Topographical Change Monitoring for Susceptible Landslide Area Determination by Using Multi-Date Digital Terrain Models and LiDAR

Transcription

1 Topographical Change Monitoring for Susceptible Landslide Area Determination by Using Multi-Date Digital Terrain Models and Chanist PRASERTBURANAKUL 1, Parkorn SUWANICH 2, Kanchana NAKHAPAKORN 3, and Sukit VISESHSIN 4 Faculty of Environment and Resource Studies, Mahidol University, Thailand: 1 chanist.p@gmail.com 2 enpsn@mahidol.ac.th 3 enknk@mahidol.ac.th 4 ESRI(Thailand) Co.Ltd: sukit.v@cdg.co.th One of the significant appearances of landslide disaster is topographical change, which possibly affects to vulnerable community in landslide hazard area. Considering the available advanced technology, in particular Light Detection and Ranging () technology and high resolution imagery, the body of knowledge regarding landslide studies has been explored and conducted to protect human lives in several ways. Thus, this study attempts to express an advanced technique to investigate the topographical change regarding the 2001-landslide event in Ban Nam Koh Village, Petchabun, Thailand. Consequently, the Digital Terrain Model (DTM), generated from technology, and multi-date aerial photos in 2002, 2007, and 2010 are applied in this study. Accordingly, tree canopies have been extracted from the DTM of technology and discriminated the opened areas from soil mobilization and erosion scars on those multi-date aerial photos. Regarding with this technique, the topographical changes are presented on those multi-date aerial photos through timeline based on the extracted 2002-Digital Elevation Model (DEM). The output of this study presents the landslide susceptibility maps determined from scar-scouring inventory data and soil mobilization and erosion scars along the river banks within Geographical Information System (GIS) platform. Eventually, this study is useful to several tasks in local administrations, for instance, local disaster management and landslide monitoring to investigate the topographical change in landslide hazard areas. Key Words: Landslide, Topographical Change, DEM and 1. INTRODUCTION In general, the topographical factors easily causes landslide phenomenon consist of high degree of slopes, aspect, slope length, topographic type, geologic properties, and terrain elevation. Especially, the slope of topographic area is significant. 1) In Thailand, it is important in preparation of landslide hazard maps and currently government agencies and many researchers have developed an effective risk map. Refer to landslide basis theory, the landslide risk map is indispensable to use landslide susceptibility, landslide hazard map, vulnerable people information, element at risk data and landslide inventory map is processed in various map scales (at small scale, medium scale, and large scale) and specific site 2). For the most effective landslide hazard and risk map, they require high accurate digital elevation model (DEM) that was acquired by technology (Light Detection and Ranging). Typically, the points measurement are fired to the land cover so called Digital Surface Model which contain information on all measurable object s of the earth s surface 3).This research focuses on comparing and evaluating the effects of land cover and topographical terrain where had been changed from landslide incident in 2001 which has been interpreted from aerial photographs. In addition, was applied for land cover information extraction, to assess the land cover and land use changes. The importance of DTM and for analyzing the appearance of landslide disasters is the visual interpretation of landslide phenomena from shaded relief images generated from DEMs which have

2 been cleaned in kind of bare earth DEMs 4) The use of shaded relief images of DEMS provides the researcher much more detailed interpretation of the landslide mechanism as the deformation features in the large landslide are visible and landslide can be mapped in heavily forested area 5). Actually the surface characteristics such as internal deformation structures fissures, tension cracks, flow lobes, step like morphology and scraps are detectable if the detail of the DEM or DTM is sufficiently large. 6) The subtraction of DEMs allows the researcher to visualize the displacement of landslide has taken place and calculating the displacement of volume. 7) 2. OBJECTIVE To monitor the topographical change in area of landslide have occurred by using multi-date of DEM. The land use change was assessed as the factors that cause landslides in the area by using and high-resolution aerial photographs. 3. METHODOLOGY (1) Study Area Ban Nam Koh Village, Lom Sak nearby Phetchabun Mountain Range and has the Koh River flowing all year round. Many villages populated along the river. The main occupation here is rice cultivation, the minor occupation is cultivation of tobacco and corn. In this district has 6,691 peoples, density of peoples per sq. km. the number of households are 1,946 households. The study area where covering some part of Tambon Ban Nam Koh, Amphoe Lom Sak, Petchabun Province covering Nam Ko Yai catchment where has an area of approximately 111 km 2. It located in north of Thailand at coordinate in easting 718,942 and northing 1,869,131 (Upper left corner) to easting 735,377 and northing 1,854,460 (Lower right corner) of UTM coordinate system, WGS84 datum Zone 47. Fig.1 Study area: Ban Nam Koh Village, Lom Sak, District of Phetchabun province (2)Method The researching method begins on collection of DEMs and data acquisition. The ortho photo was generated by using photogrammetry technique and high density of topographic terrain by technology. data were processed into raster surface data by parameterization of progressive TIN densification techniques 8). After all gathering and processed data were done completely, the change analysis are carried out later on. The multi-date DEMs data consists of DEMs acquired on 2002 after six months of landside incident in Ban Nam Koh village, DEMs by acquired on 2007 and 2010 at a flying height of 2 kilometers with density spacing at 2 meters. The terrain elevation, slope and land cover were extracted by using this particular data set. The difference of height and volume were calculated according to the multi-date DEMs. In this study, the research focused in 2 cases; firstly comparing of DEM of 2002 and of 2010 in Nam Koh Yai sub-basin and secondly focusing on selected three small areas where having the much more changes of topographic and land cover. The image algebra by using GIS-based tool will be applied for assessment. The height difference, the volume of terrain loss, land cover change and slope difference will be assessed and detect the change for susceptible landslide area determination

3 Fig.2 Illustrates the research workflow (3) Data Collection The spatial data in this research includes the multi-date DEMs and ortho photo. Table 1 shows the data properties which consist of the data acquired date, technique of data production, spatial resolution and vertical accuracy. The was acquired at height 6,500 feet above ground level and 45,000Hz of pulse rate and 35 Hz of scanning rate. Table 1 The properties of spatial data were applied in this research. Data type /Date Producing Spatial Vertical Technique Resolution Accuracy DEMs of 2002 Photogrammetry 5 m 2.5 m DEMs of m <0.15 m DEMs of m <0.15 m Ortho of 2002 photogrammetry 0.50 m 1 m Ortho of 2007 photogrammetry 0.20 m 1 m Ortho of 2010 photogrammetry 0.20 m 1m 4. RESULTS (1) Result of topographic change by comparing the DEM and land cover of year 2002 and The below figures illustrates the results of the assessment of changes in topography in the study area. Fig. 3 illustrates the ortho photo of 2002 and 2010 were used for assessment. Fig.4 represents the difference of height between 2002 and The dark blue color represents the volumetric of terrain loss and red color represents the increasing of volumetric in this area. Table 2 shows the statistic of topographic change by analyzing with elevation and slope factors

4 Fig.3 Illustrates the color ortho photo of 2002(Left) and 2010(Right) Fig.4 A) illustrates the difference of height between 2002 and The dark blue color represents the volumetric of terrain loss and red color represents the increase of volume in this area. B) Illustrates the difference of slope between 2002 and 2010 Table 2 shows the statistic data of DEM of 2002 generated by area-based matching and stereo-editing of photogrammetry technique together with high accuracy DEM by technology to assess the height of the terrain and the percent slope of the Nam Koh Yai sub-basin as shown below. Table 2 The changes in elevation and slope in study area Elevation change Between DEM2002 and 2010 Slope change Between DEM2002 and 2010 Changes less than 5% km km 2 Changes between 5-10% 8.83 km km 2 Changes more than 10% 2.60 km km

5 The topographic change was detected in the study area, the change of topographic and slope in catchment area is dramatically distinguished due to dam construction for irrigation and prevent the debris flow from the mountain. There are a steep slopes and elevation change between 2 dates. The west of Ban Nam Koh village, some areas have changed because the land mass was lost and gained. However, as you can see the river bank where the stream is highly eroded and can be seen as a form of change along the waterfront. As well, the changes in the river bank can be seen clearly in the aerial photograph for both times. In some areas the river bank is wider and there are some areas where the river narrows as land cover with a density increase. The result of elevation change is about km 2. The slope change between 2002 and 2010 is about 22.8 km 2. Table 3 The statistics of land cover change in study area. Study area Land cover extracted km 2 by ortho photo of 2002 Land cover extracted by of 2010 Bare ground earth area km km 2 Tree covering area km km 2 higher than 5 meter n/a km 2 The height of trees between 4-5 meter n/a 4.85 km 2 The height of trees between 3-4 meter n/a 5.28 km 2 The height of trees between 2-3 meter n/a 6.13 km 2 The height of trees between 1-2 meter n/a 8.34 km 2 Table 3 represents the statistic data of land cover in 2002 and can extract the land cover by using the height of tree. In Table 3, it shows that the bare ground earth area was decreased and the tree covering area was increased. The advantage of is that the capacity of estimation the tree height. The 2 tree is higher than 5 meters covering km. (2)The assessment of topographic change in selected 3 study areas. The topographical change assessment of the study area can be categorized into 3 selected study areas. The data sources were evaluated by using DEMs and ortho photo of 2002 and DEMs by of 2007 and 2010 are as follows: Area 1: Fig.6 A and B represent the topographic change can be seen significantly from 2007 and The topographic color slices of both figures represent the change shows in the light color from dark. The land mass change (Fig.6 B and C) from the ortho photos can be seen obviously. From the results of the volume, it can be seen that there is a significant volume change in the area (see Table 4)

6 Fig.6 DEMs by and Ortho Photo of 2007 and 2010 in Area1. Table 4 The statistics of topographic change in study area 1 Study area 1 DEM 2002 (1.29 km 2 ) DEM 2007 DEM 2010 Minimum Maximum Mean Standard Deviation Volume Calculation Volume Change between Volume Change between and and 2010 Volume Net Loss (m 3 ) 2,454,276 1,876,895 Volume Net Gain (m 3 ) -912, ,349 Area 2; Fig. 7 illustrates the topographic surface was changed significantly from the 2007 that it can be seen from. Fig.7B and C represent the land mass increased. Fig.7E and F illustrate the ortho photos that represent the constructed area for Nam Koh irrigation dam. Result of volumetric calculation was calculated and it s changed significantly

7 Fig.7 DEMs by and Ortho Photo of 2007 and 2010 in Area 2. Table 5 The statistics of topographic change in study area 2 Area 2 DEM 2002 (1.35 km 2 ) DEM 2007 DEM 2010 Minimum Maximum Mean Standard Deviation Volume Calculation Volume change between Volume change between and and 2010 Volume Net Loss (m 3 ) 2,629, ,257 Volume Net Gain (m 3 ) -1,950,673-5,316,509 Area3: Fig.8 represents the mountainous area where the land use was changed significantly by The land use activity fades out from forest class to agricultural class (Fig.12 B and C). In ortho photos, the agricultural crops such as wild tamarind and teak forests was planted in this area where be seen significantly by volumetric change (see table 6)

8 Fig.8 DEMs by and Ortho Photo of 2007 and 2010 in area 3 Table 6 The statistics of topographic change in study area 3 Study are 3 DEM 2002 (1.34 km 2 ) DEM 2007 DEM2010 Minimum Maximum Mean Standard Deviation Volume Calculation Volume Change between Volume Change between and and 2010 Volume Net Loss (m 3 ) 4,427,358 1,252,040 Volume Net Gain (m 3 ) -1,657, , CONCLUSION & RECOMMENDATION The topographic and land use change assessment of the study area by using DEMs and high-resolution in multi-date can be illustrated significantly how the terrain and land cover were changed over time. The height of tree from is able to present the density of tree and the bare earth where can be used for landslide management in local area. The change of terrain and land cover can be applied for susceptible landslide area extraction. The movement of soil near the river bank zone can be depicted easily by. This result can be used for planning of the disaster management and monitoring of landslides in the community. The usage of different source of data may incur with uncertainty and due to technology limitations of the survey. The collecting and data processing the height of the terrain by using the aerial photograph is likely to cause uncertainty in the measurement. The classification and quality checking would be considered closely. The using in small local community in risk area is possible if they have the budget

9 REFERNCES 1) Suwanich, Parkorn. (2009). GEOHAZARD: Learning and Management. Bangkok. Kumpeewan (In Thai) 2) Highland, L., P. T. Brobrowsky, et al. (2008). The Landslide Handbook: A Guide to Understanding Landslides. Reston, Va., U.S. Geological Survey. 3)Ackermann, F. (1999). "Airborne Laser Scanning - Present Status and Future Expectation." ISPRS Journal of Photogrammetry and Remote Sensing 54: 3. 4) Haugerud, R.A., Harding, D.J.,Johnson, S.Y.,Harless, J.L.,Weaver, C.S.,Sherrod, B.L. (2003) High-resolution topography of the Puget Lowland, Wahsington, A Bonanza for Earth Science. GSA Today 13, ) Haneberg, WC. (2004) The ins and outs of airborne : An introduction for practicing engineering geologists, AEG News 48(1), ) Van Westen C.J.(2008) Spatial data for landslide susceptibility, Hazard, and vulnerability assessment: An overview Engineering Geology 102 ( ) 7) Oka, N., (1998). Application of photogrammetry to the field observation of failed slopes Engineering Geology 50(1-2), ) K.A Razak, M. W. S., C.J van Westen, et al. (2011). "Airborne laser scanning of forested landslide characterization: Terrain model quality and visualization." Geomorphology: