TIPOLOGI PEDOGEOMORFIK KEJADIAN LONGSORLAHAN DI PEGUNUNGAN KULONPROGO DAERAH ISTIMEWA YOGYAKARTA INDONESIA

Kuswaji Dwi Priyono, Drs.,M.Si., Dr. Sunarto, M.S

2012 | Disertasi | S3 Geografi

Penelitian disertasi ini dilaksanakan di Pegunungan Kulonprogo, Daerah Istimewa Yogyakarta, bertujuan untuk: (1) mengetahui karakteristik bentuklahan kejadian longsorlahan di daerah penelitian; (2) menganalisis secara komprehensif antara bentuklahan dan tanah dengan kejadian longsorlahan di daerah penelitian; dan (3) menyusun tipologi pedogeomorfik wilayah rawan longsorlahan di daerah penelitian berdasarkan karakteristik bentuklahan dan tanahnya. Metode yang digunakan dalam penelitian ini adalah metode surve i, perolehan data secara sampling dengan analisis gabungan kualitatif dan kuantitatif. Kejadian longsorlahan yang ada dikaji secara geomorfik dan pedologis untuk mengetahui tipologi pedogeomorfik kejadian longsorlahan mendatang. Cara pengambilan sampel dilakukan secara purposive (purposive sampling ). Variabel yang diamati, diukur, dan dikaji dalam penelitian ini meliputi variabel geomorfik (bentuklahan) , variabel antrophogenik, dan variabel pedologis (perkembangan tanah) yang menjadi faktor kejadian longsorlahan. Hasil penelitian menunjukkan bahwa karakteristik bentuklahan pada kejadian longsorlahan di Pegunungan Kulonprogo dikelompokkan menjadi enam kelompok, yaitu Perbukitan Denudasional, Lereng Atas Perbukitan Denudasional, Lerengkaki Perbukitan Denudasional, Perbukitan Perbukitan Struktural, Lereng Atas Perbukitan Struktural, dan Lereng Kaki Perbukitan Struktural. Tingkat perkembangan tanah awal (initial), sedang (juvenile ), dan lanjut (senile) yang dikelompokkan menjadi tiga jenis tanah (great group soil): Troportents, Eutropepts, dan Hapludalfs. Tingkat kerawanan longsorlahan dikelompokkan menjadi 3, yaitu rendah, sedang, dan tinggi. Tipologi pedogeomorfik kejadian longsorlahan di daerah penelitian dikelompokkan menjadi tujuh tipologi, yaitu: Perbukitan Denudasional Troporthent dengan tingkat kerawanan longsorlahan sedang, Perbukitan Denudasional Hapludalf dengan tingkat kerawanan longsorlahan sedang, Lereng Atas Perbukitan Denudasional Eutropept dengan tingkat kerawanan longsorlahan tinggi, Lereng Kaki Perbukitan Denudasional Troportent dengan tingkat kerawanan longsorlahan rendah, Perbukitan Struktural Troporthent dengan tingkat kerawanan longsor sedang, Lereng Atas Perbukitan Struktural Eutropept dengan tingkat kerawanan longsorlahan tinggi, Lereng Kaki Perbukitan Struktural Eutropept dengan tingkat kerawanan longsorlahan ringan.

This research dissertation at Kulonprogo Mountains aims to: (1) determine the landforms characteristic of landslide occurrence in research areas; (2) comprehensively analyze between landforms and soils with reference to landslide occurrence in research area; (3) construct pedogeomorphic typology in landslide prone areas in this research area based on the characteristic of landforms and soils. The method used in this study is a survey method, data acquistion was done by taking a sample which is then examined with the qualitative and quantitative analysis. The existing landslide occurrence was studied by geomorphic and pedology approach to determine the pedogeomorphic typology of future landslide occurrence. Purposive sampling was conducted in this research. And then do the measurement and assessment to the observed variables. In this research, geomorphic variable (landform), antrophogenic variable, and pedology variable (soil development) is a major factor in landslides occurrence. The results showed that the characteristic of landforms in the occurrence landslide at Kulonprogo mountains could grouped into six groups , namely: (1) denudasional hills, (2) the upper slopes of denudasional hills, (3) the footslopes of denudasional hills, (4) the structural hills, (5) the upper slope of structural hills, and (6) the footslopes of structural hills. The level of soil development of initial (initial), intermediate (juvenile), and advanced (senile) stage can grouped into three major/ great group, namely: troporthents, eutropepts, and hapludalfs. Vulnerability of landslide can be group into three groups , namely: low, medium, and high. The typology of pedogeomorphic landslide occurrence in the research area can be grouped into seven typologies, namely: (1) the troporthents denudasional hills with moderate level of vulnerability to landslide, (2) the hapludalfs denudasional hills with moderate level of vulnerability to landslide, (3) the upper slopes of eutropepts denudasional hills with high levels of vulnerability to landslide, (4) the footslopes of troporthents denudasional hills with low levels of vulnerability to landslide, (5) the structural troporthents denudasional hills with moderate level of vulnerability to landslide, (6) the upper slopes structural eutropepts hills with high level of vulnerability to landslide, and (7) the foot slopes structural eutropepts low levels of vulnerability to landslide.

Kata Kunci : tipologi pedogeomorfik, longsorlahan, dan perbukitan/pegunungan