncak lereng (mahkota longsor) mungkin hanya beringsut beberapa meter hingga beberapa puluh meter. Loncatan ini sangat sulit dihindari. Namun bencana tanah longsor dalam skala besar tidaklah terjadi sekonyong-konyong. Selalu terdapat gejala pendahuluan sebelum peristiwa utamanya terjadi, dalam rupa terbentuk retakan-retakan di bagian atas lereng yang kemudian terus berkembang memanjang dan kian dalam menjadi retakan lengkung/retakan bulan sabit/retakan tapal kuda. Dari retakan inilah air hujan lebih mudah memasuki lereng dan terakumulasi. Tatkala hal ini sudah terjadi, bencana tanah longsor tinggal menunggu waktu.

Gambar 5. Tiga lokasi dalam Kabupaten Banjarnegara yang pernah dilanda bencana tanah longsor dahsyat hingga melenyapkan hampir segenap dusun. Masing-masing adalah dusun Legetang desa Kepakisan (kecamatan Batur), dusun Gunungraja desa Sijeruk (kecamatan Banjarmangu) dan dusun Jemblung desa Sampang (kecamatan Karangkobar). Sumber: Sudibyo, 2014 dengan basis Google Earth.

Legetang dan Gunungraja

Hal tersebut teramati dalam bencana tanah longsor dahsyat Legetang 1955. 70 hari sebelum bencana terjadi, retakan sudah mulai terlihat di dekat puncak Gunung pengamun-amun (elevasi 2.000 meter dpl) yang berjarak sekitar 500 meter sebelah timur dusun Legetang, desa Kepakisan. Para pencari rumput dan kayu bakar di gunung yang saat itu tertutupi hutan lebat pun telah mengetahuinya. Kian lama retakan tersebut kian melebar dan juga kian dalam, mengarah ke sisi tenggara. Retakan yang terus berkembang ini sering menjadi bahan obrolan sehari-hari penduduk dusun Legetang, yang terletak pada elevasi sekitar 1.800 meter dpl. Namun tak ada yang merasa khawatir atau menduga terlalu jauh.

Situasi berubah dramatis pada pertengahan April 1955 TU. Setelah diguyur hujan lebat selama berhari-hari, lereng sisi tenggara Gunung Pengamun-amun telah demikian berat dan terlumasi dasarnya sehingga merosot ambrol dalam volume sangat besar. Penyelidikan geolog MM Purbo dari Jawatan Geologi (kini Badan Geologi Kementerian Energi dan Sumber Daya Mineral RI) memperlihatkan kombinasi longsor bertipe rotasional dengan halangan bukit kecil dihadapannya membuat membuat lidah longsor meloncat jauh. Ia membentur bukit dihadapannya. Hingga akhirnya material longsor pun terbelokkan ke dusun Legetang setelah meloncati sebatang sungai kecil jelang tengah malam 16 April 1955 TU. Segenap dusun ini pun terkubur di bawah tumbunan tanah yang sangat tebal beserta 332 penduduknya dan 19 orang dari desa lain yang sedang bertamu ke dusun tersebut.

Gambar 6. Bagaimana bencana tanah longsor dahsyat Legetang (Kepakisan) 1955 terjadi, dalam ilustrasi berbasis citra Google Earth. Saat lereng tenggara Gunung Pengamun-amun hingga hampir ke puncaknya merosot dengan tipe rotasional (panah kuning tak terputus), materialnya segera membentur bukit dihadapannya. Sehingga berbelok arah menjadi mengubur dusun Legetang (panah kuning putus-putus). 351 orang tewas dan hanya 1 jasad yang berhasil dievakuasi. Sumber: Sudibyo, 2014 dengan basis Google Earth dan Abdrurrahman, 2013.

Bentang lahan Legetang pun berubah dramatis dari semula cekungan di sebuah lembah menjadi gundukan sedikit membukit. Dari 351 korban jiwa itu, hanya jasad kepala dusun yang berhasil dievakuasi. Sisanya terlalu sulit untuk digali akibat tebalnya timbunan tanah. Bencana dahsyat ini sontak menggemparkan masyarakat Banjarnegara khususnya di Dataran Tinggi Dieng. Penduduk segera menghubung-hubungkan bencana ini dengan sikap warga dusun Legetang, yang jauh dari kehidupan religius. Kini di ‘bukit’ yang menimbun Legetang terdapat sebuah tugu beton sebagai pengingat akan bencana yang paling mematikan di Dataran Tinggi Dieng dan Banjarnegara.

Hal serupa juga terjadi jelang bencana longsor dahsyat Gunungraja. Bahkan retakan di lereng bukit Pawinihan sudah terdeteksi semenjak 2004, atau dua tahun sebelumnya. Retakan tersebut terus berkembang dan melebar akibat erosi parit. Hingga dua minggu jelang bencana, retakan ini telah sepanjang 25 meter dengan lebar 1 hingga 2 meter sedalam 4 meter. Lebih tak menguntungkan lagi, erosi parit juga membuat ujung parit ini terbendung oleh material erosi sehingga air tak leluasa mengalir. Namun sepanjang waktu itu tidak ada langkah antisipasi. Meski demikian hingga November 2005 TU bencana relatif terhindarkan seiring masih seimbangnya arus keluaran air (lewat kemampuan tanah bukit untuk menyerap air) dengan arus masukan air (dari air hujan).

Situasi berubah dramatis pada November 2005 TU saat tanah di kaki bukit diperkeras dengan aspal sebagai jalan raya lokal yang menghubungkan dusun Gunungraja Wetan dengan dusun Kendaga, keduanya dalam wilayah desa Sijeruk. Pengaspalan jalan lokal ini jelas bertujuan baik, untuk memperlancar arus transportasi setempat dengan efek multidimensinya. Namun dalam analisis pascabencana yang dilakukan tim Dewan Riset Daerah (DRD) Jawa Tengah, pengaspalan jalan di kaki bukit membuat keseimbangan terganggu. Kini arus masukan air menjadi lebih besar dari arus keluarannya. Puncaknya terjadi pada selang waktu antara 27 Desember 2005 hingga 4 Januari 2006 TU, saat Banjarnegara diguyur hujan lebat. Masukan air di lereng bukit Pawinihan itu pun meningkat hebat tanpa diimbangi oleh peningkatan kemampuan keluaran air. Lereng yang jenuh air membuat bobotnya bertambah besar sembari menciptakan bidang gelincir didasarnya. Maka bencana tanah longsor dahsyat pun terjadilah, tak peduli bahwa lereng bukit itu masih tertutupi tumbuh-tumbuhan berakar tunggang dengan baik. Sebagian dusun Gunungraja pun lenyap di bawah timbunan tanah, yang merenggut nyawa 90 orang dari sekitar 600 orang penduduknya.

Gambar 7. Bagaimana bencana tanah longsor dahsyat Gunungraja (Sijeruk) 2006 terjadi, dalam ilustrasi berbasis citra Google Earth. Saat lereng timur Bukit Pawinihan merosot dengan tipe rotasional (panah kuning)materialnya segera meloncat dan mengubur dusun Gunungraja. 90 orang tewas dan 76 jasad yang berhasil dievakuasi. Sumber: Sudibyo, 2014 dengan basis Google Earth dan data dari Sutopo & Wilonoyudho, 2006.

Bagaimana dengan longsor dahsyat Jemblung?

Relawan MDMC (Muhammadiyah Disaster Management Centre) yang sempat melakukan assessment sebelum bencana menyebutkan telah ada retakan di lereng utara Gunung Telagalele semenjak sebulan sebelum bencana. Retakan tersebut bahkan telah berkembang seiring datangnya musim penghujan. Berkaca dari pengalaman longsor dahsyat Gunungraja, yang hanya berjarak 5 kilometer di selatan dusun Jemblung, maka sejumlah langkah antisipasi telah dilakukan. Penduduk yang bermukim di rumah-rumah yang persis ada di bawah retakan pun telah dievakuasi. Dapat dikatakan bahwa penduduk dusun Jemblung telah mengetahui potensi longsor tersebut dan telah melakukan antisipasi. Satu hal yang belum jelas benar adalah seberapa jauh longsor yang bakal terjadi itu melanda. Anggapan yang berkembang, longsor yang bakal terjadi mungkin berskala kecil hingga sedang. Sehingga evakuasi hanya dilakukan di rumah-rumah di lereng, yang posisinya paling dekat ke retakan.

Asumsi ini ternyata tak terbukti. Longsor yang benar-benar terjadi ternyata berskala besar. Analisis tim respon cepat bencana UGM (Universitas Gadjah Mada) menyebut lereng yang longsor berdimensi tinggi 100 meter dan lebar 500 meter. Tipe longsornya mungkin rotasional, yang membuat lidah longsor meloncat dan menerjang hingga sejauh 600 meter. 35 rumah dan 1 masjid (Masjid al-Iman) bersama dengan penggal jalan raya Banjarnegara-Dieng tertimbun material longsor hingga bermeter-meter. Dari 308 penduduknya, 200 orang diantaranya berhasil menyelamatkan diri. Longsor dahsyat Jemblung merupakan yang terbesar di antara 34 titik tanah longsor lainnya yang berhasil ditemukan. Seluruhnya terletak di kawasan Karangkobar.

Gambar 8. Panorama dusun Jemblung, desa Sampang (Banjarnegara) dan Gunung Telagalele dalam ilustrasi berbasis citra Google Earth dengan arah pandang ke selatan. Garis putus-putus menunjukkan perkiraan posisi asal material longsor. Tanda panah kuning menunjukkan arah gerakan tanah dalam bencana longsor dahsyat tersebut. Sumber: Sudibyo, 2014 dengan basis Google Earth dan keterangan Azizah, 2014.

Pasca bencana, tim kaji cepat yang beranggotakan UGM, BMKG, PVMBG, LIPI (Lembaga Ilmu Pengetahuan Indonesia), BNPB (Badan Nasional Penanggulangan Bencana) dan lainnya memperlihatkan potensi bencana masih tetap membayangi dusun Jemblung ke depan. Potensi pertama datang dari material longsoran yang sebagian membendung sungai Petir. Jika hujan deras, bendungan ini akan menghalangi air sungai untuk beberapa saat sebelum kemudian jebol menjadi banjir bandang. Sementara potensi kedua datang dari mahkota longsor. Di sini terdapat telaga sepanjang 30 meter yang digenangi air hingga sedalam 1 meter. Bila hujan deras kembali mengguyur, air dalam telaga ini dapat menekan tanah dibawahnya yang telah demikian lunak dan rapuh sehingga longsor dapat kembali terjadi. Bahkan dalam prediksi terburuk, skala bencananya bisa melampaui apa yang barusan dusun Jemblung alami!

Antisipasi

Dalam bencana tanah longsor pada umumnya, sedikitnya ada tiga faktor yang berkontribusi. Dalam kasus Banjarnegara khususnya di kawasan Karangkobar-Merawu, faktor pertama adalah kondisi geologi yang unik. Faktor kedua adalah hujan deras hingga hujan ekstrim. Dan faktor ketiga adalah tersumbatnya drainase sehingga air tidak bisa terbebas dengan leluasa dari lereng yang berpotensi longsor. Faktor pertama dan kedua adalah faktor yang terberi (given), atau sudah dari sononya demikian. Sehingga tak bisa dikendalikan manusia. Namun berbeda dengan faktor ketiga. Manusia dapat mengelola drainase lereng, sehingga tingkat kejenuhan airnya dapat direduksi. Saluran-saluran drainase sederhana dapat dibangun untuk keperluan itu. Di samping itu retakan yang sudah terbentuk harus segera ditimbuni lagi hingga rata. Juga tak boleh ada penggalian baik di lereng maupun kaki lereng, baik kecil-kecilan apalagi besar, atas alasan apapun.

Gambar 9. Citra medan pandang lebar (wide-field) lokasi bencana tanah longsor dahsyat Jemblung (Sampang) 2014, diambil Pusat Vulkanologi dan Mitigasi Bencana Geologi per 13 Desember 2014 TU. Arah pandang ke selatan-tenggara. Nampak posisi mahkota longsor dan telaga/genangan air tepat dibawahnya. Sumber: PVMBG, 2014.

Bencana tanah longsor senantiasa membayangi Banjarnegara sebagai implikasi dari takdir kembumiannya yang unik. Takdir yang membuat tanah di sini sangat subur dan dapat ditumbuhi beragam tanaman budidaya. Takdir yang juga menjadikannya kawasan berpanorama indah dan sejuk. Jika dikelola dengan baik, dua hal tersebut dapat menjadikan Banjarnegara gemah ripah loh jinawi. Namun high risk high gain, di balik segala keuntungan tersebut tersembunyi pula bakat marabahaya. Di masa beratus hingga ribuan tahun silam, potensi bencana tanah longsor mungkin tak menjadi masalah besar seiring jumlah penduduk yang masih jarang. Namun kini jumlah penduduk telah berlipat ganda, sehingga resikonya semakin besar. Maka patut disambut baik upaya tim UGM beserta institusi lainnya untuk memetakan potensi longsor Banjarnegara hingga ke tingkat dusun (sub-desa). Patut disambut pula gagasan gubernur Jawa Tengah untuk menransmigrasikan lokal penduduk dusun Jemblung yang masih tersisa. Gagasan transmigrasi lokal atau relokasi yang masih tetap berada dalam lingkup Banjarnegara patut dikembangkan tak hanya untuk dusun Jemblung pasca bencana. Namun juga untuk dusun-dusun lain yang kelak diketahui memiliki potensi longsor yang tinggi. Agar kelak korban tak lagi berjatuhan…

Bahan acuan :

1. Oman Abdurrahman. 2013. Geologi Linewatan, dari Tasikmalaya hingga Banjarnegara. Geomagz, vol. 3 no. 1 (Maret 2013), hal. 54-79.
2. PVMBG. 2014. Tanggapan Bencana Gerakan Tanah Di Kecamatan Sigaluh, Kecamatan Pejawaran dan Kecamatan Karang Kobar, Kabupaten Banjarnegara, Provinsi Jawa Tengah. Pusat Vulkanologi dan Mitigasi Bencana Geologi, Badan Geologi, Kementerian Energi dan Sumber Daya Mineral RI, 12 Desember 2014.
3. Buku Putih Sanitasi Kabupaten Banjarnegara. 2011.
4. Sutopo & Wilonoyudho. 2006. Analisis Tanah Longsor Banjarnegara. Wacana Suara Merdeka, 26 Januari 2006.
5. Daryono. 2014. komunikasi personal.
6. Ima Azizah. 2014. komunikasi personal.
7. Twitter Nurmansyah (@nurmansali). 2014.
8. Detik. 2014. Ini Hasil Investigasi UGM soal Aspek Geologi Bencana Longsor Banjarnegara. Laman DetikNews, reportase Sukma Indah Permana, 15 Desember 2014.
9. Tempo. 2014. Kolam Raksasa pada Sumber Longsor Banjarnegara. Laman Tempo.co, reportase Aris Andrianto, 15 Desember 2014.

sumber : https://ekliptika.wordpress.com


Powerful landslides Jemblung and Fate of Earth Banjarnegara

Twilight before arriving at all Banjarnegara district, Central Java province, on Friday, December 12th, 2014 Public Date (TU) ago. Under normal conditions the panorama will amaze anyone, when the sky gradually became flushed copper at a time when the Sun flushed and faded, scenery always gave the impression of spiritual and religious. But that afternoon none could be seen. Even a beam of sunlight is not too visible. Banjarnegara being rained on. Water droplets torrential rain dampen all the districts since the previous day. Class III Banjarnegara geophysical stations operated by BMKG (Meteorology and Geophysics) recorded rainfall throughout Thursday, December 11th, 2014 TU reached 112.7 millimeters. And a day later rainfall still amounted to 101.8 millimeters. In two days the intensity of rain which flushed throughout Banjarnegara of 214.5 millimeters. In times past, in general rainfall as much as it takes a full month in December (on average) in all Banjarnegara sentenced. Clearly, with the volume of rain water equivalent to the average poured for 31 full days, it rained the whole 11 to December 12, 2014 in Banjarnegara qualified heavy rain or extreme rainfall.

Figure 1. Face Jemblung hamlet, village Sampang (Banjarnegara) between before and after the devastating landslide December 12, 2014 TU. Pre-disaster imagery taken from the north side of highway-Dieng Banjarnegara facing northwest-north. It appears al-Iman mosque in the background. While post-disaster imagery taken from a higher location, but not how far from the location of the image before the disaster, with the same viewing direction. It appears all been turned into a pile of mud. Source: Nurmansyah, 2014.

Figure 1. Face Jemblung hamlet, village Sampang (Banjarnegara) between before and after the devastating landslide December 12, 2014 TU. Pre-disaster imagery taken from the north side of highway-Dieng Banjarnegara facing northwest-north. It appears al-Iman mosque in the background. While post-disaster imagery taken from a higher location, but not how far from the location of the image before the disaster, with the same viewing direction. It appears all been turned into a pile of mud. Source: Nurmansyah, 2014.

The torrential rain made the whole Banjarnegara shivering and hoping against hope. Overflow news Serayu, the main river in the district, while drain current was so swift spread everywhere. River water is so abundant that the water level in the reservoir Panglima Sudirman (Mrica), which exist in the watershed Serayu, also reached a maximum within a short time. As a result, managers are forced to open the doors pelimpas water (spillway) was to maintain the security of the weir. Water was menderas Serayu downstream and could submerge several homes. Berkeruncingan no news had spread everywhere, preaching the reservoir has to give way and submerge downstream although this quickly denied by the dam manager. The points landslides were emerging everywhere in the district. But the worst has not yet come.

On Friday evening the majority of villagers Jemblung, Sampang village, subdistrict Karangkobar prefer meriung in each residence. Torrential rains that day just passed. But the water droplets are softer still falling, making people reluctant to come out. Simple hamlet cool air that lies at an elevation of 930 to 940 meters above sea level (paras seawater from the average). The majority of the population worked in the agricultural world. Hamlet is hardly known outside Karangkobar, despite being in the path of the main highway connecting the city with Leksana Banjarnegara (capital district Karangkobar) and Dieng Plateau. The same highway also became one of the connecting shaft Banjarnegara with Pekalongan in the north. The road has been paved smooth with good quality, despite ups and downs and full of twists. There are about 150 houses in this village. Sampang village itself has a population of more than 2,000 people with 1,805 of them are registered as voters in the 2014 presidential election voters list and as published KPU (General Election Commission). 

Figure 2. Panorama Jemblung hamlet, village Sampang (Banjarnegara) from the sky in Google Earth image of the pre-disaster. Visible stretch of highway Banjarnegara-Dieng / Banjarnegara-Pekalongan, river Lightning and the mosque of al-Iman. Source: Sudibyo, 2014 on the basis of Google Earth.

The situation changed dramatically at 17:00 pm. Sounds like a loud explosion preceded by two times, the slopes of the northern side of Mount Telagalele who exactly is in front of this village sudden landslides. The material flowing unbearable to the foot of the mountain. Almost the entire village and its inhabitants in cash buried under thick mud. The massive landslide also stockpiled along the highway any vehicle that is being crossed at that time. Only in five minutes, which was originally a beautiful landscape is now turned into a terrible barrow. Broad areas hit by landslides in this terrible disaster reached no less than 15 acres and partially clog Lightning River, one of the tributaries in the watershed Merawu (watershed) Serayu. Until Sunday, December 13th, 2014 TU, evacuation team now consists of more than 2,000 people of all exponents of volunteers have found 42 bodies. Of the estimated 108 bodies were buried, then there are 66 people who have not been found. Thousands of residents of both villages Sampang and surrounding villages have been evacuated to temporary refugee camps, as Mount Telagalele and other hills here are still unstable. Sampang Jemblung name and also instantly became the epicenter of attention to national scale.



Clay and marl

Jemblung awesomeness scale landslides (Sampang) 2014 took her back memories of a similar disaster that hit Banjarnegara in the last half century. For example landslides Gunungraja (Sijeruk) in 2006, which occurred on January 4, 2006 TU and claimed 90 lives with 76 bodies of the victims have been found and the remaining 14 remained missing. Or landslides Legetang (Kepakisan) 1955 spectacular, which occurred on 16 April 1955 TU result ambrolnya slopes of Mount Pengamun-Amun in the Dieng Plateau and hoards no less than 351 people. Third devastating landslides that have to be juxtaposed with the landslide also in other smaller scale in Banjarnegara. In the last five years, the district is faced with 15 events landslides or an average of three events per year landslides. All landslides causing huge material losses and some of them even claimed lives, although not massive landslide disaster sefantastis Legetang, Gunungraja and Jemblung. At the same time with this Jemblung devastating landslides, Banjarnegara also was dealing with no less than 66 point other landslides.

Why landslides seemed so recurrent disease for Banjarnegara?


Figure 3. Panorama Jemblung hamlet, village Sampang (Banjarnegara) in Google Earth imagery pre-disaster to the east-northeast. The yellow arrow indicates the direction of movement of the ground when the landslide devastating December 12, 2014 TU. While the dotted line indicates the approximate boundaries are buried in the ground in the area of the disaster. Source: Sudibyo, 2014 on the basis of Google Earth.

Figure 3. Panorama Jemblung hamlet, village Sampang (Banjarnegara) in Google Earth imagery pre-disaster to the east-northeast. The yellow arrow indicates the direction of movement of the ground when the landslide devastating December 12, 2014 TU. While the dotted line indicates the approximate boundaries are buried in the ground in the area of the disaster. Source: Sudibyo, 2014 on the basis of Google Earth.



The key factor lies in its unique geological Banjarnegara, especially Karangkobar-Merawu region which became part of sub-watershed Merawu. This area is part of the mandala Mountains North Serayu relatively undulating topography slopes are steep to steep half. All the sub-district is located in the mountains Karangkobar this, the mountains have a slope of between 15 and 40%. Region-Merawu Karangkobar is covered by sedimentary clay and marl result destruction volcano long ago. Its surface is covered soil weathering results are quite thick. This was coupled with torn him to pieces Karangkobar-Merawu region due to tectonic activity far in the past, which makes this region split apart and thus such a great suppressed by various faults (fault) crossed-maze and active in his time. Now the fault-fault had been long dead, but the impact can still be felt in the form of the fragility of clay and marl which lay a Karangkobar-Merawu region. Clay and marl is pretty nest so as to save water, but also makes it easy to landslides when the water content has been saturated.



This peculiarity was coupled with continued movement Karangkobar-Merawu region due to pressure from inside of the south. Insistence that continues making clay and marl as knead. A number of relatively solid rock, which is the rest of the magmatic intrusion far in the past and are relatively resistant to erosion by the weather, was also driven by the insistence to cut off from its roots. This situation adds to the fragile clay and marl in all Karangkibar-Merawu region. No wonder the attrition rate so high here, even though the vegetation (plants) dense woody still covered slopes well. Top soil (topsoil), which swept away the water then flows into streams that are part of a sub-watershed Merawu. Nearly three-quarters of a century ago, the legendary geologist van Bemmelen call Merawu River is the most muddy river in Indonesia. The high erosion in the sub-watershed Merawu make a significant contribution to the sedimentation of reservoirs Panglima Sudirman. Each year these reservoirs penetrated sediments of 2.4 million cubic meters. Sedimentation is equivalent to mud / soil dump trucks transported 1,300 cubic meters capacity 5 in every day. In addition to very high erosion, distinctiveness Karangkobar-Merawu region also makes the region highly vulnerable to landslides both in small and large scale. No wonder if PVMBG (Center for Volcanology and Geological Hazard Mitigation) puts the majority of sub-districts Karangkobar into the middle ground motion vulnerability zone (yellow zone) and high (red zone).


Figure 4. Map of the zone of ground movement susceptibility to sub-district and surrounding Karangkobar of the Center for Volcanology and Geological Hazard Mitigation. The red circle shows the location of the devastating landslides Jemblung (Sampang) in 2014. It appears the disaster site and surrounding areas are dominated by middle ground motion vulnerable zones (yellow zone) and high ground motion vulnerable zones (red zone). Source: PVMBG, t.t.



Figure 4. Map of the zone of ground movement susceptibility to sub-district and surrounding Karangkobar of the Center for Volcanology and Geological Hazard Mitigation. The red circle shows the location of the devastating landslides Jemblung (Sampang) in 2014. It appears the disaster site and surrounding areas are dominated by middle ground motion vulnerable zones (yellow zone) and high ground motion vulnerable zones (red zone). Source: PVMBG, t.t.



Devastating landslides in the region Karangkobar-Merawu usually caused accumulation of rain water in half steep slope to steep until it reaches saturation point. In addition to add weight to the slopes, the accumulation of water also makes the bottom of the slope the ground as if lubricated thereby creating a sliding plane. Once the slope is no longer able to hold its own weight, sliding plane making process melorotnya slope becomes easier. If the field gelincirnya concave, then the type of rotational landslides were there. Rotational landslide quite distinctive because they contain large energy so that when the entire slope slump, he was able to meloncatkan foot slope (landslide tongue) to a few tens or even a few hundred meters in the high speed before it hits the ground. While the top of the slope (landslide crown) might just edged a few meters to a few tens of meters. Springboard is very difficult to avoid. However landslides on a large scale does not happen suddenly. Always there is a preliminary symptoms before the main event occurred, in the likeness of cracks formed at the top of the slope and then evolving into becoming increasingly elongated and curved cracks / fissures crescent / cracks horseshoe. Rainwater from these cracks more easily into the slope and accumulated. When this has happened, landslides a matter of time.

Figure 5. Three locations in Banjarnegara has been hit by devastating landslides to the exclusion of almost all village. Each is a hamlet village Legetang Kepakisan (Batur subdistrict), hamlet village Gunungraja Sijeruk (subdistrict Banjarmangu) and hamlet village Jemblung Sampang (subdistrict Karangkobar). Source: Sudibyo, 2014 on the basis of Google Earth.

Figure 5. Three locations in Banjarnegara has been hit by devastating landslides to the exclusion of almost all village. Each is a hamlet village Legetang Kepakisan (Batur subdistrict), hamlet village Gunungraja Sijeruk (subdistrict Banjarmangu) and hamlet village Jemblung Sampang (subdistrict Karangkobar). Source: Sudibyo, 2014 on the basis of Google Earth.

Legetang and Gunungraja

It is observed in the devastating landslides Legetang 1955. 70 days before the disaster occurs, cracks have started to appear near the top of Mount pengamun-Amun (elevation 2,000 meters above sea level) which is about 500 meters east of the hamlet Legetang, Kepakisan village. The search of grass and firewood in the mountains when it was covered with dense forests already know. Increasingly these cracks widening and deepening, leading to the southeast. This growing cracks are often the subject of everyday conversation Legetang villagers, which is located at an elevation of about 1,800 meters above sea level. But there's nothing to worry or suspect too far.

The situation changed dramatically in mid-April 1955 TU. After heavy rain for days, southeast side slopes of Mount Pengamun-Amun was so heavy and so basically lubricated slumped collapsed in very large volumes. MM geologist investigation Purbo of Geology Bureau (now the Geological Agency of the Ministry of Energy and Mineral Resources) shows the type of rotational landslide combination with obstruction of a small hill in front of him making a tongue landslide jump away. He hit the hill in front. Until finally landslide material was deflected to the village after the jump over a river Legetang little ahead of midnight 16 April 1955 TU. The whole village was buried under the ground tumbunan very thick along with 332 residents and 19 people from other villages that are a visit to the village.

Figure 6. How devastating landslides Legetang (Kepakisan) 1955 occurs, the Google Earth image based illustration. When the southeastern slopes of Mount Pengamun-Amun up almost to the top with the type of rotational slump (unbroken yellow arrows), the material immediately hit the hill in front of him. So turn towards being buried hamlet Legetang (dashed yellow arrows). 351 people were killed and only one body of which had been evacuated. Source: Sudibyo, 2014 on the basis of Google Earth and Abdrurrahman, 2013.

Figure 6. How devastating landslides Legetang (Kepakisan) occurred in 1955, the Google Earth image based illustration. When the southeastern slopes of Mount Pengamun-Amun up almost to the top with the type of rotational slump (unbroken yellow arrows), the material immediately hit the hill in front of him. So turn towards being buried hamlet Legetang (dashed yellow arrows). 351 people were killed and only one body of which had been evacuated. Source: Sudibyo, 2014 on the basis of Google Earth and Abdrurrahman, 2013.

Legetang landscape changed dramatically from its original basin in a valley into a little mound of a hill. Of the 351 fatalities, the only remains of the village head had been evacuated. The rest is too difficult to be extracted due to the thickness of soil deposits. This terrible disaster torn communities Banjarnegara particularly shocking in the Dieng Plateau. Residents immediately attributed the disaster to the attitude of villagers Legetang, which is far from the religious life. Now in the 'hill' that hoard Legetang there is a concrete monument as a reminder of the deadliest disasters in the Dieng Plateau and Banjarnegara.

It is also common Gunungraja massive landslide disaster ahead. Even cracks in the hillside Pawinihan been detected since 2004, or two years earlier. The cracks continue to grow and expand as a result of gully erosion. Up to two weeks ahead of the disaster, these cracks have a 25-meter with a width of 1 to 2 meters depth of 4 meters. More no longer profitable, gully erosion also makes it unstoppable by the end of the trench so that the erosion of material was freely flowing water. But all the time there was no anticipation. However until November 2005 TU relatively inevitable disaster as the output current unbalance still water (through the soil's ability to absorb water hill) with the input current of water (rain water).

The situation changed dramatically in November 2005 TU when the soil at the foot of the hill paved with asphalt as the local highway that connects the hamlet to hamlet Kendaga Gunungraja Wetan, both in rural areas Sijeruk. Local road paving is clearly aimed at both, to facilitate the flow of local transportation with multidimensinya effect. But in the post-disaster analysis by a team of Regional Research Council (DRD) Central Java, asphalting roads in the foothills making disturbed balance. Now the water input current becomes larger than the output current. The peak occurred during the year between December 27, 2005 until January 4, 2006 TU, when Banjarnegara heavy rain. Put water in the hillside Pawinihan it was a great increase without offset by increased water output capability. Water-saturated slope makes getting bigger weight while creating a sliding plane bottom. So devastating landslides were there, no matter that the hillside was still covered with vegetation roots riding well. Most hamlet Gunungraja disappeared under barrow, which claimed the lives of 90 people from around 600 inhabitants.

Figure 7. How devastating landslides Gunungraja (Sijeruk) 2006, there was, in Google Earth imagery based illustration. When the eastern slopes of Mount Pawinihan slump with a rotational type (yellow arrows) and bury the material immediately jumped Gunungraja hamlet. 90 people were killed and 76 bodies were successfully evacuated. Source: Sudibyo, 2014 on the basis of data from Google Earth and Sutopo & Wilonoyudho, 2006.

Figure 7. How devastating landslides Gunungraja (Sijeruk) 2006, there was, in Google Earth imagery based illustration. When the eastern slopes of Mount Pawinihan slump with a rotational type (yellow arrows) and bury the material immediately jumped Gunungraja hamlet. 90 people were killed and 76 bodies were successfully evacuated. Source: Sudibyo, 2014, Google Earth and the data base of Sutopo & Wilonoyudho 2006.

What about the massive landslide Jemblung?

Volunteers MDMC (Muhammadiyah Disaster Management Centre) who had time to do before disaster assessment mentions has no cracks on the northern slopes of Mount Telagalele since a month before the disaster. The cracks have even grown over the coming rainy season. Reflecting on the experience Gunungraja massive landslide, which is just 5 miles south of the hamlet Jemblung, then the amount of precaution has been done. Residents who live in houses just under the cracks were already evacuated. It can be said that the villagers Jemblung already know the potential for landslides and has anticipated. One thing that is not clear is how far it will happen landslide struck. Assumption that develops, landslides will happen maybe small to moderate. So that evacuation is only done in the houses on the slopes, the position closest to the cracks.

This assumption was not proven. Landslides that actually happens it turns out large scale. Analysis of disaster response teams UGM (Universitas Gadjah Mada) called high-dimensional avalanche slope of 100 meters and a width of 500 meters. Type of possible rotational landslide, which makes jumping and crashing avalanche tongue as far as 600 meters. 35 houses and one mosque (Masjid al-Iman) along with cut-Dieng Banjarnegara highway landslide material piled up to many meters. Of the 308 residents, 200 of them managed to escape. Jemblung massive landslide is the largest among the 34 point other landslides have been found. Entirely located in Karangkobar.

Figure 8. Panorama Jemblung hamlet, village Sampang (Banjarnegara) and Mount Telagalele in Google Earth imagery based illustration with the direction of view to the south. The dotted lines indicate the approximate position of the origin of landslide material. The yellow arrow indicates the direction of movement of soil in the devastating landslides. Source: Sudibyo, 2014 on the basis of Google Earth and information Azizah, 2014.

Figure 8. Panorama Jemblung hamlet, village Sampang (Banjarnegara) and Mount Telagalele in Google Earth imagery based illustration with the direction of view to the south. The dotted lines indicate the approximate position of the origin of landslide material. The yellow arrow indicates the direction of movement of soil in the devastating landslides. Source: Sudibyo, 2014 on the basis of Google Earth and information Azizah, 2014.

After a disaster, rapid assessment team consisting of UGM, BMKG, PVMBG, LIPI (Indonesian Institute of Sciences), BNPB (National Disaster Management Agency) and the other shows the potential for disaster is still overshadowing the hamlet Jemblung forward. The first comes from the potential avalanche of material that partially dam the river Lightning. If the heavy rain, this dam will block the river water for some time before then burst into a flood. While both come from the crown potential landslides. Here there is a 30-meter long lake that flooded to a depth of 1 meter. When the heavy rain back flushed, the water in this lake can hit the ground underneath that has been so soft and fragile, so landslides may re-occur. Even in the worst predictions, the scale of the disaster could go beyond what is natural Jemblung hamlet just now!

anticipation
In a landslide in general, there are at least three factors that contribute. In the case particularly in the area Banjarnegara Karangkobar-Merawu, the first factor is the unique geological conditions. The second factor is the heavy rain to extreme rainfall. And the third factor is the blockage of drainage so that water can not be free to freely from the slopes prone to landslide. The first and the second factor is the factor that terberi (given), or has from nature so. So that can not be controlled human. But unlike the third factor. Humans can manage drainage slope, so that the water saturation level can be reduced. Simple drainage channels can be constructed for this purpose. In addition, the cracks that have formed must immediately swamped again until blended. Also there should be no excavations both on the slopes and foot slopes, both large small moreover, for any reason.

Figure 9. The image of a wide field of view (wide-field) location devastating landslides Jemblung (Sampang) 2014, taken the Center for Volcanology and Geological Hazard Mitigation per December 13, 2014 TU. Direction of view to the south-southeast. It appears landslide crown position and pond / puddle right below it. Source: PVMBG, 2014.

Figure 9. The image of a wide field of view (wide-field) location devastating landslides Jemblung (Sampang) 2014, taken the Center for Volcanology and Geological Hazard Mitigation per December 13, 2014 TU. Direction of view to the south-southeast. It appears landslide crown position and pond / puddle right below it. Source: PVMBG, 2014.

Landslides continue to overshadow Banjarnegara as the implications of kembumiannya unique destiny. Destiny that makes the soil here is very fertile and can be covered a variety of crops. Fate which also makes scenic and cool area. If managed well, two things can make Banjarnegara gemah ripah jinawi tablets. However, high risk high gain, despite all these advantages are also hidden talent distress. In the hundreds to thousands of years ago, the potential landslides may not be a big problem as the number of people who are still rare. But now the population has doubled, so the risk is greater. Then it should be welcomed GMU team effort along with other institutions to identify potential landslide Banjarnegara up to the village level (sub-village). It is worth also welcomed the idea of the governor of Central Java to local villagers menransmigrasikan Jemblung remaining. The idea of local resettlement or relocation that still remain within the scope of Banjarnegara should be developed not only for post-disaster Jemblung hamlet. But also for other hamlets that later known to have a high potential for landslides. That in the future no longer fall victim ...

     References:

1. Oman Abdurrahman. 2013. Geology Linewatan, from Tasikmalaya to Banjarnegara. Geomagz, vol. 3 no. 1 (March 2013), p. 54-79.
2. PVMBG. 2014. Soil Movement Disaster Response In Sub Sigaluh, District Pejawaran and Karang Kobar, Banjarnegara, Central Java Province. Center for Volcanology and Geological Hazard Mitigation, Geological Agency, Ministry of Energy and Mineral Resources, December 12, 2014.
3. White Book Sanitation Banjarnegara. 2011.
4. Sutopo & Wilonoyudho. 2006. Analysis of Landslide Banjarnegara. Discourse Suara Merdeka, January 26, 2006.
5. Daryono. 2014. Personal communication.
6. Ima Azizah. 2014. Personal communication.
7. Twitter Nurmansyah (nurmansali). 2014.
8. Sec. Investigation Results UGM 2014. This matter Geological Aspects Landslide Banjarnegara. Page headline, reportage Sukma Beautiful Permana, December 15, 2014.
9. Tempo. 2014. Swimming Giant in Banjarnegara landslide source. Page Tempo.co, reportage Aris Andrianto, December 15, 2014.

source: https://ekliptika.wordpress.com