This study aimed to generate a GIS-based flashflood hazard susceptibility map using the geographical information system (GIS) and frequency ratio (FR) techniques in one of the geographically isolated and disadvantaged areas (GIDAs) of the country, which is the barangay Bukang… More

This study aimed to generate a GIS-based flashflood hazard susceptibility map using the geographical information system (GIS) and frequency ratio (FR) techniques in one of the geographically isolated and disadvantaged areas (GIDAs) of the country, which is the barangay Bukang Liwayway of Kibawe, Bukidnon. There are 160 sample points conducted for flashflood inventory to calculate FR and the flashflood prediction weights values needed to generate the flashflood susceptibility map. The elevation, slope, aspect, curvature, topographic wetness index, drainage density, LULC, normalized difference vegetation index, and rainfall are the nine controlling factors that are selected. Results show that the areas exposed to flashflood with low, medium, and high-risk levels of susceptibility consist of 89.8, 4.4, and 5.7% of the total land, respectively, with 25 households exposed to high risk. The study determined the possible site for the evacuation center based on the spatial analysis resulting in the overlaying of different thematic map layers based on flashflood susceptibility factors. The study emphasizes the integration of the findings in the localized comprehensive land-use plan to realize the challenge of building a sustainable and hazard-resilient human community in Bukang Liwayway. Less

Due to threats of agricultural expansion and urbanization, riparian areas of rivers are on the brink of deterioration impacting their ecological functions such as the attenuation of flood disasters. In the urbanizing cities and municipalities of El Salvador, Gingoog and… More

Due to threats of agricultural expansion and urbanization, riparian areas of rivers are on the brink of deterioration impacting their ecological functions such as the attenuation of flood disasters. In the urbanizing cities and municipalities of El Salvador, Gingoog and Jasaan in Misamis Oriental in southern Philippines, rivers are considered critical due to its high risk to flooding occurrence. In order to implement appropriate river management practices in sustaining its ecological services, understanding the rivers’ riparian status is necessary. Hence, this study was conducted to evaluate the current status of Molugan, Solana and Odiongan rivers riparian condition. Using a check list as a guide, abiotic and biotic components of the upstream, midstream and downstream sites of the rivers were rated and evaluated. Other factors such as land use and land cover pattern, population density, stream order and slope were also taken to account in the assessment. Results showed that all rivers are still in the sub-optimal conditions implied with minimal disturbance and deterioration. However of the three rivers, Odiongan was with the least ideal general riparian habitat condition which may be attributed to the river’s larger size and accessibility to disturbance. Regardless of the good results, conscious regulation for the expansion of agricultural cultivation especially in the upstream areas of the watersheds is still recommended. In addition, appropriate land use zoning must be implemented giving emphasis on the establishment of appropriate riparian vegetation buffer widths and integrating natural conservation strategies. Less

Flood modeling studies for the purpose of forecasting, early warning, and disaster management of the local government and other disaster agencies have been done in many countries nowadays. With a similar rationale, this study aims to assess the precipitation-runoff capacity… More

Flood modeling studies for the purpose of forecasting, early warning, and disaster management of the local government and other disaster agencies have been done in many countries nowadays. With a similar rationale, this study aims to assess the precipitation-runoff capacity of the Alubijid River Basin which can put a significant number of 41,936 populations at risk to flooding. Using the 10-meter resolution SAR-DEM, the drainage system of the river basin was delineated in ArcMap 10.1 with the aid of HEC-GeoHMS. Data were collected last November 26-27, 2014 during the “Typhoon Queenie” which contributes to water level rise of 1.04 meter MSL of 86.7 mm accumulated rainfall with a peak discharge of 18.7 m3/s. The hydrologic data and generated basin model were inputted in HEC-HMS for calibration. After series of manual adjusting the river basin’s parameters, the hydrologic modeling revealed that the river basin was accepted based on the conducted model validation and performance rating. The overall statistical measures conducted obtained very good and satisfactory ratings. As a result, the basin model is accepted for water level monitoring and forecasting as it gives lead time for the preparation of evacuation of the vulnerable community to the safe sites identified by the local government unit. Less

Flood modeling is one of the recognized effective means of assessing the flood risk to people and property. In this study, the concept of flood modeling is applied in Musimusi river at Balingasag, Misamis Oriental. Using the Hydrologic Modeling System… More

Flood modeling is one of the recognized effective means of assessing the flood risk to people and property. In this study, the concept of flood modeling is applied in Musimusi river at Balingasag, Misamis Oriental. Using the Hydrologic Modeling System (HMS) and River Analysis System (RAS) of the Hydrologic Engineering Center (HEC), hydrologic and hydraulic models were developed to conduct simulations on the rainfall-runoff and flood inundation processes. Data from the Typhoon Seniang event was used as main input for the calibration of basin model and consequently validated using quantitative statistics. Further simulations on specific return periods using historical data from PAG-ASA were conducted using the calibrated model. River flow hydraulics was performed through unsteady flow analysis reconstructing the Typhoon Seniang event and constructing the 5-year, 25-year and 100-year return period scenarios, spatially illustrating flood inundations on the floodplain of Musimusi. Results of this research revealed successful simulation of flood scenarios indicating applicability of both developed HEC-HMS and HEC-RAS models. Moreover, with the integration of high resolution Digital Elevation Model (DEM), modeling is significant towards consequent development of highly precise and detailed flood hazard maps helpful especially to local governing units for the total improvement of disaster risk reduction strategies. Less

Flooding is one of the most devastating natural disasters in the Philippines, especially in Mindanao. This study aimed to generate datasets of flooding along the Gingoog River based on Geographic Information System (GIS). The method employed simulation and mapping of… More

Flooding is one of the most devastating natural disasters in the Philippines, especially in Mindanao. This study aimed to generate datasets of flooding along the Gingoog River based on Geographic Information System (GIS). The method employed simulation and mapping of flood hazards using the Hydrologic Engineering Center’s Hydrologic Modeling System (HEC-HMS) and the HEC-River Analysis System (HEC-RAS) within the GIS environment. Rainfall data on December 15, 2015, with a total amount of 20.8 mm and peak discharge of 43.49 m3s-1, were used to simulate flood hazards. The model was calibrated, and its accuracy was tested, and after which, its overall evaluation showed a satisfactory performance, implying applicability to simulate floods during extreme rainfall events. Using Light Detection and Ranging (LiDAR) data, flood maps of the three return periods were generated within HEC-RAS. Results showed that flooding extended up to 2.965 km2, 4.165 km2, and 5.040 km2 with maximum flood depths of 7.77 m, 8.12 m, and 8.49 m for 5-year, 25-year, and 100-year return periods, respectively. The model, together with the hydrologic behavior of the watershed such as the extent of flooding, is very helpful for the development and enhancement of early warning systems in the affected areas. Less