[U-05] Geospatial Applications for Natural Resources, Environment and Agriculture

[U05-07] Sediment Erosion and Deposition Patterns in the Itogon Sub-catchment using CAESAR-Lisflood Model

*Francis Ian Pabillar Gonzalvo¹、Decibel Faustino-Eslava¹、Jenielyn Tuando Padrones¹、Juan Miguel Guotana¹、Loucel Cui¹、Eduardo Calzeta¹、Cristino Tiburan, Jr.¹、Tomas Reyes, Jr.¹、Kennethjer Alejo¹、Ylam Shalev Matba¹、Kim Bryan Cabrera¹、Laura Quick²、Richard Williams²、Thomas Coulthard³、Emma Biles⁴ (1.University of the Philippines Los Banos、2.University of Glasgow, United Kingdom、3.University of Hull, United Kingdom、4.Liverpool John Moores University, United Kingdom)

キーワード：Tropical watershed, Mining, Sediment erosion and deposition, CAESAR-Lisflood Model, Project PAMANA

Watersheds in tropical regions tend to be more vulnerable to river erosion and sedimentation than those in temperate regions due to more extremes in climate which can be experienced both seasonally and sporadically throughout the year. In addition, mineral-rich catchments in the tropics, such as those in the Philippines, experience exacerbated river erosion, surface and subsurface disturbance, and complete changes to river network landscapes from unsustainable mining operations and exploration activities. Project PAMANA or the “Philippine Mining at the National to Catchment Scale: From Legacy Impacts to Sustainable Futures” aims to achieve the sustainable management of mining activities in mineralized watersheds in the Philippines. One of the project objectives is to identify and understand the changes in the landscape of the rivers and streams in the Itogon sub-catchment of the Agnor River Watershed, one of the 18 critical watersheds in the Philippines, by investigating patterns of sediment erosion and deposition. This study area also contained the largest and oldest mining operations in the country along with many smaller-scale operations. The Digital Elevation Model (DEM) and data from a ten-year rainfall record from January 2012 to December 2022 were processed and simulated using the CAESAR-Lisflood model. The grain size data was also collected and incorporated into the model to determine the sediment size distribution within the river network. Results showed noticeable changes in the DEM, which captured the widening of the riverbanks due to erosion and deposition. Additionally, coarser sediments were mostly deposited in the eastern part of the sub-catchment where the main outlet is located. The outputs are in the form of maps and are processed by using the ArcGIS system software. Results were validated through ground truthing in the field campaign conducted. The obtained values also provided an overview of the sediment erosion and deposition patterns including the relationship between the size of the sediment and the discharge of the river in the Itogon sub-catchment.