Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography, Vol. 31, No. 6-2, 529-538, 2013 http://dx.doi.org/10.7848/ksgpc.2013.31.6-2.529 Application of Remote Sensing and GIS technology for monitoring coastal changes in estuary area of the Red river system, Vietnam Pham Thi Lan1) · Tong Si Son2) · Kavinda Gunasekara3) · Nguyen Thi Nhan4)· La Phu Hien5) Abstract Coastline is the most dynamic part of seascape since its shape is affected by various factors. Coastal zone is an area with immense geological, geomorphological and ecological interest. Monitoring coastal change is very important for safe navigation, coastal resource management. This paper shows a result of monitoring coastal morphological changes using Remote Sensing and GIS. Study was carried out to obtain intensity of erosion, deposition and sand bar movement in the Red River Delta. Satellite images of ALOS/AVNIR-2 and Landsat were used for the monitoring of coastal morphological changes over the period of 1975 to 2009. Band rationing and threshold technique was used for the coastline extraction. Tidal levels at the time of image acquisition varied from -0.89m to 2.87m. Therefore, coastline from another image at a different tidal level in the same year was considered to get the corrected coastline by interpolation technique. A series of points were generated along the coastal line from 1975 image and were established as reference points to see the change in later periods. The changes were measured in Euclidean distances from these reference points. Positive values represented deposition to the sea and negative values are erosion. The result showed that the Red river delta area expanded to the sea 3500m in Red river mouth, and 2873m in Thai Binh river mouth from 1975 to 2009. The erosion process occurred continuously from 1975 up to now with the average magnitude 23.77m/year from 1975 to 1989 and 7.85m/year from 2001 to 2009 in Giao Thuy area. From 1975 to 2009, total 1095.2ha of settlement area was eroded by sea. On the other hand, land expanded to the sea in 4786.24ha of mangrove and 1673.98ha of aquaculture. Keywords : Coastal morphological, coastal line extraction, coastal erosion, sand bar movement 1. Introduction affected by different factors, such as hydrography, geology, climate, and vegetation (Guariglia et al. 2006). All these The coastal zone is currently a sensitive policy area for factors contribute to change the coastline morphology. those involved with its management. Phenomena such as In addition to natural factors, human activities, such as erosion and landslides affect the stability of both the natural building dyke, expanded land and aquaculture also play and the built environment (Mills et al. 2005). The coastline a main role in modifying coastline. Therefore, a research is defined as the boundary between land and a water of coastal morphological is needed to define the levels, surface (Boak and Turner 2005; Guariglia et al. 2006). forms and period of erosion and deposition and sand bar It is the most dynamic part of seascape since its shape is movement over years. After that, we can predict the trend, 1) Faculty of Geodesy, Hanoi University of Mining and Geology, Vietnam (Email: [email protected]) 2) Space Technology Institute, Vietnam Academy of Science and Technology (Email:[email protected]) 3) Geoinformatics Center, Asian Institute of Technology (Email: [email protected] ) 4) Institute of Marine Geology and Geophysis, Vietnam Academy of Science and Technology (Email: [email protected]) 5) Faculty of Geodesy, Hanoi University of Mining and Geology, Vietnam (Email: [email protected]) This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http:// creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. 529 Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography, Vol. 31, No. 6-2, 529-538, 2013 find out the causes and propose solutions to degrade the consequence of the erosion and deposition. On another hand, the statistic of what type of land use and how many land area was taken to the sea over time is indispensable. Based on the information we can know the driving factors, which can provide relevant information for coastal resource management, environmental protection and for planning sustainable development of coastal areas. Traditional coastline mapping in small areas is carried out using conventional field surveying methods. Over last century, the popular method for delineating the shoreline is Fig. 1. Coastal area of Red river delta analytical stereo photogrammetry using tide-coordinated aerial photography controlled by kinematic GPS techniques 2. Study area and materials (NOAA 1997). Nowadays, remote sensing technique, which can provide synoptic view, multispectral and high 2.1 Study area resolution data, plays an important role for monitoring The Red River Delta in the North of Vietnam is characterized and mapping coastal areas (Doydee 2005). Accuracy of by a triangular shaped low-lying delta plain that developed coastline extraction from satellite image depends on water during the major part of the Holocene (Hoekstra et al. 2007). line, tidal level and several other conditions. Variations in It has length of 130 km coastline beside Gulf of Tonkin, it coastline position can be: long-term, cyclical, random, due covers five districts as Tien Lang (Hai Phong province); Thai to specific events (Guariglia et al. 2006). This study used Thuy and Tien Hai (Thai Binh province); Giao Thuy, Nghia the band rationing method that is rationed between band Hung and Hai Hau (Nam Dinh province). The study area (see 4 and 2 for Advanced Land Observing Satellite (ALOS) Fig. 1) has seven large mouths of rivers along the coastline. image and Landsat MSS, and between band 5 and 2 for This coastline follows Northeastern to Southwestern direction Landsat TM, ETM. starting from Van Uc estuary and ending up to Day estuary. Song Hong, the Red river, is the largest river in northern Vietnam provides and forms a great delta before entering 2.2 Materials the Gulf of Tonkin. Red river delta area is an intensely Maps and satellite images are the main materials in this developed and densely populated area. Along the coastal research. We were provided a topographic map at scale line of Red river delta there are both phenomena occurring 1/50000 built in 2002 from Center of Surveying and Map included erosion and deposition, that makes the coastline Data (COSAMD). Tide level table from 1975 to 2009 for each change is complex and fast. By using advantages of hour from Hondau station and statistical data of direction remote sensing and GIS technology, this paper aims to: and speed of sea flow along the coastline was provided by i) detect the coastline position from satellite images, ii) Institute of Marine Geology and Geophysis (IMGG). analyze and assess the magnitude and direction of erosion, Satellite images, which are used for extracting deposition as well as sand bars movement. Information coastline, include: Landsat MSS, TM, ETM+ images free derived from this paper will provide the overview of downloaded from Global Visualization Viewer (GLOVIS), coastal morphological change in the past and trend of the United States Geological Survey (USGS), and ALOS- coastal line changes in the future in the Red river delta Advanced Visible and Near Infrared Radiometer type 2 area in Vietnam. Moreover monitoring of land use change (ALOS AVIRNIR-2) images provided by Japan Aerospace is also concerned as the consequence of the coastal Exploration Agency (JAXA). List of satellite image and morphological changes. tidal heights at acquisition times was shown in table 1. 530 Application of Remote Sensing and GIS technology for monitoring coastal changes in estuary area of the Red river system, Vietnam Table 1. List of satellite images and tidal heights at acquisition times Images Sensor ParthRow Date Local Time Resolution Tidal height (m) Landsat 2 MSS 136046 12/29/1975 9h40' 80 1.14 Landsat 5 TM 126046 11/23/1989 9h39' 30 -0.20 Landsat 4 TM 126046 4/21/1989 9h51' 30 0.47 Lansat 7 ETM+ 126046 11/16/2001 10h6' 30 -0.89 Lansat 7 ETM+ 126046 9/29/2001 10h5' 30 0.53 Lansat 7 ETM+ 126046 10/5/2009 10h7' 30 0.81 Lansat 7 ETM+ 126046 11/6/2009 10h8' 30 2.87 201603200 ALOS AVINIR-2 201603190 11/6/2009 10h38' 10 2.45 201603180 3. Methodology In this reaearch, remote sensing technology is used to detect water lines and calculate land use change from satellite images To complete the purposes of this research, a series of over the years. Water lines are input data for spatial analysis remote sensing and spatial analysis methods are implemented in GIS sub-methods, which are contour interpolation method from preprocessing images, images analysis, modeling, to correct effect of tidal lever, linear direction mean method and analysis vector data in GIS. A general method for this to monitor sand bars movement, control points to monitor research is shown in Fig. 2. erosion, deposition, and intersect multi-temporal data to define the area of erosion or deposition. A field trip in 1 week has carried out along the coastal line to collect information about history of erosion, human activities effect to coastal line change, location of water lines at the highest and lowest tidal lever. In situ data plays very importance role in validate and assessment the change of coastal morphology as so as provided the evidences to define the driving factors of change. 3.1 Images pre-processing After data covering the study sites in the respective period were obtained, a data preprocessing phase was performed to prepare the data for the experiments.