Landslide hazard zonation using logistic regression technique: the case of Shafe and Baso catchments, Gamo highland, Ethiopia

Landslide hazard zonation plays an important role in safe and viable infrastructure development, urbanization, land use, and environmental planning. The Shafe and Baso catchments are found in the Gamo highland which has been highly degraded by erosion and landslides thereby affecting the lives of the local people. In recent decades, recurrent landslide incidences were frequently occurring in this Highland region of Ethiopia in almost every rainy season. This demands landslide hazard zonation in the study area in order to alleviate the problems associated with these landslides. The main objectives of this study are to identify the spatiotemporal landslide distribution of the area; evaluate the landslide influencing factors and prepare the landslide hazard map. In the present study, lithology, groundwater conditions, distance to faults, morphometric factors (slope, aspect and curvature), and land use/land cover were considered as landslide predisposing/influencing factors while precipitation was a triggering factor. All these factor maps and landslide inventory maps were integrated using ArcGIS 10.4 environment. For data analysis, the principle of logistic regression was applied in a statistical package for social sciences (SPSS). The result from this statistical analysis showed that the landslide influencing factors like distance to fault, distance to stream, groundwater zones, lithological units and aspect have revealed the highest contribution to landslide occurrence as they showed greater than a unit odds ratio. The resulting landslide hazard map was divided into five classes: very low (13.48%), low (28.67%), moderate (31.62%), high (18%), and very high (8.2%) hazard zones which was then validated using the goodness of fit techniques and receiver operating characteristic curve (ROC) with an accuracy of 85.4. The high and very high landslide hazard zones should be avoided from further infrastructure and settlement planning unless proper and cost-effective landslide mitigation measures are implemented.

LANDSLIDE HAZARD ASSESSMENT APPROACH ON THE PROVINCIAL ROAD IN EAST JAVA

Landslide hazard mapping on the road infrastructure has 2 (two) main sources. The first is through a landslide inventory survey, and the second is through recording data on past landslide events. Each of the methods above has advantages and disadvantages. The most appropriate moment in making a landslide hazard map is when a certain disaster strikes an area with a certain measured impact. The Unpredictable variables that have been hidden and difficult to predict will be eliminated. Disaster events in disaster-prone mapping become a key variable as well as a validator. The characteristic of the landslide on road is also very specific, depends on the nature of the vehicle's spatial movement, and the scope of the affected area which is narrow but extends along the slopes coincide with the road. The most appropriate disaster mapping in measuring the level of hazard, vulnerability, and risk on the road is based on landslide record data. That is because the variables used to predict landslide events are extremely varied and too many are unknown. Assessing a map using a landslide disaster occurrence on the road is easier than making a map through the calculation method of certain variables that are overlapped. Based on the calculation of frequency analysis for 12 years, the daily rainfall value of 126.2 mm per day is the threshold of rain which has a probability of a landslide of 95% on the road infrastructure in East Java Province.

Inventory of landslides triggered by hurricane Matthew in Guantánamo, Cuba

An inventory of landslides triggered by Hurricane Matthew (4–5 October 2016) through the eastern region of Cuba was carried out using Sentinel 2A satellite images. The inventory was compared with the slope map generated from the digital elevation model at 25 m per pixel and with the geological map at 1: 100 000 scale. The precipitation data from the 1-hour rain gauge records of four stations of the Cuban Institute of Meteorology (INSMET) and 24-hour rain gauge records of six stations of National Institute of Hydraulic Resources (INRH) were processed and analysed during this event. In total, 237 landslides were classified into rockslides, debrisflows and topples. A wide distribution of landslides was found within the selected slope classes, depending of the landslide type. Most of the landslides were generated in green schist of volcanic and vulcanoclastic rocks and rocks of the ophiolitic complex made up of ancient remains of oceanic crust. Findings increase understanding of landslide occurrence in this area in order to update landslide hazard map and to reduce landslide risk.

Identifikasi Rawan Bencana Tanah Longsor Kabupaten Toraja Utara

North Toraja Regency is an area that is prone to landslides with a potential zone of medium to high ground movement, which has resulted in damage to land transportation routes between districts being cut off, damage to buildings, and loss of lives. The focus of this research is to determine the level of vulnerability and map the class of landslide hazards in the North Toraja Regency. This type of research is descriptive qualitative with Geographical Information Systems (GIS) approach and then analyzed by overlay and scoring (weighting). Based on data processing, the study produced a landslide hazard map in North Toraja Regency with five classes of vulnerability, namely: very low area of 58,049 km2 (50%), low area of 118,087 km2 (11.18%), medium area of 256,057 km2 (22.07%), rather high area of 195,872 km2 (16.07%), very high area of 11,972 km2 (1.03 %).

Spatial Landslide Risk Assessment at Phuentsholing, Bhutan

Landslides are one of the most destructive and most recurring natural calamities in the Himalayan region. Their occurrence leads to immense damage to infrastructure and loss of land, human lives, and livestock. One of the most affected regions is the Bhutan Himalayas, where the majority of the landslides are rainfall-induced. The present study aims to determine the hazard and risk associated with rainfall-induced landslides for the Phuentsholing region located in the southwestern part of the Bhutan Himalayas. The work involves developing a landslide risk map using hazard and vulnerability maps utilizing landslide records from 2004 to 2014. The landslide hazard map was generated by determining spatial and temporal probabilities for the study region. The spatial probability was computed by analyzing the landslide contributing factors like geology, slope, elevation, rainfall, and vegetation based on comprehensive field study and expertise about the area. The contributing factors were divided into various classes and the percentage of landslide occurrence under each class was calculated to understand its contributing significance. Thereafter, a weighted linear combination approach was used in a GIS environment to develop the spatial probability map which was multiplied with temporal probabilities based on regional rainfall thresholds already determined for the region. Consequently, vulnerability assessment was conducted using key elements at risk (population, land use/land cover, proximity to road, proximity to stream) and the weights were provided based on expert judgment and comprehensive field study. Finally, risk was determined and the various regions in the study area were categorized as high, medium, and low risk. Such a study is necessary for low-economic countries like Bhutan which suffers from unavailability of extensive data and research. The study is conducted for a specific region but can be extended to other areas around the investigated area. The tool can serve as an indicator for the civil authorities to analyze the risk posed by landslides due to the rapid infrastructure development in the region.

Evaluation of landslide hazard and its impacts on hilly environment of the Nilgiris District - a geospatial approach

Landslide Hazard Zonation (LSH) maps play a key role in landuse planning particularly in landslide prone areas. LSH mapping is globally accepted one for analyzing the area for landslide susceptibility. Different approaches were followed by many researchers in India to prepare landslide hazard zonation mapping depending upon their need and requirement. The Nilgiris district in Western Ghats of India is one of the severe to high landslide hazard prone areas of India. Many agencies have carried out research on LSH mapping for the Nilgiris district with different scales. A systematic study of inventory and zonation was 122carried out in 1980’s by government agencies. However there is no proper updation or documentation on landslides after 1980’s in the district The purpose of this paper is to review the existing landslide-related studies in the district of The Nilgiris and review the district’s existing landslide hazard map with updated information. Landslide hazard maps in The Nilgiris were compiled in the GIS platform from various authenticated sources. Data on landslides from 1824 to 2014 were collected and a spatial database on landslides was created. A detailed inventory was analyzed and used for revision of the district’s landslide hazard impact on the 2009 landslides.. Based on the landslide inventory and densely populated areas and repeated landslides at the same locations, the most landslide hazard areas were identified.

Analysis of landslide hazard mapping of penang island malaysia using bivariate statistical methods

Landslide is one of the disasters which cause property damages, infrastructure destruction, injury and death. This paper presents the analysis of landslide hazard mapping of Penang Island Malaysia using bivariate statistical methods. Bivariate statistical methods are simple approach which are capable to produce good results in short computational time. In this study, three bivariate statistical methods, i.e. Frequency Ratio (FR), Information Value (IV) and Modified Information Value (MIV) are used to generate the landslide hazard maps of Penang Island. These bivariate statistical methods are computed using MATLAB tool. Landslide hazard map is categorized into 4 levels of hazard. The accuracy of each method and effectiveness in predicating landslides are validated and determined by using Receiver of Characteristics curve. The accuracies of FR, IV and MIV methods are 79.58%, 79.14% and 79.37% respectively.

An approach of preparing earthquake induced landslide hazard map: a case study of Nuwakot District, central Nepal

The Gorkha Earthquake-2015 triggered landslides which are widespread in central Nepal. The landslides swept away physical infrastructures like roads, schools, public and residential buildings, and cultivated lands at several locations. This indicated that the decision makers were not aware of the fact that the locations for possible earthquake-induced landslides can be predicted, and physical infrastructure development can be planned accordingly. What is needed for the purpose is an earthquake-induced landslide hazard map which is a useful tool in decision making, particularly for finding safer geographical locations for residential and public building construction, and also for other physical infrastructure development. Immediately after the Gorkha Earthquake-2015, JICA prepared an earthquake-induced landslide hazard map of the Gorkha and the Sindhupalchowak Districts using a certain methodology. But there remains a research question regarding whether the same methodology can be applied in preparing earthquake-induced landslide hazard maps of other earthquake-affected districts located away from the epicenter area. The main purpose of this research was to apply the JICA methodology to prepare an earthquake-induced landslide hazard map of the Nuwakot District, central Nepal which is the one if the most affected district by Gorkha earthquake 2015. The second purpose was to examine whether the map captured the ground reality or not. While preparing the input data required, four major disaster factors were taken into consideration which includes, among others, slope inclination, slope direction, relationship with the major thrust and distance from the epicenter. These factors were classified and characterized according to their nature and condition. The result was then analyzed by using quantification theory. An earthquake-induced landslide hazard map was then prepared using QGIS as a major software tool. The map was also verified through ground-truthing visiting several locations of the study site. The proposed methodology can be used to prepare similar maps in other affected districts of Gorkha earthquake 2015, and suitable sites for constructing physical infrastructures like roads, residential and public buildings can also be identified using the maps.

KAJIAN PETA BAHAYA TANAH LONGSOR DI KABUPATEN BANGGAI LAUT, PROVINSI SULAWESI TENGAH (STUDY OF LANDSLIDE HAZARD MAP IN THE BANGGAI LAUT DISTRICT, CENTRAL SULAWESI PROVINCE)

ABSTRACTBanggai Laut District which consists of islands has many threats to natural disaster, one of them is landslide hazard. The landslides hazard in Banggai Laut District is formed due to morphology which mostly in the form of wavy morphology up to the hills. The thematic map data used in landslide hazard map analysis is the official data held by the Banggai Laut District Government. The weighting and rating system is carried out on several parameters: geology (15%), slope (40%), land cover (25%) and rainfall (20%). Data from these parameters are overlaid with geographic information system (GIS) to obtain the classification of landslide hazard maps, ie: high landslide hazard zones, moderate landslide hazard zones and low landslide hazard zones. High landslide hazard zones are evenly spread over 4 large islands, namely Banggai Island, Bangkurung Island, Labobo Island and Bokan Kepulauan Islands. The potential for high landslide hazard will become bigger with added disturbance of human activities. To smooth the development process in integrated Banggai Laut District, landslide hazard maps and other hazard maps are very necessary. The limited availability of data and information on the disaster in Banggai Laut District, the creation of landslide hazard map is very important as one of the parts to complement the data. With the establishment of Regional Disaster Management Agency (BPBD) of Banggai Laut District, disaster risk reduction is expected to be implemented more focused, integrated, comprehensive and well coordinated with related institutions. Keywords: Landslides, Hazard Maps, Banggai Laut, Disaster Risk Reduction, Focused and Integrated Development. ABSTRAKKabupaten Banggai Laut yang terdiri dari kepulauan mempunyai banyak ancaman terhadap bencana alam, salah satunya adalah bencana tanah longsor (gerakan tanah). Bahaya tanah longsor di Kabupaten Banggai Laut terbentuk akibat morfofologi yang sebagian besar berupa morfologi bergelombang sampai perbukitan. Data peta tematik yang digunakan dalam analisis peta bahaya tanah longsor adalah data resmi yang dimiliki oleh Pemerintah Kabupaten Banggai Laut. Sistem pembobotan dan penilaian dilakukan pada beberapa parameter yaitu: geologi (15%), lereng (40%), tutupan lahan (25%) dan curah hujan (20%). Data dari parameter-parameter tersebut dioverlay dengan sistem informasi geografi untuk mendapatkan klasifikasi peta bahaya tanah longsor, yaitu: zona bahaya tanah longsor tinggi, zona bahaya tanah longsor sedang dan zona bahaya tanah longsor rendah. Zona bahaya tanah longsor tinggi merata tersebar di 4 pulau besar, yaitu Pulau Banggai, Pulau Bangkurung, Pulau Labobo dan Bokan Kepulauan. Potensi bahaya longsor tinggi tersebut akan menjadi semakin besar dengan tambahan gangguan aktivitas manusia. Untuk kelancaran proses pembangunan secara terpadu di Kabupaten Banggai Laut, peta bahaya longsor dan peta-peta bahaya lainnya sangat diperlukan. Ketersediaan data dan informasi tentang kebencanaan yang masih terbatas di Kabupaten Banggai Laut, maka pembuatan peta kawasan rawan bahaya tanah longsor sangat penting sebagai salah satu bagian untuk melengkapi data tersebut. Dengan terbentuknya BPBD Kabupaten Banggai Laut, maka pengurangan risiko bencana diharapkan dapat dilaksanakan dengan lebih terarah, terpadu, menyeluruh serta terkoordinasi dengan baik dengan instansi terkait. Kata kunci: Tanah Longsor, Peta Bahaya, Banggai Laut, Pengurangan Risiko Bencana, Pembangunan Terarah dan Terpadu.

Dendrochronological dating as the basis for developing a landslide hazard map – An example from the Western Carpathians, Poland

Most landslide hazard maps are developed on the basis of an area’s susceptibility to a landslide occurrence, but dendrochronological techniques allows one to develop maps based on past landslide activity. The aim of the study was to use dendrochronological techniques to develop a landslide hazard map for a large area, covering 3.75 km2. We collected cores from 131 trees growing on 46 sampling sites, measured tree-ring width, and dated growth eccentricity events (which occur when tree rings of different widths are formed on opposite sides of a trunk), recording the landslide events which had occurred over the previous several dozen years. Then, the number of landslide events per decade was calculated at every sampling site. We interpolated the values obtained, added layers with houses and roads, and developed a landslide hazard map. The map highlights areas which are potentially safe for existing buildings, roads and future development. The main advantage of a landslide hazard map developed on the basis of dendrochronological data is the possibility of acquiring long series of data on landslide activity over large areas at a relatively low cost. The main disadvantage is that the results obtained relate to the measurement of anatomical changes and the macroscopic characteristics of the ring structure occurring in the wood of tilted trees, and these factors merely provide indirect information about the time of the landslide event occurrence.