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Landslides have been widely studied by geologists. However, previous studies mainly focused on the formation of landslides and never considered the effect of landslides on the structural characteristics of land-cover. Here we define the modeling of the graph topology for the land-cover, using the satellite images of the earth’s surface before and after the earthquake. We find that the land-cover network satisfies the power-law distribution, whether the land-cover contains landslides or not. However, landslides may change some parameters or measures of the structural characteristics of land-cover. The results show that the linear coefficient, modularity and area distribution are all changed after the occurence of landslides, which means the structural characteristics of the land-cover are changed.

Investigations of land management impacts on hydrology are well developed in South-East Asia, having been greatly extended by national organizations in the last two decades. Regional collaborative efforts, such as the ASEAN–US watershed programme, have helped develop skills and long-running monitoring programmes. Work in different countries is significant for particular aspects: the powerful effects of both cyclones and landsliding in Taiwan, the significance of lahars in Java, of small-scale agriculture in Thailand and plantation establishment in Malaysia. Different aid programmes have contributed specialist knowledge such as British work on reservoir sedimentation, Dutch, Swedish and British work on softwood plantations and US work in hill-tribe agriculture. Much has been achieved through individual university research projects, including PhD and MSc theses. The net result is that for most countries there is now good information on changes in the rainfall–run-off relationship due to forest disturbance or conversion, some information on the impacts on sediment delivery and erosion of hillslopes, but relatively little about the dynamics and magnitude of nutrient losses. Improvements have been made in the ability to model the consequences of forest conversion and of selective logging and exciting prospects exist for the development of better predictions of transfer of water from the hillslopes to the stream channels using techniques such as multilevel modelling. Understanding of the processes involved has advanced through the detailed monitoring made possible at permanent field stations such as that at Danum Valley, Sabah.

Ten years' hydrological investigations at Danum have provided strong evidence of the effects of extremes of drought, as in the April 1992 El Niño southern oscillation event, and flood, as in January 1996. The 1.5 km² undisturbed forest control catchment experienced a complete drying out of the stream for the whole 1.5 km of defined channel above the gauging station in 1992, but concentrated surface flow along every declivity from within a few metres of the catchment divide after the exceptional rains of 19 January 1996. Under these natural conditions, erosion is episodic. Sediment is discharged in pulses caused by storm events, collapse of debris dams and occasional landslips. Disturbance by logging accentuates this irregular regime. In the first few months following disturbance, a wave of sediment is moved by each storm, but over subsequent years, rare events scour sediment from bare areas, gullies and channel deposits. The spatial distribution of sediment sources changes with time after logging, as bare areas on slopes are revegetated and small gullies are filled with debris. Extreme storm events, as in January 1996, cause logging roads to collapse, with landslides leading to surges of sediment into channels, reactivating the pulsed sediment delivery by every storm that happened immediately after logging. These effects are not dampened out with increasing catchment scale. Even the 721 km² Sungai Segama has a sediment yield regime dominated by extreme events, the sediment yield in that single day on 19 January 1996 exceeding the annual sediment load in several previous years. In a large disturbed catchment, such road failures and logging-activity-induced mass movements increase the mud and silt in floodwaters affecting settlements downstream. Management systems require long-term sediment reduction strategies. This implies careful road design and good water movement regulation and erosion control throughout the logging process.

Soil moisture variation is crucial for predicting rainfall-triggered landslides because it is directly related to slope stability. However, the observation data of soil moisture is lacking and the data quality was not good enough for use over a long period. Therefore, the Noah Land Surface Model (Noah LSM) is an excellent alternative to construct soil moisture data. This study aims to construct soil moisture data using the Noah LSM and hence establish Landslide Early Warning System (LEWS) criteria using the Bayesian approach with soil moisture and cumulative event rainfall data. Using the Noah LSM, we can simulate the same soil levels with soil moisture observation data and compare the simulated soil moisture data and observation data depending on the soil texture. The results show that soil moisture variation between the model and observation is similar, especially in the summer season of May–October. According to the Bayesian approach, the critical soil moisture and cumulative rainfall range are different between sandy loam and loam. Finally, we can check the skill scores of the warning level and severe warning level’s soil moisture and cumulative rainfall conditions. The skill scores of the warning level showed that 50 cm and 30 cm soil moisture are the most significant in loam and sandy loam, respectively. In the severe warning level, the skill score shows no considerable difference in any soil layers in loam, but 50 cm soil moisture has the largest Hanssen and Kuipers (HK) skill score in sandy loam. We propose considering the Land Surface Model for constructing a soil moisture data tool in the landslide community. There is potential to upgrade the model by considering slope gradient.

Every year flooding and landslides cause severe material damages and thousands of deaths and injuries. To reduce the risk, measures can be taken by applying different management strategies either by reducing the probability of the event or by reducing the potential consequences in case of an event. This chapter provides a systematic (step-by-step) guidance, a brief overview of landslide and flood risk management in general and a summary of an investigation of the present risk management situation in Sweden which has resulted in some general recommendations. Examples of general recommendations are to apply available knowledge, for example by learning from existing good examples and, when available, lessons learned and documentation of the rational argumentation made in the decision process. There is a request of checklists and guides that can be used in the current daily work among planners and risk managers. It is important with a broad basis for decisions, therefore integrated assessments and valuations are recommended for example by applying multi-criteria analysis methodology and involving relevant stakeholders in the process for example through well working networks. It is further important to counteract the current trend that more automatic monitoring results in less field monitoring and reduced local knowledge.

In this paper the triggering mechanics, the prevention and mitigation methods and the risk analysis of landslides are addressed. Two case histories are described. The first case history deals with the stabilization works of a landslide in Portugal. The anchored retaining walls founded on micropiles to stabilize the hills are described. The field and laboratory tests are referred, as well as the geological-geotechnical model. The design of the retaining walls was based in Eurocode 7 and in Eurocode 8. The results of anchorages tests and micropiles to calibrate the design values are presented.

The second case history is related with La Josefina site in Ecuador, where a huge failure has occurred with around 30 cubic millions of rock materials killing more than 100 persons. The canyon of the valley was blocked creating a lake with a volume of water higher than 200 cubic millions putting in great risk the cities of Cuenca and Azuogues.

Landslides represent one of the most destructive natural hazards and a major threat in most hillside development. Over the years, there are little or no concerns on the importance of human factors to be considered as one of the major causes of landslide. Human Reliability Analysis (HRA) which in turn has been applied for quite sometimes in other industry sector to assess the human factors contributing to a risk and identifying proper mitigation measures to reduce the risk can be proposed to adopt into the geotechnical risk assessment. The needs to focus on the aspect of human factors in geotechnical engineering is inevitably due to the facts that human interaction interrelated at all stages from planning to design, and construction to maintenance stages. This paper will review the current state of landslide, human factors and its influence in Malaysia, introduction of HRA and discusses on the second generation HRA method known as CREAM.