Mangrove Forest Cover Change (1947-2018) at The River Mouth Section of The Jaro Floodway, Iloilo City, Philippines

摘要

The construction of the Jaro Floodway in 2012 resulted to a rapid progradation of the shoreline in 8 years. This study examined the long- and short-term changes in area covered by mangroves at the river mouth area of this flood canal by utilizing historical maps (1947 and 1988), and Landsat images. A total of 44 Landsat images were used that covered the time periods 1998, 2000-2001, 2004, 2006, 2008, 2010-2011, 2013-2014, 2016, and 2018. Five images were used for each time period and the mangrove cover for each image was determined by using a supervised classification scheme. The set of rasters for each time period was then averaged to generate the final classification map. From 1947 to 1988, mangrove cover increased from 7.01 to 43.83 ha as a result of channel avulsion of the Jaro River due to fishpond construction at the former river mouth. However, it started to decrease until 2008 (3.42 ha) due to widespread fishpond conversion. Then, it rapidly increased to 40.05 ha in 2018. This increase is primarily attributed to the rapid expansion of the intertidal zone in the discharge area of the Jaro Floodway which is due to high sedimentation and low accommodation space.