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1.
This study discusses vegetation recovery and land cover change with reference to the Chiufenershan landslide, a major disaster caused by the Chichi earthquake, 21 September 1999. Image classification technology, landscape indicators from multi-temporal remotely sensed data and a field survey provide the data. Image differencing methods and threshold values coupled with pre- and post-quake satellite images were used. Multi-temporal images in combination with various vegetation indices were drawn on to classify land cover patterns and discuss differences and suitability of indices. Landscape indicators and field investigations fed into an investigation of vegetation recovery and landscape change. The study results show that the best image classification system is original wavebands coupled with a cropping management factor index (CMFI). The land cover analysis shows that areas of forest and grass are increasing and areas of landslide are decreasing. From the field investigation, because the left and right sides of the landslide area were not disturbed by the earthquake, their calculated similarity index is the highest (30.08%). Miscanthus floridulus is the most dominant pioneer plant at the landslide collapse area with an importance value index (IVI) of 63.6%.  相似文献   

2.
In this study, we tracked and analyzed the reconstruction process in Bam, Iran, after the city was struck by an earthquake with a M w of 6.6 on December 26, 2003. We adopted three approaches to comprehensively assess the city’s post-earthquake reconstruction and to shed light on the progress and sustainability of disaster recovery projects. We applied the following methodology. First, we obtained official statistics and reports that included quantitative and qualitative evaluations of the reconstruction process to evaluate the overall outcome of the government’s reconstruction projects. Second, we examined photographs taken during field surveys conducted in 2004, 2007, and 2014 to assess changes within the city. Last, we analyzed three satellite images of Bam—the first taken 3 months before the earthquake, the second immediately after the earthquake, and the third 8 years after the earthquake—to assess the progress of reconstruction work and changes in land cover and land use. The results indicated that considerable progress had been made in reconstructing some of the damaged areas. However, progress was relatively slow in severely damaged areas.  相似文献   

3.
The Ms8.0 Wenchuan earthquake that occurred on 12 May 2008 in southwestern China and triggered numerous landslides is one of the stronger ones in the steep eastern margins of the Tibetan Plateau. The surfaces of these landslides have recovered gradually with vegetation, which provide useful information about the evolution of geologic environment as well as the long-term assessment of landslides after earthquake. The Mianyuanhe watershed shows many co-seismic landslides. The active fault passing through its center is selected as a study area aiming to analyze the annual surface recovery rate (SRR) of landslides by interpretation of remote-sensing images in five periods from 2008 to 2013. The results are here described. (1) Although a large amount of loose deposits were transformed into debris flows, the surfaces of the landslides recovered rapidly with vegetation and almost no landslides occurred at new sites after the Wenchuan earthquake. In the year 2008, the exposed surface projected area (ESPA) of the landslides showed a total area of 56.3 km2 and covered 28.9 % of the study area, which was reduced rapidly to 19.1 % in 2011 and 15.8 % in 2013. (2) The study area was divided into four geologic units, including clastic rocks, melange zone, carbonate rocks, and magmatic rocks. Smaller ESPAs and higher SRRs were found in the former two units versus the latter ones. (3) A single large landslide shows an SRR lower than a group of smaller ones having an equal total surface, while the SRRs of debris flows are lower than those of rockfalls and landslides. (4) The vegetation cover would return to the pre-earthquake level in 2020 approximately, which indicates that the impact of the Wenchuan earthquake on landslides and debris-flows activities would cease almost completely.  相似文献   

4.
The Ms 8.0 Wenchuan earthquake in 2008 has led to huge damage to land surface vegetation in northwest Sichuan, one of the typical ecological fragile regions in China. In this paper, the vegetation degradation by the earthquake and its recovery after the disaster are evaluated from analysis of MODIS Gross Primary Productivity (GPP) time series products and other ancillary GIS data. The results suggest that local vegetation GPP after the earthquake in the heavy afflicted area has decreased by 22%. The local vegetation productivity in the heavy afflicted area had recovered to 84 and 87% after 1 and 2 months later. Since August 2008, the vegetation productivity has increased to a nearly normal level.  相似文献   

5.
2008年5月12日的汶川大地震引发了大规模同震山体滑坡，随后的强降雨又引发新的山体滑坡,滑坡形成的松散固体物质成为后续泥石流灾害的主要物质来源。为探究强震区泥石流流域崩滑体时空演变特征，文章以北川县魏家沟等8条泥石流流域为例，选取8期遥感影像（2008年震后、“9.24”泥石流发生后、2010年、2011年、2013年、2014年、2015年、2016年），分别解译崩滑体，统计其空间分布特征。此外，利用归一化植被指数（NDVI）计算研究区内植被覆盖度（VFC）及植被覆盖度恢复率（VCRR）。结果表明:研究区内崩滑体发育面积在强降雨作用后达到峰值，随后呈稳定恢复状态，面积逐年减小。崩滑体在高程900~1 100 m范围、坡度30°~45°范围、坡向90°~135°范围、距沟道150 m范围内发育面积最大。流域内植被覆盖度在2008年“9.24”泥石流灾害后最低，随后呈稳定恢复。自震后到2010年的时期内，植被覆盖度恢复率中等以下区域较多，植被恢复程度较低。2011年之后，流域内大多区域处于植被覆盖度恢复率中等以上等级，植被恢复程度较高。到2016年，研究区植被覆盖度已恢复至较高水平。研究表明:除地层岩性、微地貌等因素影响外，植被对泥石流活动性具有一定的抑制作用。  相似文献   

6.
The methodology for assessing the vegetation damaged by the Wenchuan earthquake by using the technologies of remote sensing and GIS was discussed in Dujiangyan city of Sichuan Province, China. The model of extracting vegetation from CBERS images was formulated using the differentiation knowledge of vegetation and non-vegetation discovered by image analysis and geographic analysis. The damage degree index (DDI) of the vegetation was defined here, which was the difference of the normalized difference vegetation index before the earthquake and that after earthquake. The China-Brazil Earth Resource Satellite (CBERS)-02’s images acquired, respectively, on 6 May and 27 June 2008, the model of extracting vegetation, and DDI were used to obtain the information about the area and degree of the damage vegetation in the study. There was 87.94 square kilometers vegetation damaged by Wenchuan earthquake, which accounted for 7.9% of the total area in Dujiangyan city. The area percentage of the damage vegetation in each grade related strongly and positively to the elevation grade and slope grade and weakly related to the aspect type. The distribution characteristics of the damage vegetation were useful for making plan of restoring vegetation here.  相似文献   

7.
The ecological water conveyance project that pipes water from Daxihaizi reservoir to lower reaches of Tarim River has been implemented ten times since 2000. After ecological water conveyance, restoration has taken place for vegetation along the dried-up lower reaches of the Tarim River. The changes of vegetation fluctuated yearly due to ecological water conveyance. In order to reveal the detailed process of vegetation changes, remote sensing images from 1999 to 2010 were all classified individually into vegetated and non-vegetated areas using the soil-adjusted vegetation index threshold method. Then inter-annual changes of vegetation over a period of 12 years were obtained using a post-classification change detection technique. Finally, spatial–temporal changes distribution of vegetation cover and its response to ecological water conveyance were analyzed. The results indicate: (1) vegetation area increased by 8.52 % overall after ecological water conveyance. Vegetation between 2003 and 2004 increased dramatically with 45.87 % while vegetation between 2002 and 2003 decreased dramatically with 17.83 %. (2) Vegetation area gain is greater than vegetation loss during 1999–2000, 2001–2002, 2003–2004 and 2009–2010 periods. Although vegetation restoration is obvious from 1999 to 2010, vegetation loss also existed except for the periods above. It indicates that vegetation restoration fluctuated due to ecological water conveyance. (3) Spatial distribution of vegetation restoration presented “strip” distribution along the river and group shaper in the lower terrain area, while spatial distribution of vegetation loss mainly located in the upper reaches of river and area far away from the river. (4) Vegetation restoration area had a positive relative with total ecological water conveyance volume. The scheme and season of ecological water conveyance had also influenced the vegetation restoration. The vegetation change process monitoring, based on continuous remote sensing data, can provide the spatial–temporal distribution of vegetation cover in a large-scale area and scientific evidences for implementing ecological water conveyance in the lower Tarim River.  相似文献   

8.
Understanding the ecological mechanisms and processes driving changes in our landscapes is significant for ecological conservation. This work used remote sensing with the extending contingency-based method to quantify the interchange relationship of land use types, and landscape metrics including spatially nuanced difference at patch level to track immigrants’ resettlement impacts at the semi-arid Hongsipu region with decadal agricultural pumping irrigation development in Ning Xia, China. Landsat-TM images acquired in 1989, 1999, 2003, and 2008 were used to study landscape changes in three periods, the earlier development from 1989 to 1999, the middle period in 1999–2003, and final stage in 2003–2008. The results showed the over 50 % landscape area experienced drastic change in each period with heavy immigrants’ perturbations since 1998. The nearly natural landscape with 1:1 area between desert and steppe in 1989 10 years before development, however, became the overwhelming barren landscape with almost 80 % of the study area in 2008, grassland and shrub land almost disappeared respectively, and cultivated land climbed to the third large type from about 2 % in 1989 to more than 16 % in 2008. The landscape became more fragmented, more regular shape with human disturbance spreading from the northwest low mountain and flat basin to the southeast diluvial fan, even high mountain at the end. Although Hongsipu pumping irrigation zone alleviates poor population pressure in the fragile ecological southern mountainous areas of Ningxia, the new artificial oasis creates another possible new ecological risk of the study area. Therefore, besides the economic development, the ecological conservation and restoration measures should be also the primary objectives in order to successful resettlement immigrants.  相似文献   

9.
The Wenchuan earthquake, also known as 2008 Sichuan Earthquake, occurred along the Longmenshan fault zone on 12 May 2008 at 14:28:01.42 CST (06:28:01.42 UTC). It caused serious damage to structures in the region. Beichuan is a town which is within these severely damaged areas. According to the earthquake intensity distribution map of 2008 Wenchuan earthquake officially released by the China Earthquake Administration, the earthquake intensity in Beichuan was XI on the China seismic intensity scale. As the earthquake occurred in a mountainous area, there were thousands of landslides, rockfalls, debris flows, and surface ruptures triggered by the earthquake over a broad area. These secondary geological hazards substantially increased the human, social and economic impact of the earthquake. This paper presents a post-earthquake analysis on the secondary geological hazards in Beichuan. The risk analyses associated with construction of the National Earthquake Memorial Museum in Beichuan are assessed and recommendations on risk mitigations for the mass reconstruction over the ruins are also provided based on this field study.  相似文献   

10.
During Typhoon Morakot which hit Taiwan from 6 to 9 August, 2009, Kaohsiung City was highly affected by devastating debris-flows and flooding. Recorded casualties were 699 deaths and 1,766 damaged homes, mostly in the mountainous areas of Kaohsiung City. Due to a largely malfunctioning or absent early-warning system, residents in those mountainous villages were required to rely on individual- and/or community-based capacities to evacuate and respond to debris-flow-related disasters. Hence, this study investigates the response behaviour of selected debris-flow-affected communities in Kaohsiung City, based on a preparedness awareness action and affect model. Key results from the survey highlight that only 13.8 % of the households received formal (institutional) early warning, whereas 86.2 % households had to rely on their intrinsic senses and indigenous knowledge to recognise the onset of debris-flows in their villages during Typhoon Morakot. Among those households who did not receive formal early warning, 10 % of the households received previous disaster education, 17 % had previous disaster experience, and 73 % did have neither disaster education nor disaster experience. Furthermore, households with disaster education were among those who were best prepared and knew best how to evacuate and respond to debris-flow-related disasters followed by households with disaster experiences. Finally, findings from the survey and selected key informants’ interviews identified that the response behaviour of communities ought to be enhanced through the following measures: conduction of hydro-meteorological-related disaster education, improved participatory risk communication and enhanced recognition of communities as vital actors during a disaster to provide local knowledge and support to relief operations.  相似文献   

11.
利用Landsat-8、高分1号、2号等卫星影像,评估九寨沟核心钙华景点及整个景区在“8·8”地震前、后和钙华生境保育修复后植被覆盖度、土壤湿度、森林面积和水系面积的动态变化。结果显示:人工为辅、自然为主的钙华保育修复后钙华核心景点和整个景区的高植被、中低植被、低植被覆盖面积均有了显著增加,裸地生态类型仍存在,但呈逐年减少趋势,中植被覆盖类型较震后和震前减少;保育后第二年,湿润和很湿润面积、总森林面积和水系面积比震前和震后都有大幅增加,高植被覆盖度面积、森林面积和水系面积间存在正相关关系,可能是由于人工干预下原生境快速恢复,提高了植被覆盖面积,植被的蒸散和截流作用进一步影响了流域的水文过程,促进了水系面积的恢复。   相似文献   

12.
Land cover and vegetation in Lake Baikal basin (LBB) are considered to be highly susceptible to climate change. However, there is less information on the change trends in both climate and land cover in LBB and thus less understanding of the watershed sensitivity and adaptability to climate change. Here we identified the spatial and temporal patterns of changes in climate (from 1979 to 2016), land cover, and vegetation (from 2000 to 2010) in the LBB. During the past 40 years, there was a little increase in precipitation while air temperature has increased by 1.4 °C. During the past 10 years, land cover has changed significantly. Herein grassland, water bodies, permanent snow, and ice decreased by 485.40 km2, 161.55 km2 and 2.83 km2, respectively. However, forest and wetland increased by 111.40 km2 and 202.90 km2, respectively. About 83.67 km2 area of water bodies has been converted into the wetland. Also, there was a significant change in Normalized Difference Vegetation Index (NDVI), the NDVI maximum value was 1 in 2000, decreased to 0.9 in 2010. Evidently, it was in the mountainous areas and in the river basin that the vegetation shifted. Our findings have implications for predicting the safety of water resources and water eco-environment in LBB under global change.  相似文献   

13.
Remote sensing is a cost-effective tool for assessing vegetation damage by typhoon events at various scales. Taking Xiamen Island, southeastern China, as a study case, this paper aimed to assess and analyze the vegetation damage caused by Typhoon Meranti landfalling on September 15, 2016, using two high spatial resolution remote sensing images before and after the typhoon event. Seven severely damaged vegetation regions were selected based on the classification of vegetation types and visual interpretation of the images. Regression analysis was used to correct seasonal variation of the two high-solution images before and after typhoon. The vegetation area of the whole of Xiamen Island and the selected seven regions before and after typhoon were then calculated, respectively. Two spectral vegetation indicators, normalized difference vegetation index (NDVI) and fractional vegetation coverage (FVC), were also retrieved for the whole island and the seven regions. By comparing the difference in NDVI values before and after the typhoon of the two high spatial resolution images, we analyzed the most affected vegetation areas, as well as the most seriously damaged vegetation species. The typhoon has caused a decrease in vegetation area by 95.1 ha across the whole Xiamen Island. The mean NDVI and FVC decreased by 0.209 and 13 percentage points, respectively. While, in the seven selected severely damaged areas, the mean NDVI decreased by 0.356–0.444 and FVC decreased by 27–42 percentage points. The visual inspection showed that the tone of typhoon-damaged vegetation became darker, the patches of damaged vegetation became smaller and more fragmented, and the gap between vegetation canopies became larger. The most affected vegetation areas occurred in the southeastern hilly area, Jinshang and Hubin South Roads, as well as the Wuyuan Bay area. The most seriously damaged vegetation type is broad-leaved trees, especially the species, Acacia confusa, Delonix regia, Bauhinia variegata, Chorisia speciosa, Ficus benjamina and F. Concinna.  相似文献   

14.
九寨沟7.0级地震诱发大量地质灾害对九寨沟景区景观、生态和基础设施造成了较大破坏，景区公路沿线灾害频繁，公路受损严重，多处中断，其中五花海与熊猫海之间的老虎嘴路段因地形地质条件极其复杂，受损最为严重。在九寨沟生态极其敏感区进行恢复重建等工程活动中，仅靠地灾评估无法满足工程方案评价的需要，同时须考虑工程活动、地灾和生态之间的相互影响。本文首次结合地灾风险评估，建立了生态敏感区的生态风险评估标准，在对九寨沟老虎嘴路段联合进行地灾评估和生态风险评估的基础上，对该路段道路恢复重建方案进行了评价论证，最终确定道路恢复重建方案。  相似文献   

15.
The 2008 Ms 8.0 Wenchuan earthquake triggered a large number of extensive landslides. It also affected geologic properties of the mountains such that large-scale landslides followed the earthquake, resulting in the formation of a disaster chain. On 10 July 2013, a catastrophic landslide–debris flow suddenly occurred in the Dujiangyan area of Sichuan Province in southeast China. This caused the deaths of 166 people and the burying or damage of 11 buildings along the runout path. The landslide involved the failure of ≈1.47 million m3, and the displaced material from the source area was ≈0.3 million m3. This landslide displayed shear failure at a high level under the effects of a rainstorm, which impacted and scraped an accumulated layer underneath and a heavily weathered rock layer during the release of potential and kinetic energies. The landslide body entrained a large volume of surface residual diluvial soil, and then moved downstream along a gully to produce a debris flow disaster. This was determined to be a typical landslide–debris flow disaster type. The runout of displaced material had a horizontal extent of 1200 m and a vertical extent of 400 m. This was equivalent to the angle of reach (fahrböschung angle) of 19° and covered an area of 0.2 km2. The background and motion of the landslide are described in this study. On the basis of the above analysis, dynamic simulation software (DAN3D) and rheological models were used to simulate the runout behavior of the displaced landslide materials in order to provide information for the hazard zonation of similar types of potential landslide–debris flows in southeast China following the Wenchuan earthquake. The simulation results of the Sanxicun landslide revealed that the frictional model had the best performance for the source area, while the Voellmy model was most suitable for the scraping and accumulation areas. The simulations estimated that the motion could last for ≈70 s, with a maximum speed of 47.7 m/s.  相似文献   

16.
Xiao  Yu  Olshansky  Robert  Zhang  Yang  Johnson  Laurie A.  Song  Yan 《Natural Hazards》2019,104(1):5-30

Catastrophic disasters can change the course of urban development and challenge the long-run sustainability of cities and regions. How to rapidly reconstruct communities impaired by catastrophic disaster is a world-wide challenge. The reconstruction after the 2008 Wenchuan earthquake in China was an unusual case of very rapid reconstruction after a catastrophic disaster. Over US$147 billion was invested to rebuild the damaged areas within 3 years. The reconstruction was not simply building back what was destroyed, but was used as an opportunity to advance national goals for urbanization, rural transformation, and poverty reduction. In this article, we review how the reconstruction was planned, budgeted, and financed in the sociopolitical context of 2008 China. Particularly, we discuss two innovative programs, namely pair assistance and land-based financing. Despite the unique circumstances of China, lessons can be learned to speed up post-disaster reconstruction and urban development in other countries. Conversely, this case illustrates that a narrow focus on physical reconstruction may overlook broader economic and social issues.

  相似文献   

17.
Soil erosion by water is recognised as a worldwide land degradation issue, particularly in arid and semi-arid regions. The aim of this study is to apply the powerful capabilities of advanced remote sensing and geographic information system techniques to identify the areas at risk to water erosion. This study presents the assessment of water erosion in mountainous areas (eastern Aures, Algeria) based on three main factors: the friability of the bedrock, degree of slope and density of vegetation cover. Alsat1 image was used to produce land use and vegetation (NDVI) maps. Digital elevation model was used in constructing the slope gradient map. The erosion risk map was obtained by the combination of indices assigned to thematic layers following multicriteria decision rules. Water erosion was generally not concerning in the eastern Aures (slight risk = 33 %, moderate risk = 44 % of the area). This simple–qualitative approach gave good results for assessing soil erosion equally to quantitative methods since 89.55 % of field verifications were accurate. The non-alarming state and the low rate of severe and extremely severe risk to erosion are due to (1) the low steep slopes, (2) the good quality of vegetation (forests with thick undergrowth), and which are occurring on (3) resistant materials of the substratum, and (4) the low human pressure. Results of this study, which may be conducted with reasonable costs and accuracy over large areas, are of significant help in prioritising areas in decision making and sustainable planning.  相似文献   

18.
Desertification is the major environmental threat in the arid and semiarid regions. The soil-adjusted vegetation index (SAVI) was used as an indicator to monitor the desertification change in Egypt. A multi-temporal satellite data of moderate-resolution imaging spectroradiometer were used to estimate SAVI and land surface temperature. Also, Global Multi-resolution Terrain Elevation Data 2010 and climatic data were used for the analysis. This research focuses on assessing the trend of the vegetation cover change in the seasons of January, March, June, September, and December for the years 2002, 2005, 2008, and 2011. The magnitude of the vegetation cover change in periods 2002–2005, 2005–2008, and 2008–2011 at ≤100 and >100 m elevation was analyzed. A major increase in the vegetation cover that occurred in the period 2002–2005 was about 3,400 km2, as a result of two national megaprojects (Toshka Project and El-Salam Canal). In contrast, vegetation cover decreased by 5,500 km2 in March during the period 2005–2008, coinciding with the period when the management of the megaprojects failed. Vegetation cover changed again by 1,500 km2 in the period of 2008–2011, and the vegetated areas in the Nile Delta were affected by the sea level rising which was responsible for the soil salinization. Three sites were chosen in this investigation (Kom Ombo, El-Oweinat, and Nile Delta) in order to observe the difference of desertification dynamics and to understand the relationship between the vegetation cover distribution and other environmental variables. Anti-desertification policies and advanced agricultural management are highly required in Egypt to decrease any environmental crises and food shortage.  相似文献   

19.
Spatial distributions of vegetation cover are closely related to topographical characters like slope, steepness, soil types, elevations, etc. In seismo-tectonic regions fault lines or tectonic lineaments are the most prominent surface signatures that can be reflected by vegetation distribution as tectonic displacement causes the change of topographical parameters. In the present study a part of northern Baromura hill (between 23º 42′ N to 23º49 N latitudes and 91º30 E to 91º36 E longitudes), which is considered as an active seismo-tectonic region of Tripura as well as northeast India, was selected for assessing the relationship between spatial variation of plant cover and topography. Geologically, Baromura hill is a north–south extended fold belt and formed by late Tertiary to Quaternary depositions. Evidences show that tectonic events played very important role in landform evolution of this area during the geological past. In this research an extensive fieldwork was conducted in the study area to understand the geomorphic and vegetation signatures and their environmental relationships. Various spectral resolutions of Landsat ETM+ were used for digital analysis. To analyse the vegetation character of this area digital operation was done within the spectral range 0.63–1.75 μm. Band 4 and band 3 were used for NDVI operation. Band 5 or mid-wave infrared band was classified in unsupervised mode to understand the range of plant water in the study area. Overlay operation with those operated images shows the spatial distribution pattern of vegetation cover indicates the landform condition. Three clear tectonic lineaments (faults) were detected from the digital study in on the northern part Baromura hill. Structural conditions of those fault lines were verified by geo-electrical survey during fieldwork. GPS tool was used for fixing the ground control points. Resistivity characters of the study area assessed from VES profile strongly supports that vegetation cover analysis from remotely sensed data within 0.63–1.75 μm spectral ranges can be a very useful tool for detecting surface tectonic signatures of the landform.  相似文献   

20.
To facilitate urban planning and management in fast-growing metropolitan areas, it is highly necessary to detect the spatiotemporal changes of different land cover types. This study aimed at identifying Beijing’s land cover types and detecting the characteristics of their spatiotemporal changes using time series remote sensing and GIS techniques from 1978 to 2010. A total of 16 Landsat MSS/TM/ETM+ images were collected during the spring and late summer seasons. After preprocessing the dataset, artificial neural network was used to perform the land cover classification. Consequently, four maps were generated for 1978, 1992, 2000, and 2010, with six classes (agriculture, woodland, grassland, water, urban, and barren land) according to the level I classification scheme. Three transition matrices were constructed to represent all possible changes that occur in the landscape. The results showed that agriculture, barren land, and grassland had an increase in area, while urban, water, and woodland had a reduction within the study area. A total of 2,032.341 km2 agriculture was reduced and 2,359.146 km2 woodland was increased. In the three periods for 1978–1992, 1992–2000, 2000–2010, agriculture had the largest amount of transfer out primarily to urban class around central urban areas and woodland had the most transfer in mainly from barren land in mountainous areas. More importantly, the driving forces analysis including economic development, growth of population and construction areas, and institutional policies was conducted to find out the primary factors inducing the land cover change.  相似文献   

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