Zhouqu County Research Articles

Characterizing sudden geo-hazards in mountainous areas by D-InSAR with an enhancement of topographic error correction

Differential interferometric synthetic aperture radar (D-InSAR) has been viewed as a promising technique in monitoring sudden geo-hazards (e.g., earthquake and landslide) in mountainous areas. However, the tough natural settings (e.g., steep slopes and vegetation) pose the D-InSAR technique to face many challenges. Among them, phase residuals induced by inaccurate topographic heights that can result in intolerable error have not been paid adequate attention. We present, in this paper, a new strategy of using D-InSAR measurements to characterize sudden geo-hazards with an emphasis on the correction of topographic errors. In the proposed strategy, a least squares model with an outlier detector is constructed to estimate the topographic errors from multi-baseline wrapped differential interferograms, and the error-prone phase unwrapping procedure is not needed. The new strategy is applied to the ALOS PALSAR images acquired for monitoring a giant mudslide occurred in Zhouqu County, China. After refining the topographic height originally from the inaccurate ASTER GDEM, notable improvements to the D-InSAR measurements can be clearly seen, which is helpful to better interpret the deformation signals associated with the mudslide event. It is observed that the Zhouqu mudslide had caused large ground movements in the Luojiayu and Sanyanyu groove valleys. In addition, we find that the Suoertou landslide has been experiencing moderate ground movements during the geologic event.

Research on the Landslide Recognition Based on Remote Sensing

In order to analyze the spatial distribution of landslides and its characteristics about the surface condition of landslides, a typical large landslide called the Xieliupo located in Zhouqu County was choosed as an example, comparing the data obtained from the field investigation with the initiatory interpretation result using remote sensing images. The results show that the proposed typical interpretation signs for landslide recognition have been improved right and could produce obvious identification results which were consistent with visual interpretation. Since the above method has been confirmed practical in the landslide recognition, we finally apply the method and experience in interpretation of landslide based on RS to the recognition of other large landslides, which can provide the theoretical basis for the subsequent research of landslides.

Assessment of the Risk of Debris Flows in Zhouqu County, South Gansu Province, China

The hazards of debris flows and the vulnerability to these flows were used as a basis for risk assessment in Zhouqu County, southern Gansu Province, China. The GIS software was used to perform a regional risk assessment for each township in Zhouqu County with a 250 m×250 m spatial resolution. The vulnerability of the population, the economy, and the ecological environment were accounted to develop a comprehensive vulnerability index for each township. A risk assessment model was used to develop a risk zoning map for Zhouqu County. It is found that the areas with the highest risk were mainly distributed in Chengguan, Dongshan, Jiangpan, Dachuan, and Guoye townships. Based on the results of the study, the recommendations for disaster prevention and mitigation were proposed.

The devastating Zhouqu storm‐triggered debris flow of August 2010: Likely causes and possible trends in a future warming climate

AbstractOn 8 August 2010 in the northwestern Chinese province of Gansu, a rainstorm‐triggered debris flow devastated the small county of Zhouqu. A modeling study, using a new multiple‐phase scalable and extensible geofluid model, suggests that the cause is an intersection of several events. These were a heavy rainstorm, not necessarily the result of global warming, which triggered the landslide and followed a drought that created surface cracks and crevasses; the geology of the region, notably the loess covering heavily weathered surface rock; and the bedrock damage, that deepened the surface crevasses inflicted by the 7.9 magnitude Wenchuan earthquake of 12 May 2008. Deforestation and topsoil erosion were critical contributors to the massive size of the debris flow. The modeling results underscore the urgency for a high‐priority program of revegetation of Zhouqu County, without which the region will remain exposed to future disastrous, “progressive bulking” type landslides. Debris flows are more predictable types of landslides; consequently, a series of “pseudo climate change” model experiments of future extreme precipitation events are carried out using the Weather Research and Forecasting model, forced by temperature perturbations from an ensemble of climate models. In a possibly future warmer climate, extreme precipitation events are anticipated to be more severe, and this study has identified an atmospheric blocking pattern that might produce future extreme precipitation events in the peri‐Tibetan Plateau (TP) area (located to the northeast of the TP). Importantly, observations from gravity field measuring satellites indicate that the larger geological environment of this region also is becoming increasingly unstable.

Wild food plants used by the Tibetans of Gongba Valley (Zhouqu county, Gansu, China).

BackgroundThe ethnobotany of Tibetans is a seriously under-studied topic. The aim of the study was to investigate knowledge and use of wild food plants in a valley inhabited by Tibetans in the Gannan Tibetan Autonomous Region.MethodsThe field research was carried out in a wooded mountain valley in 9 neighbouring villages the Zhouqu (Brugchu) county, and comprised 17 interviews with single informants and 14 group interviews, involving 122 people altogether.ResultsWe recorded the use of 81 species of vascular plants from 41 families. Fruits formed the largest category, with 42 species, larger than the wild greens category, with 36 species. We also recorded the culinary use of 5 species of edible flowers, 7 species with underground edible organs and 5 taxa of fungi. On average, 16.2 edible taxa were listed per interview (median – 16). Green vegetables formed the largest category of wild foods (mean – 8.7 species, median – 9 species), but fruits were listed nearly as frequently (mean – 6.9, median – 6). Other categories were rarely mentioned: flowers (mean – 0.2, median – 0), underground edible parts (mean – 0.3, median – 0) and mushrooms (mean – 1.5, – median 1).Wild vegetables are usually boiled and/or fried and served as side-dishes (cai). They are often lacto-fermented. Wild fruits are mainly collected by children and eaten raw, they are not stored for further use. The most widely used wild vegetables are: Eleuterococcus spp., Pteridium aquilinum, Helwingia japonica, Aralia chinensis, Allium victorialis, Pteridium aquilinum, Ixeris chinensis, Thlaspi arvense and Chenopodium album. The culinary use of Caltha palustris as a green vegetable is very interesting. In its raw state, marsh marigold is a toxic plant, due to the presence of protoanemonin. In this area it is dried or lactofermented before use. The most commonly eaten fruits are: Pyrus xerophila, Prunus salicina, Berchemia sinica, Rubus spp. and Eleagnus umbellata.ConclusionsThe number of wild taxa eaten in the studied valley is relatively large compared to most studies from around the world. However, compared to the northern slope of the Qinling, in Shaanxi, the list is considerably shorter, in spite of the similar methodology applied and similar research effort involved.

Research of the Health Monitoring System Scheme for High Slope in Zhouqu

The target of this paper is to get proper information of deformation through monitor the health of a large-scale trial. The slope in the process of the governance and reinforced slope are designed in the test in Zhouqu County, Gansu Province. Through Health Monitoring Test to high slope, the teat is to master deformation and internal force changes of the supporting structure, meanwhile determine the trend of slope deformation. It is possible to send out the warning for slope stability. Through researching the program and analyzing the data of future monitoring, it provides a reliable basis of similar slope engineering for future.

Numerical Simulation of Flash Floods Routing Based on Improved Leap-Frog Method

in the 2-d numerical simulation of flash flood disaster, due to flood often occurred in the steep terrain and water flow rapidly changed, lead to that the calculated value is unstable and even the calculation diverge in the simulation. This paper presents a grid outflow correction method, which is based on the leap-frog finite difference format, through modifying the outflow rate of the grid circularly, to ensure the mass conservation in the whole process of computing. In the local dam bursting model, the simulated result comparison of the grid outflow correction method and the algorithm of implicit alternating direction on the mass conservation shows that, the new method can ensure the simulation accuracy and the numerical stability under the condition of steep terrain and moving boundary. According to the proposed method, the simulation analysis in the process of extreme flash flood disasters which happened in 2010 Zhouqu county in Gansu province was carried out. The comparison of simulation results and remote sensing estimation results shows that the deviation of the flood evolution time, speed and impact height are within 5%, and the consistency of evolution path is good, which verifies the validity of the algorithm.

Characteristics, causation, and rehabilitation of Zhouqu extraordinarily serious debris flows in 2010, China

In early morning of Aug 8th, 2010, the rain-triggered tremendous debris flows broke out simultaneously at the Sanyanyu ravine and Luojiayu ravine, which locate in the north part of Zhouqu County town. The debris flow is the most severe event of the same kind of disasters in the past sixty years in China, which caused great losses of people’s lives and properties. Based on field investigation, remote sensing image interpretation and analysis of local climatological data, the local topographical conditions, active tectonic movement, massive debris source and torrential rains were the main formation causes which induced the catastrophic debris flows. Moreover, detailed geological surveys were carried out following the disaster, the other geological potential hazard sites were found out, and the geological and seismic hazard assessment has been put into practice. At last, scientific and appropriate countermeasures have been suggested to prevent and mitigate the extraordinarily serious debris flow.

Lessons learned from protective measures associated with the 2010 Zhouqu debris flow disaster in China

On August 7 and 8, 2010, a catastrophic debris flow disaster occurred in Zhouqu County in northwestern China’s Gansu Province. The large-scale debris flow event destroyed more than 200 buildings, killing approximately 1,700 people. Field investigations showed that the debris flow disaster was not only a natural hazard but also anthropogenic. First, the partial implemented check dams had not formed an integral blocking system to resist large events. Second, poor-quality workmanship contributed to the breakage of check dams. Third, disorderly placement of houses and buildings on the fan structure rendered the cross-sectional area of drainage channel too small to accommodate such a large event. The lessons learned from these hazards may be valuable for improving protective measures against these types of very large debris flow events in northwestern China in the future.

Epidemiological survey of school-age children with low vision in Zhouqu County of Gannan Tibetan autonomous prefecture of Gansu province

Epidemiological survey of school-age children with low vision in Zhouqu County of Gannan Tibetan autonomous prefecture of Gansu province

The 2010 Zhouqu mudflow disaster: possible causes, human contributions, and lessons learned

On August 7, 2010, a giant mudflow occurred in Zhouqu County, in China’s Gansu Province. It killed at least 1,467 people and destroyed many buildings. The extensive damage resulted partially from the impact of the swift mudflow, and partially from subsequent flooding caused by damming of the Bailong River, creating a lake. The mudflow had both internal and external causes. We discuss these in detail from the perspective of their relationship to human activities, with the goal of helping to provide advance warning of such disasters in the future.

WHY WAS THE AUGUST 2010 ZHOUQU LANDSLIDE SO POWERFUL?

On August 8, 2010 in the northwestern Chinese province of Gansu, rainstorm-triggered debris flow devastated the small county of Zhouqu. A modeling study, using a new multiple-phase scalable and extensible geo-fluid model, suggests that the cause is the result of an intersection of several events. These were a heavy rainstorm, not necessarily the result of global warming, which triggered the landslide and followed a drought that created surface cracks and crevasses; the geology of the region, notably the loess covering heavily weathered surface rock; and the bedrock damage, which deepened the surface crevasses, inflicted by the 7.9 magnitude Wenchuan earthquake of May 12, 2008. Deforestation and topsoil erosion also contribute. The modeling results underscore the urgency for a high priority program of re-vegetation of Zhouqu county, without which the region will remain exposed to future disastrous, “progressive bulking” type landslides.

WHY WAS THE AUGUST 2010 ZHOUQU LANDSLIDE SO POWERFUL?

On August 8, 2010 in the northwestern Chinese province of Gansu, rainstorm-triggered debris flow devastated the small county of Zhouqu. A modeling study, using a new multiple-phase scalable and extensible geo-fluid model, suggests that the cause is the result of an intersection of several events. These were a heavy rainstorm, not necessarily the result of global warming, which triggered the landslide and followed a drought that created surface cracks and crevasses; the geology of the region, notably the loess covering heavily weathered surface rock; and the bedrock damage, which deepened the surface crevasses, inflicted by the 7.9 magnitude Wenchuan earthquake of May 12, 2008. Deforestation and topsoil erosion also contribute. The modeling results underscore the urgency for a high priority program of re-vegetation of Zhouqu county, without which the region will remain exposed to future disastrous, “progressive bulking” type landslides.

Triggering conditions and depositional characteristics of a disastrous debris flow event in Zhouqu city, Gansu Province, northwestern China

Abstract. On 7 August 2010, catastrophic debris flows were triggered by a rainstorm in the catchments of the Sanyanyu and Luojiayu torrents, Zhouqu County, Gansu Province northwestern China. These two debris flows originated shortly after a rainstorm with an intensity of 77.3 mm h−1 and transported a total volume of about 2.2 million m3, which was deposited on an existing debris fan and into a river. This catastrophic event killed 1765 people living on this densely urbanised fan. The poorly sorted sediment contains boulders up to 3–4 m in diameter. In this study, the geomorphological features of both debris flow catchment areas are analyzed based on the interpretation of high-resolution remote sensing imagery combined with field investigation. The characteristics of the triggering rainfall and the initiation of the debris flow occurrence are discussed. Using empirical equations, the peak velocities and discharges of the debris flows were estimated to be around 9.7 m s−1 and 1358 m3 s−1 for the Sanyanyu torrent and 11 m s−1 and 572 m3 s−1 for the Luojiayu torrent. The results of this study contribute to a better understanding of the conditions leading to catastrophic debris flow events.

An Analysis of Sustainable Development Based on a Comparison of the Pre- and Post-Disaster Biocapacity and Ecological Footprint in Zhouqu County,China

Zhouqu County is not only an impoverished area but also a poor environment region. Frequent occurrence of geological disasters in Zhouqu, which largely determines the quality of ecological environment, affects the regional sustainable development. In this paper, on a case study of Chengguan Town of Zhouqu, two TM images acquired in pre- (2008)and post-disaster(2010) were selected to conduct the research, using remote sensing and GIS spatial analysis techniques. The state of the ecological environment and sustainable development of the region were evaluated by using the ecological footprint methodology. The results show: Firstly, the biocapacity of built-up area and cropland are reduced by 318.50gha and 82.78gha after debris flow disaster respectively, followed by forest land, grazing ground, fishing ground and barren ground, which has played a serious impediment in economic development; Secondly, the ecological deficit reaches to -0.9245gha/per-cap before disaster, however, it reduces to -1.0691gha/per-cap after disaster. This indicates that Chengguan Town is not sustainable development, after sudden disaster, the situation of unsustainable development becomes more serious; Thirdly, it is found that debris flow and landslides are mainly not only in forest land and cropland, also areas containing many people and buildings, which shows geological disasters has played a significant impact on the socio-economic development. Finally, this article provides scientific references for the restoring of ecological environment as well as scientific disaster relief after the debris flow disaster. Therefore, strengthening management and mitigation techniques of disaster is benefit to humans and socio-economic sustainable development.

Landslide alarm

Just after midnight on 8 August, a massive landslide sent nearly 2 million cubic meters of rock and mud hurtling through several towns in Zhouqu County, China. The natural disaster killed more than 1500 people in the county, which sits in a valley between two mountains in Gansu Province. Three months later, more than 250 people were still unaccounted for. Though their breakthrough is too late for the Zhouqu disaster, researchers at Loughborough University, in England, reported in October that they have developed an electronic system that can warn of an impending landslide by picking up the telltale sounds of shifting earth.

Textual research of Wudu earthquake in 186 B.C. in Gansu Province, China and discussion on its causative structure

On the basis of the textual research on the historical earthquake data and the field investigation of Wudu earthquake occurred in 186 B.C., we suggest that the earthquake parameters drawn from the present earthquake catalogs are not definite and amendments should be made. The heavily-damaged area of this earthquake should be located between Jugan township of Wudu County and Pingding township of Zhouqu County. Its epicenter should be in the vicinity of Lianghekou in Wudu County with a magnitude of about 7∼7¼ and an intensity of about IX∼X. The major axis direction of the heavily-damaged area should be in the WNW direction that is approximately consistent with the strike of the middle-east segment of Diebu-Bailongjiang active fault zone, and the origin time should match up to that of the latest paleoearthquake event [before (83±46) B.C.] obtained by the trench investigation. Certain seismic rupture evidences are still preserved on this fault segment. Therefore, we propose on the basis of comprehensive analysis that the causative structure of the M 7∼7¼ Wudu earthquake in 186 B.C. should be in the middle-east segment of Diebu-Bailongjiang active fault zone.

Acceptable risk of environmental air pollution

Risk acceptability is an inevitable problem in human societies. In this case study of a debris-flow prone area in Zhouqu County of Gansu Province in northwestern China, on-site questionnaire surveys were administered and statistical analysis was conducted to evaluate public acceptance of debris-flow disasters and to identify the critical factors influencing their acceptability. The results indicate that local people's principal concern with regard to debris-flow-disaster consequences was disease occurrence, and their secondary concern was environmental destruction. Housing-related destruction represented the most common property-loss concern. The acceptability value of the distance between people's living or working place and debris-flow-disaster location (Distance) was 3.25 (moderate grade); the frequency of debris-flow occurrence in each community or village (Frequency) received an acceptability value of 1.43 (low grade); the warning time before debris-flow occurrence (Warning time) received an acceptability value of 3.18 (moderate grade); and people's willingness to pay for debris-flow-disaster insurance per year (Insurance premium) was reflected by an acceptability value of 3.33 (moderate grade). The significant factors affecting Distance acceptability were age, sex, and income; the significant factors affecting Frequency acceptability were sex, occupation, and income; the significant factors affecting Warning-time acceptability were educational level and income; and the significant factor influencing Insurance-premium acceptability was educational level. Income played the most influential role in respondents’ assessments of debris-flow-disaster acceptability. This study may provide insight into the reasons behind the courses of action people choose when faced with debris-flow disasters.