Flood Monitoring And Analysis Over The Middle Reaches Of Yangtze River Basin With MODIS Time-Series Imagery

In recent years, with the growing changes of climate and environment, natural disasters have become more and more frequent. Flood disaster is one of the natural disasters with the high frequency in our country, especially in the middle reaches of the Yangtze River where the flood happened almost every year. The satellite data has the advantages of wide coverage, speed monitoring, low cost and is easy to be carried for the long-term dynamic monitoring. Therefore, remote sensing has replaced the traditional monitoring of flood disaster and become an efficient tool for flood monitoring. With the advantage of higher temporal resolution, higher spatial resolution, higher spectral resolution, wide coverage, accurate radiation correction, and free-cost, MODIS thus has become a better choice for long-term dynamic monitoring of disaster. The purpose of this study is to monitor the flooding area in the middle reaches of Yangtze River during 2000-2010 with 250-m MODIS time-series data, and calculate the emerged depth and evaluate the losses of land and population.The study first discussed the theory and method of water monitoring. Then from the spectral characteristics of water, it introduces several methods and models of water monitoring for TM images, MODIS images, NOAA/AVHRR images and some other optical images and microwave images. Finally, monitoring the flooding area in the middle reaches of Yangtze River during 2000-2010 with 250-m MODIS time-series data, the content includes:(1) Extracting every 8-day's water area of Poyang Lake and Dongting Lake in flood season. The results indicate that: the inundated area of the Poyang Lake in 2010 is larger than any other years. The inundated area rose up between 2000 and 2010 for the Poyang Lake, while the inundated area of the east Dongting Lake and the southwest Dongting Lake showed a clear downward trend. Within a year, the longest duration of fluctuation is up to 5-6 months during 2000-2010. The flood usually occurred from April to November, and is most frequent from June to August. Summer is a season with higher frequency of flooding.(2) Calculating the emerged depth every year. The results indicate that: the submerged depth of three Lakes (Poyang Lake, East Dongting Lake and Southwest Lake) concentrated in 0-2m, and the area of the submerged depth between 0-6m in Poyang Lake and East Dongting Lake has a downward trend, the area of the submerged depth between 0-2m in Southwest Dongting Lake rose up, but it has a downward trend between 2-6m.(3) Evaluating the loss of land use and population. The results indicate that: Paddy fields and dry land is the most serious affected land type in three lake regions, the affected area of paddy fields and dry land in Poyang Lake region rose up, the affected area of paddy fields in East Dongting Lake and Southwest Dongting Lake has a downward trend, yet the affected area of dry land has a upward trend. In Poyang Lake region, Paddy fields in Yugan County, Duchang County, Boyang County is more serious than other counties, and dry land in Boyang County, Duchang County, Jinxian County, Xingzi County is more serious than other counties; In East Dongting Lake region, Paddy fields in Huarong County, Yueyang County, Yueyang City, Yuanjiang City is more serious than other counties, and dry land in Yueyang County, Yueyang City is more serious than other counties; In Southwest Dongting Lake region, Paddy fields in Yuanjiang City, Hanshou County, Xiangyin County is more serious than other counties, and dry land in Yuanjiang City, Hanshou County is more serious than other counties; In Poyang Lake region, the number of affected population in 2010 is larger than other years, and the number of affected population in Boyang County is larger than other counties; In East Dongting Lake region, the number of affected population in 2009 is larger than other years, and the number of affected population in Yueyang City is larger than other counties; In Southwest Dongting Lake region, the number of affected population in 2005 is larger than other years, and the number of affected population in Hanshou County is larger than other counties.