2023 Vol. 50, No. 5
Article Contents

LIU Fan, DENG Yahong, MU Huandong, QIAN Faqiao. A study of the stability evaluation method of rainfall-induced shallow loess landslides based on the Maxent-Sinmap slope model[J]. Hydrogeology & Engineering Geology, 2023, 50(5): 146-158. doi: 10.16030/j.cnki.issn.1000-3665.202207050
Citation: LIU Fan, DENG Yahong, MU Huandong, QIAN Faqiao. A study of the stability evaluation method of rainfall-induced shallow loess landslides based on the Maxent-Sinmap slope model[J]. Hydrogeology & Engineering Geology, 2023, 50(5): 146-158. doi: 10.16030/j.cnki.issn.1000-3665.202207050

A study of the stability evaluation method of rainfall-induced shallow loess landslides based on the Maxent-Sinmap slope model

More Information
  • To address the problem of low evaluation accuracy of the Sinmap model in evaluating the stability of shallow loess landslides under the action of rainfall, a method based on the Maxent-Sinmap model is constructed to evaluate the stability of regional shallow rainfall loess landslides under the action of rainfall by improving the evaluation of the Sinmap model based on the maximum entropy model.Taking Zhidan County, Shaanxi Province, a high-incidence area of loess landslides, as an example, the relevant data of topography, geotechnical parameters and geological disasters were obtained by field and indoor work. The main environmental variables were obtained by Maxent model, and then the main environmental variables were partitioned. The Sinmap model was used to evaluate the stability of shallow loess landslides in different partitions under rainfall. The results show that based on the Maxent model, the landslide in Zhidan County is mainly affected by five indicators, such as slope, rainfall, landform, road buffer zone and normalized vegetation coverage index. The contribution rates to historical disaster points are 27.1 %, 20.3 %, 18.8 %, 18.7 % and 6.2 %, respectively. Compared with the traditional Sinmap model, the density of disaster points in the unstable area of the model increased by 17.26 %, 16.54 %, 17.39 %, 14.20 % and 12.96 % respectively under the conditions of light rainfall, moderate rainfall, heavy rainfall, rainstorm and downpour. The results of the Maxent-Sinmap model have a larger stable area than those of the Sinmap model, and there is no historical disaster distribution in the expanded area of the stable area. The model has higher accuracy and more reliable results, which can provide a better scientific basis for the evaluation of regional shallow rainfall landslides.

  • 加载中
  • [1] 刘东生,安芷生,文启忠,等. 中国黄土的地质环境[J]. 科学通报,1978,23(1):1 − 9. [LIU Dongsheng,AN Zhisheng,WEN Qizhong,et al. Geological environment of loess in China[J]. Chinese Science Bulletin,1978,23(1):1 − 9. (in Chinese) doi: 10.1360/csb1978-23-1-1

    CrossRef Google Scholar

    LIU Dongsheng, AN Zhisheng, WEN Qizhong, et al. Geological environment of loess in China[J]. Chinese Science Bulletin, 1978, 23(1): 1-9. (in Chinese) doi: 10.1360/csb1978-23-1-1

    CrossRef Google Scholar

    [2] 索安宁,李金朝,王天明,等. 黄土高原流域土地利用变化的水土流失效应[J]. 水利学报,2008,39(7):767 − 772. [SUO Anning,LI Jinchao,WANG Tianming,et al. Effects of land use changes on river basin soil and water loss in loess plateau[J]. Journal of Hydraulic Engineering,2008,39(7):767 − 772. (in Chinese with English abstract) doi: 10.13243/j.cnki.slxb.2008.07.019

    CrossRef Google Scholar

    SUO Anning, LI Jinchao, WANG Tianming, et al. Effects of land use changes on river basin soil and water loss in loess plateau[J]. Journal of Hydraulic Engineering, 2008, 39(7): 767-772. (in Chinese with English abstract) doi: 10.13243/j.cnki.slxb.2008.07.019

    CrossRef Google Scholar

    [3] QIU Haijun, CUI Peng,REGMI A D,et al. Slope height and slope gradient controls on the loess slide size within different slip surfaces[J]. Physical Geography,2017,38(4):303 − 317. doi: 10.1080/02723646.2017.1284581

    CrossRef Google Scholar

    [4] 彭建兵,林鸿州,王启耀,等. 黄土地质灾害研究中的关键问题与创新思路[J]. 工程地质学报,2014,22(4):684 − 691. [PENG Jianbing,LIN Hungchou,WANG Qiyao,et al. The critical issues and creative concepts in mitigation research of loess geological hazards[J]. Journal of Engineering Geology,2014,22(4):684 − 691. (in Chinese with English abstract) doi: 10.13544/j.cnki.jeg.2014.04.014

    CrossRef Google Scholar

    PENG Jianbing, LIN Hungchou, WANG Qiyao, et al. The critical issues and creative concepts in mitigation research of loess geological hazards[J]. Journal of Engineering Geology, 2014, 22(4): 684-691. (in Chinese with English abstract) doi: 10.13544/j.cnki.jeg.2014.04.014

    CrossRef Google Scholar

    [5] 陈林万,张晓超,裴向军,等. 降雨诱发直线型黄土填方边坡失稳模型试验[J]. 水文地质工程地质,2021,48(6):151 − 160. [CHEN Linwan,ZHANG Xiaochao,PEI Xiangjun,et al. Model test of the linear loess fill slope instability induced by rainfall[J]. Hydrogeology & Engineering Geology,2021,48(6):151 − 160. (in Chinese with English abstract)

    Google Scholar

    CHEN Linwan, ZHANG Xiaochao, PEI Xiangjun, et al. Model test of the linear loess fill slope instability induced by rainfall[J]. Hydrogeology & Engineering Geology, 2021, 48(6): 151-160. (in Chinese with English abstract)

    Google Scholar

    [6] 刘朋飞. 黄土高原地区环境变迁与地质灾害关系研究——以延安地区滑坡为例[D]. 西安: 长安大学, 2010

    Google Scholar

    LIU Pengfei. Study on the environmental change and geological disasters of the loess plateau region: Take the landslide of Yan’an as an example[D]. Xi’an: Changan University, 2010. (in Chinese with English abstract)

    Google Scholar

    [7] 卢永兴,陈剑,霍志涛,等. 降雨与开挖作用下黄土滑坡失稳过程分析—以关中地区长武县杨厂村老庙滑坡为例[J]. 地质科技通报,2022,41(6):95 − 104. [LU Yongxing,CHEN Jian,HUO Zhitao,et al. Analysis of instability process of the loess landslides under rainfall and excavation actions:A case study of Laomiao landslide at Yangchang Village in Changwu County, Guanzhong area[J]. Bulletin of Geological Science and Technology,2022,41(6):95 − 104. (in Chinese with English abstract)

    Google Scholar

    [LU Yongxing, CHEN Jian, HUO Zhitao, et al. Analysis of instability process of the loess landslides under rainfall and excavation actions: a case study of Laomiao landslide at Yangchang Village in Changwu County, Guanzhong area[J]. Bulletin of Geological Science and Technology, 2022, 41(6): 95-104.(in Chinese with English abstract)

    Google Scholar

    [8] 杨志华,吴瑞安,郭长宝,等. 川西巴塘断裂带地质灾害效应与典型滑坡发育特征[J]. 中国地质,2022,49(2):355 − 368. [YANG Zhihua,WU Ruian,GUO Changbao,et al. Geo-hazard effects and typical landslide characteristics of the Batang fault zone in the western Sichuan[J]. Geology in China,2022,49(2):355 − 368. (in Chinese with English abstract)

    Google Scholar

    [YANG Zhihua, WU Ruian, GUO Changbao, et al. Geo-hazard effects and typical landslide characteristics of the Batang fault zone in the western Sichuan[J]. Geology in China, 2022, 49(2): 355-368.(in Chinese with English abstract)

    Google Scholar

    [9] VAN WESTEN C J,VAN ASCH T W J,SOETERS R. Landslide hazard and risk zonation—why is it still so difficult?[J]. Bulletin of Engineering Geology and the Environment,2006,65(2):167 − 184. doi: 10.1007/s10064-005-0023-0

    CrossRef Google Scholar

    [10] 田春山,刘希林,汪佳. 基于CF和Logistic回归模型的广东省地质灾害易发性评价[J]. 水文地质工程地质,2016,43(6):154 − 161. [TIAN Chunshan,LIU Xilin,WANG Jia. Geohazard susceptibility assessment based on CF model and logistic regression models in Guangdong[J]. Hydrogeology & Engineering Geology,2016,43(6):154 − 161. (in Chinese with English abstract)

    Google Scholar

    TIAN Chunshan, LIU Xilin, WANG Jia. Geohazard susceptibility assessment based on CF model and Logistic Regression models in Guangdong[J]. Hydrogeology & Engineering Geology, 2016, 43(6): 154-161. (in Chinese with English abstract)

    Google Scholar

    [11] AYALEW L,YAMAGISHI H. The application of GIS-based logistic regression for landslide susceptibility mapping in the Kakuda-Yahiko Mountains,Central Japan[J]. Geomorphology,2005,65(1/2):15 − 31.

    Google Scholar

    [12] 孙长明,马润勇,尚合欣,等. 基于滑坡分类的西宁市滑坡易发性评价[J]. 水文地质工程地质,2020,47(3):173 − 181. [SUN Changming,MA Runyong,SHANG Hexin,et al. Landslide susceptibility assessment in Xining based on landslide classification[J]. Hydrogeology & Engineering Geology,2020,47(3):173 − 181. (in Chinese with English abstract)

    Google Scholar

    SUN Changming, MA Runyong, SHANG Hexin, et al. Landslide susceptibility assessment in Xining based on landslide classification[J]. Hydrogeology & Engineering Geology, 2020, 47(3): 173-181. (in Chinese with English abstract)

    Google Scholar

    [13] LEE S,RYU J H,WON J S,et al. Determination and application of the weights for landslide susceptibility mapping using an artificial neural network[J]. Engineering Geology,2004,71(3/4):289 − 302.

    Google Scholar

    [14] PRADHAN B. A comparative study on the predictive ability of the decision tree,support vector machine and neuro-fuzzy models in landslide susceptibility mapping using GIS[J]. Computers & Geosciences,2013,51:350 − 365.

    Google Scholar

    [15] 牛瑞卿,彭令,叶润青,等. 基于粗糙集的支持向量机滑坡易发性评价[J]. 吉林大学学报(地球科学版),2012,42(2):430 − 439. [NIU Ruiqing,PENG Ling,YE Runqing,et al. Landslide susceptibility assessment based on rough sets and support vector machine[J]. Journal of Jilin University (Earth Science Edition),2012,42(2):430 − 439. (in Chinese with English abstract)

    Google Scholar

    NIU Ruiqing, PENG Ling, YE Runqing, et al. Landslide susceptibility assessment based on rough sets and support vector machine[J]. Journal of Jilin University (Earth Science Edition), 2012, 42(2): 430-439. (in Chinese with English abstract)

    Google Scholar

    [16] SAITO H,NAKAYAMA D,MATSUYAMA H. Comparison of landslide susceptibility based on a decision-tree model and actual landslide occurrence:The Akaishi Mountains,Japan[J]. Geomorphology,2009,109(3/4):108 − 121.

    Google Scholar

    [17] 杜国梁,杨志华,袁颖,等. 基于逻辑回归-信息量的川藏交通廊道滑坡易发性评价[J]. 水文地质工程地质,2021,48(5):102 − 111. [DU Guoliang,YANG Zhihua,YUAN Ying,et al. Landslide susceptibility mapping in the Sichuan-Tibet traffic corridor using logistic regression-information value method[J]. Hydrogeology & Engineering Geology,2021,48(5):102 − 111. (in Chinese with English abstract)

    Google Scholar

    DU Guoliang, YANG Zhihua, YUAN Ying, et al. Landslide susceptibility mapping in the Sichuan-Tibet traffic corridor using logistic regression-information value method[J]. Hydrogeology & Engineering Geology, 2021, 48(5): 102-111. (in Chinese with English abstract)

    Google Scholar

    [18] 兰恒星,周成虎,伍法权,等. GIS支持下的降雨型滑坡危险性空间分析预测[J]. 科学通报,2003,48(5):507 − 512. [LAN Hengxing,ZHOU Chenghu,WU Faquan,et al. Spatial analysis and prediction of rainfall landslide risk based on GIS[J]. Chinese Science Bulletin,2003,48(5):507 − 512. (in Chinese) doi: 10.3321/j.issn:0023-074X.2003.05.021

    CrossRef Google Scholar

    LAN Hengxing, ZHOU Chenghu, WU Faquan, et al. Spatial analysis and prediction of rainfall landslide risk based on GIS[J]. Chinese Science Bulletin, 2003, 48(5): 507-512. (in Chinese) doi: 10.3321/j.issn:0023-074X.2003.05.021

    CrossRef Google Scholar

    [19] 武利. 基于SINMAP模型的区域滑坡危险性定量评估及模型验证[J]. 地理与地理信息科学,2012,28(2):35 − 39. [WU Li. A SINMAP-based quantitative assessment and model verification of regional landslide hazard[J]. Geography and Geo-Information Science,2012,28(2):35 − 39. (in Chinese with English abstract)

    Google Scholar

    WU Li. A SINMAP-based quantitative assessment and model verification of regional landslide hazard[J]. Geography and Geo-Information Science, 2012, 28(2): 35-39. (in Chinese with English abstract)

    Google Scholar

    [20] 李艳杰,唐亚明,邓亚虹,等. 降雨型浅层黄土滑坡危险性评价与区划—以山西柳林县为例[J]. 中国地质灾害与防治学报,2022,33(2):105 − 114. [LI Yanjie,TANG Yaming,DENG Yahong,et al. Hazard assessment of shallow loess landslides induced by rainfall:A case study of Liulin County of Shanxi ProvinceFull text replacement[J]. The Chinese Journal of Geological Hazard and Control,2022,33(2):105 − 114. (in Chinese with English abstract)

    Google Scholar

    LI Yanjie, TANG Yaming, DENG Yahong, et al. Hazard assessment of shallow loess landslides induced by rainfall: a case study of Liulin County of Shanxi ProvinceFull text replacement[J]. The Chinese Journal of Geological Hazard and Control, 2022, 33(2): 105-114. (in Chinese with English abstract)

    Google Scholar

    [21] HE Jianyin, QIU Haijun, QU Feihang,et al. Prediction of spatiotemporal stability and rainfall threshold of shallow landslides using the TRIGRS and Scoops3D models[J]. CATENA,2021,197:104999. doi: 10.1016/j.catena.2020.104999

    CrossRef Google Scholar

    [22] 吕佼佼,范文,吕远强. 考虑土层深度分布的浅层滑坡危险性评价—以陕西秦巴山区为例[J]. 灾害学,2018,33(2):218 − 223. [LYU Jiaojiao,FAN Wen,LYU Yuanqiang. Hazard assessment of shallow landslide considering soil depth distribution—A case study of qinba mountains in Shaanxi Province[J]. Journal of Catastrophology,2018,33(2):218 − 223. (in Chinese with English abstract) doi: 10.3969/j.issn.1000-811X.2018.02.038

    CrossRef Google Scholar

    LYU Jiaojiao, FAN Wen, LYU Yuanqiang. Hazard assessment of shallow landslide considering soil depth distribution—a case study of qinba mountains in Shaanxi Province[J]. Journal of Catastrophology, 2018, 33(2): 218-223. (in Chinese with English abstract) doi: 10.3969/j.issn.1000-811X.2018.02.038

    CrossRef Google Scholar

    [23] 姚杰,李秀珍,徐瑞池. 降雨条件下拟建川藏铁路典型段潜在滑坡三维稳定性动态识别研究[J]. 防灾减灾工程学报,2021,41(3):422 − 431. [YAO Jie,LI Xiuzhen,XU Ruichi. Dynamic identification of three-dimensional stability of potential landslides in a typical section of the proposed Sichuan-Tibet railway under rainfall conditions[J]. Journal of Disaster Prevention and Mitigation Engineering,2021,41(3):422 − 431. (in Chinese with English abstract)

    Google Scholar

    YAO Jie, LI Xiuzhen, XU Ruichi. Dynamic identification of three-dimensional stability of potential landslides in a typical section of the proposed Sichuan-Tibet railway under rainfall conditions[J]. Journal of Disaster Prevention and Mitigation Engineering, 2021, 41(3): 422-431. (in Chinese with English abstract)

    Google Scholar

    [24] WEIDNER L,DEPREKEL K,OOMMEN T,et al. Investigating large landslides along a river valley using combined physical,statistical,and hydrologic modeling[J]. Engineering Geology,2019,259:105169. doi: 10.1016/j.enggeo.2019.105169

    CrossRef Google Scholar

    [25] PACK R T, TARBOTON D G, GOODWIN C N. The SINMAP approach to terrain stability mapping. Proceedings of the 8th congress of the International Association of Engineering Geology. Netherlands: A Balkema Publisher, 1998. 1157-1165.

    Google Scholar

    [26] 武利,张万昌,张东,等. 基于遥感与地理信息系统的分布式斜坡稳定性定量评估模型[J]. 地理科学,2004,24(4):458 − 464. [WU Li,ZHANG Wanchang,ZHANG Dong,et al. Remote sensing & GIS-based distributed hillslope stability:quantitative evaluation model[J]. Scientia Geographica Sinica,2004,24(4):458 − 464. (in Chinese with English abstract) doi: 10.3969/j.issn.1000-0690.2004.04.012

    CrossRef Google Scholar

    WU Li, ZHANG Wanchang, ZHANG Dong, et al. Remote sensing & GIS-based distributed hillslope stability: quantitative evaluation model[J]. Scientia Geographica Sinica, 2004, 24(4): 458-464. (in Chinese with English abstract) doi: 10.3969/j.issn.1000-0690.2004.04.012

    CrossRef Google Scholar

    [27] 康超,谌文武,张帆宇. 基于DEM的分布式斜坡稳定性模型在黄土沟壑区浅层滑坡中的应用[J]. 中南大学学报(自然科学版),2010,41(5):1987 − 1992. [KANG Chao,CHEN Wenwu,ZHANG Fanyu. Application of distributed hillslope stability model based on DEM to stability of shallow landslide of the loess gully area[J]. Journal of Central South University (Science and Technology),2010,41(5):1987 − 1992. (in Chinese with English abstract)

    Google Scholar

    KANG Chao, CHEN Wenwu, ZHANG Fanyu. Application of distributed hillslope stability model based on DEM to stability of shallow landslide of the loess gully area[J]. Journal of Central South University (Science and Technology), 2010, 41(5): 1987-1992. (in Chinese with English abstract)

    Google Scholar

    [28] 麦鉴锋,冼宇阳,刘桂林. 气候变化情景下广东省降雨诱发型滑坡灾害潜在分布及预测[J]. 地球信息科学学报,2021,23(11):2042 − 2054. [MAI Jianfeng,XIAN Yuyang,LIU Guilin. Predicting potential rainfall-triggered landslides sites in Guangdong Province(China)using MaxEnt model under climate changes scenarios[J]. Journal of Geo-Information Science,2021,23(11):2042 − 2054. (in Chinese with English abstract) doi: 10.12082/dqxxkx.2021.210182

    CrossRef Google Scholar

    MAI Jianfeng, XIAN Yuyang, LIU Guilin. Predicting potential rainfall-triggered landslides sites in Guangdong Province(China)using MaxEnt model under climate changes scenarios[J]. Journal of Geo-Information Science, 2021, 23(11): 2042-2054. (in Chinese with English abstract) doi: 10.12082/dqxxkx.2021.210182

    CrossRef Google Scholar

    [29] CHEN W,POURGHASEMI H R,KORNEJADY A,et al. Landslide spatial modeling:introducing new ensembles of ANN,MaxEnt,and SVM machine learning techniques[J]. Geoderma,2017,305:314 − 327. doi: 10.1016/j.geoderma.2017.06.020

    CrossRef Google Scholar

    [30] 万洋,郭捷,马凤山,等. 基于最大熵模型的中尼交通廊道滑坡易发性分析[J]. 中国地质灾害与防治学报,2022,33(2):88 − 95. [WAN Yang,GUO Jie,MA Fengshan,et al. Landslide susceptibility assessment based on MaxEnt model of along Sino-Nepal traffic corridor[J]. The Chinese Journal of Geological Hazard and Control,2022,33(2):88 − 95. (in Chinese with English abstract) doi: 10.16031/j.cnki.issn.1003-8035.2022.02-11

    CrossRef Google Scholar

    WAN Yang, GUO Jie, MA Fengshan, et al. Landslide susceptibility assessment based on MaxEnt model of along Sino-Nepal traffic corridor[J]. The Chinese Journal of Geological Hazard and Control, 2022, 33(2): 88-95. (in Chinese with English abstract) doi: 10.16031/j.cnki.issn.1003-8035.2022.02-11

    CrossRef Google Scholar

    [31] PHILLIPS S J, ANDERSON R P, SCHAPIRE R E. Maximum entropy modeling of species geographic distributions[J]. Ecological Modelling, 2006, 190(3/4): 231 − 259.

    Google Scholar

    [32] YANG Jilin,DONG Jinwei,XIAO Xiangming,et al. Divergent shifts in peak photosynthesis timing of temperate and alpine grasslands in China[J]. Remote Sensing of Environment,2019,233:111395. doi: 10.1016/j.rse.2019.111395

    CrossRef Google Scholar

    [33] 杨文璐,邱海军,裴艳茜,等. 典型黄土丘陵区浅层黄土滑坡稳定性评价—以延安市志丹县为例[J]. 第四纪研究,2019(2):408 − 419. [YANG Wenlu,QIU Haijun,PEI Yanqian,et al. Evalution of shallow loess landslide stability in typical loess hilly region:a case study of Zhidan County in Yan'an area of Shaanxi Province[J]. Quaternary Sciences,2019(2):408 − 419. (in Chinese with English abstract) doi: 10.11928/j.issn.1001-7410.2019.02.13

    CrossRef Google Scholar

    YANG Wenlu, QIU Haijun, PEI Yanqian, et al. Evalution of shallow loess landslide stability in typical loess hilly region: a case study of Zhidan County in Yan'an area of Shaanxi Province[J]. Quaternary Sciences, 2019(2): 408-419. (in Chinese with English abstract) doi: 10.11928/j.issn.1001-7410.2019.02.13

    CrossRef Google Scholar

    [34] 国家质量监督检验检疫总局, 中国国家标准化管理委员会. 降水量等级: GB/T 28592—2012[S]. 北京: 中国标准出版社, 2012

    Google Scholar

    General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China, Standardization Administration of the People’s Republic of China. Grade of precipitation: GB/T 28592—2012[S]. Beijing: Standards Press of China, 2012. (in Chinese)

    Google Scholar

    [35] 王丽英,王红梅,郭盈盈,等. 基于不同建模数据的陕西省志丹县滑坡易发性分区[J]. 人民长江,2021,52(12):99 − 106. [WANG Liying,WANG Hongmei,GUO Yingying,et al. Landslide susceptibility mapping based on differentiated modeling data in Zhidan County,Shaanxi Province[J]. Yangtze River,2021,52(12):99 − 106. (in Chinese with English abstract)

    Google Scholar

    WANG Liying, WANG Hongmei, GUO Yingying, et al. Landslide susceptibility mapping based on differentiated modeling data in Zhidan County, Shaanxi Province[J]. Yangtze River, 2021, 52(12): 99-106. (in Chinese with English abstract)

    Google Scholar

    [36] 谢定义, 邢义川. 黄土土力学[M]. 北京: 高等教育出版社, 2016

    Google Scholar

    XIE Dingyi, XING Yichuan. Soil mechanics for loess soils[M]. Beijing: Higher Education Press, 2016. (in Chinese)

    Google Scholar

    [37] 郭靖,骆亚生,郭鸿,等. 不同地区黄土的结构性试验研究[J]. 水土保持通报,2010,30(1):89 − 92. [GUO Jing,LUO Yasheng,GUO Hong,et al. Experimental study on structural characteristics of loess in different regions[J]. Bulletin of Soil and Water Conservation,2010,30(1):89 − 92. (in Chinese with English abstract)

    Google Scholar

    GUO Jing, LUO Yasheng, GUO Hong, et al. Experimental study on structural characteristics of loess in different regions[J]. Bulletin of Soil and Water Conservation, 2010, 30(1): 89-92. (in Chinese with English abstract)

    Google Scholar

  • 加载中
通讯作者: 陈斌, bchen63@163.com
  • 1. 

    沈阳化工大学材料科学与工程学院 沈阳 110142

  1. 本站搜索
  2. 百度学术搜索
  3. 万方数据库搜索
  4. CNKI搜索

Figures(12)

Tables(6)

Article Metrics

Article views(1847) PDF downloads(112) Cited by(0)

Access History

Other Articles By Authors

Catalog

    /

    DownLoad:  Full-Size Img  PowerPoint