Lianyou Liu

China's Drought Disaster Risk Management: Perspective of Severe Droughts in 2009-2010

China has been frequently and heavily affected by drought disasters. During 2009–2010, three large-scale severe droughts struck China, caused considerable social, economic, and ecological losses. These droughts showed significant regional differences. This study employs a two-stage transition framework comprising “entry” and “exit” transitions to discuss disaster risk management of drought in China, by taking the three droughts as comparative case studies. Chinese society’s response in the exit transition is examined and the underlying factors that enable the entry trigger are diagnosed. The policy responses that lead to the exit transition from these drought disasters were appropriate, but there is substantial room for improvement in management strategy regarding both entry and exit transitions. This article suggests that government policies should emphasize entry-prevention measures that reduce adverse impacts early in a drought episode rather than focus solely on improving performance in achieving a rapid exit transition from drought.

Interaction among controlling factors for landslides triggered by the 2008 Wenchuan, China Mw 7.9 earthquake

The 12 May 2008 Mw 7.9 Wenchuan, China earthquake triggered about 200,000 landslides, which were controlled by a number of factors. This study examines five factors: slope angle, slope aspect, lithology, peak ground acceleration (PGA), and fault side (relative position on the seismogenic fault, i.e., hanging wall or footwall), to determine how these factors control the co-seismic landslide occurrence and whether one or more factors, acting alone or in concert, are involved in promoting or suppressing landslides. We performed a multi-factor statistical analysis using data from the 2008 Wenchuan earthquake. The results show that in the areas characterized by steep topography or where strong ground shaking occurred during the earthquake, there is a closer relationship between slope aspect and landslide number density (LND) than other areas. The relationship between lithology and LND values depends on PGA. In turn, the relationship between LND values and PGA is also influenced by lithology. In addition, the controlling effect of lithology on co-seismic landslides on the hanging wall of the seismogenic fault is greater than that on the footwall. Examining interactions among these factors can improve understanding of the mechanisms of co-seismic landslide occurrence.

Land degradation and blown-sand disaster in China

China is a country with severe land degradation and blown sand disasters. The arid and semi-arid regions, in which land desiccation, vegetation degeneration, wind erosion, sandification, Gobi-pebblization and salinization occur, take up one third of China’s total land area. Vegetation degradation is most serious in lower flood plains of the inland rivers and the semi-arid Agro-pastoral Ecotone due to excessive use of water resources, grassland reclamation, overgrazing and collection of firewood and herbal medicines. Wind erosion features are common around terminal dry lakes, in inland-river fluvial plains, and the semi-arid dry grasslands. Studies by the methods of aeolian sand transport, soil texture analysis, 137Cs tracing and archaeology confirmed that the rate of wind erosion is normally between 1000 to 2000 ton km−1 a−1. The gravel Gobi on Mongolian Plateau has been formed to a large degree by wind erosion. The severity of sandification has been manifested by the twelve sandy deserts and lands occupying 710, 000 km2, and the enlargement of sandy land at increasing spreading rates in the past three decades. Salinization has not received enough public attention yet, but soil salinization in Ningxia and Hetao Plains and dry lake basins is unfavorable for crop growth and natural vegetation. Salinization of surface water and ground water in the lower reaches of most inland rivers restricts utilization of insufficient water resources. The exacerbation of sand and dust storms disasters is the ultimate outcome of desertification in China.

East Asian dust storm in May 2017: observations, modelling and its influence on Asia-Pacific region

A severe dust storm event originated from the Gobi Desert in Central and East Asia during 2–7 May 2017. Based on Moderate Resolution Imaging Spectroradiometer (MODIS) satellite products, hourly environmental monitoring measurements from Chinese cities and East Asian meteorological observation stations, and numerical simulations, we analysed the spatial and temporal characteristics of this dust event as well as its associated impact on the AsiaPacific region. The maximum observed hourly PM10 (particulate matter with an aerodynamic diameter ≤ 10 μm) concentration was above 1000 μg m−3 in Beijing, Tianjin, Shijiazhuang, Baoding, and Langfang and above 2000 μg m−3 in Erdos, Hohhot, Baotou, and Alxa in northern China. This dust event affected over 8.35 million km2, or 87 % of the Chinese mainland, and significantly deteriorated air quality in 316 cities of the 367 cities examined across China. The maximum surface wind speed during the dust storm was 23– 24 m s−1 in the Mongolian Gobi Desert and 20–22 m s−1 in central Inner Mongolia, indicating the potential source regions of this dust event. Lidar-derived vertical dust profiles in Beijing, Seoul, and Tokyo indicated dust aerosols were uplifted to an altitude of 1.5–3.5 km, whereas simulations by the Weather Research and Forecasting with Chemistry (WRFChem) model indicated 20.4 and 5.3 Tg of aeolian dust being deposited respectively across continental Asia and the North Pacific Ocean. According to forward trajectory analysis by the FLEXible PARTicle dispersion (FLEXPART) model, the East Asian dust plume moved across the North Pacific within a week. Dust concentrations decreased from the East Asian continent across the Pacific Ocean from a magnitude of 103 to 10−5 μg m−3, while dust deposition intensity ranged from 104 to 10−1 mg m−2. This dust event was unusual due to its impact on continental China, the Korean Peninsula, Japan, and the North Pacific Ocean. Asian dust storms such as those observed in early May 2017 may lead to wider climate forcing on a global scale.

Soil Macropore Structure under Different Land Uses Characterized by X-ray Computed Tomography in the Qinghai Lake Watershed, NE Qinghai-Tibet Plateau

Abstract Quantification of soil macropore is important to enhance our understanding of preferential pathways for water, air, and chemical movement in soils. However, the soil architecture of different land uses is not well understood elusive in Alpine region. The objective of this study was to quantify the architecture of soils beneath Alpine Kobresia meadow, Farmland, and Sand using computed tomography in the Qinghai Lake Watershed of northeastern Qinghai-Tibet Plateau. Nine soil cores (0–50 cm deep) were taken at three sites with three replicates. At each site, the three cores taken were scanned with a GE HISPEED FX/I Medical Scanner. The number of macropores, macroporosity, and macropore equivalent diameter within the 50-cm soil profile were interpreted from X-ray computed tomography, to analyze soil architecture. The analysis of variance indicated that land use significantly influenced macroporosity, the mean macropore equivalent diameter, and the number of soil macropore. The results indicated that soils under Alpine Kobresia meadow and Farmland had greater macroporosity, and developed deeper and longer macropores than that under Sand. For the Alpine Kobresia meadow, macropores were distributed mainly in the 0–100-mm soil layer, while they were distributed in the 0–200-mm soil layer for Farmland. The large number of macropores found in soil under Alpine Kobresia meadows and Farmland can be attributed to greater root development. The results from this study provide improved quantitative evaluation of a suite of soil macropore features that have significant implications for non-equilibrium flow prediction and chemical transport modeling in soils.

Desertification and Blown Sand Disaster in China

Approximately 331 million ha, one-third of China’s total land, is prone to desertification processes, leading to natural disasters and economic losses. In this study, the situation, tendency, their influences and their risk governance of desertification and blown sand disaster in China were examined using satellite images, field photographs, field data and a literature review. The desiccated areas in Lop Nor and the lower Heihe River fluvial plain covered about 50,000 km and 40,000 km, respectively. In Ejina, about 100 species of vegetation became extinct. The rate of wind erosion in China was between 1,000 tons/km/year and 2,000 tons/km/year. There were 12 sand deserts and sandy lands, occupying a total of 710,000 km. Salinized soils occurred across 99.1 million ha. The two main sand and dust storm-prone areas in China were the Tarim Basin and its surroundings, and the Alxa Plateau and its surroundings. From 1981 to 2007, the annual average frequency of sand and dust storms varied from 1 d to 37 d with a general increase from southeast to northwest. Since 1978, China has implemented a number of ecological construction projects that have reduced desertification from 1999 to 2004 and from 2005 to 2009, and the number of dust and sand storm days from 9.3 d between 1954 and 1959 to 4.4 d between 2000 and 2007. The results could improve understanding of desertification and blown sand disasters in China and provide valuable experiences for global desertification control.