As low-lying areas, deltas are sensitive to changes associated with advance taking place on the land and in the ocean. The pattern of change in shoreline positions over time can be used as an indicator of changes in land and/or ocean environments. Land development and rapid population and economic growth can cause subsidence due to excess groundwater extraction, reduction of river sediment supply by dams, and floodplain engineering. Global eustatic and local relative sea-level changes can also significantly affect the coastline of the lowland area. The main purpose of this study is to investigate the causes of shoreline change in the Chao Phraya (CPY) River delta in Thailand, which is a coastal region dominated by intertidal mudflats. This study focuses on river sediment supply, relative sea level change, and mangrove deforestation. Long-term historical data coupled with field observation were used to determine how these factors are related to shoreline retreat of the delta coastline. Shoreline change evaluation for the Upper Gulf of Thailand, including the Chao Phraya estuary between 1954 and 2013, are based on a series of aerial photographs and satellite imagery. This data set represents historical shoreline positions with time intervals ranging from 2 years to 24 years. The shoreline data were converted into vectorized ArcGIS shapefiles and analyzed using the USGS Digital Shoreline Analysis System ArcGIS extension. River survey data collected during the period 2011-2013 were used for studying the characteristics of river flow and sediment transport in the river system. During the period 2011-2013, the flow and sediment characteristics of rivers were measured 9 times at 8 stations in the Ping, Wang, Yom, Nan, and Chao Phraya rivers. The data cover wet season and dry season flow conditions, including the extreme flood event during 2011. Additionally, sediment deposition rates at the Chao Phraya River mouth were estimated from two sediment cores taken from the Chao Phraya River mouth using 210Pb radiometric dating. The results of this study indicate that relative sea-level rise due to the extremely high rate of land subsidence is the major cause of rapid shoreline change in the CPY Delta, and is responsible for 56 and 63 percent of shoreline retreat in the western and eastern portions of the Chao Phraya Delta, respectively. Unlike other major deltas in the southeast and east Asia, the severe shoreline recession during the period 1954-2013 is not strongly related to sediment supply reduction associated with large dam impoundments. Conversely, sediment deposition rates at the CPY Delta tended to increase after 1994 (30 and 22 years after construction of the Bhumibol and Sirikit Dams, respectively). However, the observed average rate of sediment deposition (8-10 mm/year) is less than the average rate of relative sea-level rise (17 mm/year), and the sediment supply from the CPY is not sufficient to balance land loss due to the rise of sea-level during the past six decades. For land-use changes, most of the vegetation areas, especially mangrove forest bounding along the edge of the shoreline, have been converted into aquacultural farmland by 1994. Results from mangrove area analysis over the period 1954-2013 reveal that the reduction of shoreline retreat rates in the eastern CPY was not directly associated with an increase in mangrove areas undergoing reforestation, and mangrove reforestation could not be cited as a shoreline builder or effective measure for coastal protection for coastlines that are rapidly retreating due to land subsidence. However, conversion of mangrove areas into aquaculture farmland can magnify shoreline retreat caused by relative sea-level rise. Results of this study may provide a useful analog for other coastal regimes of the Earth that may experience the effect of the predicted 1-2 meter rise over the next century associated with global warming. / A Dissertation submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Summer Semester 2016. / June 7, 2016. / muddy coast, relative sea-level change, Sedimentation, sediment supply, sediment transport, shoreline change / Includes bibliographical references. / Stephen A. Kish, Professor Co-Directing Dissertation; Joseph F. Donoghue, Professor Co-Directing Dissertation; James B. Elsner, University Representative; William C. Burnett, Committee Member; William C. Parker, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_366034 |
| Contributors | Bidorn, Butsawan (authoraut), Kish, Stephen A. (professor co-directing dissertation), Donoghue, Joseph F. (Joseph Francis) (professor co-directing dissertation), Elsner, James B. (university representative), Burnett, William C. (committee member), Parker, William C., 1952- (committee member), Florida State University (degree granting institution), College of Arts and Sciences (degree granting college), Department of Earth, Ocean, and Atmospheric Science (degree granting department) |
| Publisher | Florida State University, Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text |
| Format | 1 online resource (209 pages), computer, application/pdf |
| Rights | This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). The copyright in theses and dissertations completed at Florida State University is held by the students who author them. |
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