Landslide hazard map: tool for optimization of low-cost mitigation

Abstract

Background: Landslide hazard mapping is a fundamental tool for disaster management activities in fragile mountainous terrains. The main purpose of this study is to carry out landslide hazard assessment by weights-ofevidence modelling and prepare optimized mitigation map in the Higher Himalaya of Nepal. The modelling was performed within a geographical information system (GIS), to derive a landslide hazard map of the North-West marginal hills of the Achham. Thematic maps representing various factors that are related to landslide activity were generated using field data and GIS techniques. Landslide events of the old landslides were used to assess the Bayesian probability of landslides in each cell unit with respect to the causative factors. Results: The analysis suggests that geomorphological and human-related factors play significant roles in determining the probability value. The hazard map prepared with five hazard classes viz. Very high, High, Moderate, Low and Very Low was used to determine the location of prime causative factors responsible for instability. Spatial distribution of causative factor was correlated with the mechanism and scale of failure. For the mitigation of such shallow-seated failure, bioengineering techniques (i.e. grass plantation, shrubs plantation, tree plantation along with small scale civil engineering structures) are taken as cost-effective and sustainable measures for the least developed country like Nepal. Based on prime causitive factors and required bioengineering techniques for stabilization of unstable road side slopes, mitigation map is prepared having 14 classes of mitigation measures. Conclusion: The mitigation map reveled only 6.8% road side slopes require retaining structures however that more than half of the instable slope can be treated with simple vegetative techniques. Therefore, high hazard doensnot demand expensive structures to mitigate it in each every case.

Use of Very High-Resolution Optical Data for Landslide Mapping and Susceptibility Analysis along the Karnali Highway, Nepal

“…Thus, it cannot be used for land-use planning, emergency response and engineering decisions directly. It can be used to provide a general overview of landslide hazard in the area and to delineate areas that might benefit from low-cost slope stabilization measures such as bioengineering [111,112]. These preventive measures not only help minimize landslide occurrence but also protect the population from its cascading impacts.…”

Penerapan Sistem Informasi Geografis Untuk Mengidentifikasi Tingkat Bahaya Longsor Di Kec. Sabbang, Kab. Luwu Utara, Prov. Sulawesi Selatan

“…Menggunakan SIG untuk menganalisis tanah longsor tergantung pada jenis longsornya (Yamagishi, 2017). Peta daerah rawan bencana longsor merupakan upaya untuk menyiapkan mitigasi bencana longsor (Dahal dan Dahal, 2017). Oleh sebeb itu penulis melakukan penelitian penerapan sistem informasi geografis untuk mengidentifikasi tingkat bahaya longsor di daerah Kec.…”

“…Variabel yang digunakan adalah variable kombinasi MAFF-Japan dalam Hermon, 2015; Nasiah dan Invanni, 2014. Tingkat bahaya longsor dihitung dengan menggunakan rumus berikut ini: Jenis tanah juga merupakan hal yang dapat memicu terjadinya longsor (Dahal dan Dahal, 2017). Daerah Kecamatan Sabbang, jenis tanah terdiri dari tanah podzols, lhitosols, regosols dan vertizol.…”

Valuing Green Infrastructure

“…For interventions aimed at preventing or mitigating the risk of landslides, this study uses data reported by Dahal and Dahal (2017). From the methods reported therein, we focus on two types: tree and bamboo plantation, and installation of subsoil drains.…”