Category Archives: Publication

Assessing the impacts of flooding caused by extreme rainfall events through a combined geospatial and numerical modeling approach

By Jojene R. Santillan, Arthur M. Amora, Meriam Makinano-Santillan, Jennifer T. Marqueso, Linbert C. Cutamora, Jesiree L. Serviano, Ronald M. Makinano

ABSTRACT:

In this paper, we present a combined geospatial and two dimensional (2D) flood modeling approach to assess the impacts of flooding due to extreme rainfall events. We developed and implemented this approach to the Tago River Basin in the province of Surigao del Sur in Mindanao, Philippines, an area which suffered great damage due to flooding caused by Tropical Storms Lingling and Jangmi in the year 2014. The geospatial component of the approach involves extraction of several layers of information such as detailed topography/terrain, man-made features (buildings, roads, bridges) from 1-m spatial resolution LiDAR Digital Surface and Terrain Models (DTM/DSMs), and recent land-cover from Landsat 7 ETM+ and Landsat 8 OLI images. We then used these layers as inputs in developing a Hydrologic Engineering Center Hydrologic Modeling System (HEC HMS)-based hydrologic model, and a hydraulic model based on the 2D module of the latest version of HEC River Analysis System (RAS) to dynamically simulate and map the depth and extent of flooding due to extreme rainfall events. The extreme rainfall events used in the simulation represent 6 hypothetical rainfall events with return periods of 2, 5, 10, 25, 50, and 100 years. For each event, maximum flood depth maps were generated from the simulations, and these maps were further transformed into hazard maps by categorizing the flood depth into low, medium and high hazard levels. Using both the flood hazard maps and the layers of information extracted from remotely-sensed datasets in spatial overlay analysis, we were then able to estimate and assess the impacts of these flooding events to buildings, roads, bridges and landcover. Results of the assessments revealed increase in number of buildings, roads and bridges; and increase in areas of land-cover exposed to various flood hazards as rainfall events become more extreme. The wealth of information generated from the flood impact assessment using the approach can be very useful to the local government units and the concerned communities within Tago River Basin as an aid in determining in an advance manner all those infrastructures (buildings, roads and bridges) and land-cover that can be affected by different extreme rainfall event flood scenarios.

KEYWORDS:  Extreme rainfall, Flooding, Impact assessment, 2D Flood modeling, LiDAR, Landsat


Publication Details/Metadata:

Paper Title: AASSESSING THE IMPACTS OF FLOODING CAUSED BY EXTREME RAINFALL EVENTS THROUGH A COMBINED GEOSPATIAL AND NUMERICAL MODELING APPROACH

Authors: Jojene R. Santillan, Arthur M. Amora, Meriam Makinano-Santillan, Jennifer T. Marqueso, Linbert C. Cutamora, Jesiree L. Serviano, Ronald M. Makinano

Publication Date: 2016

Conference Name/Journal/Book Title: ISPRS – International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences

Volume: XLI-B8

Pages: 1271-1278

Publisher: International Society for Photogrammetry and Remote Sensing (ISPRS), Copernicus GmbH

Link to Full Text: View/Download from: ISPRS Website or CCGeo.Info Website

Academe-local government partnership towards effective application of geospatial technologies for smarter flood disaster management at the local level: an example from Mindanao, Philippines

By Meriam Makinano-Santillan, Jojene R. Santillan, Edsel Matt O. Morales, Lorie Cris S. Asube, Arthur M. Amora, Linbert C. Cutamora, Ronald. M. Makinano

ABSTRACT:

In this paper, we discuss how an academe-local government partnership can lead the way for the effective use of geospatial technologies for smarter and geospatially-informed decision making before, during, and after a flood disaster. In Jabonga municipality, in the province of Agusan del Norte, in Mindanao, Philippines, two significant flooding events occurred in the year 2014 which were caused by overflowing water bodies due to continuous heavy rains. These flood events inundated populated areas, caused massive evacuation, made roads un-passable, and greatly damaged sources of incomes such as croplands and other agricultural areas. The partnership between Caraga State University and the local government of Jabonga attempts to improve localized flood disaster management through the development of web-based Near-real Time Flood Event Visualization and Damage Estimations (Flood EViDEns) application. Flood EViDENs utilizes LiDAR-derived elevation and information products as well as other elevation datasets, water level records by monitoring stations, flood simulation models, flood hazard maps, and socio-economic datasets (population, household information, etc.), in order to visualize in near-real time the current and future extent of flooding, to disseminate early warnings, and to provide maps and statistics of areas and communities affected and to be affected by flooding. The development of Flood EViDEns as the main product of the partnership is an important application of geospatial technologies that will allow smarter and geospatially-informed decision making before, during, and after a flood disaster in Jabonga.

KEYWORDS:  Geospatial technology, Flood, Disaster management, Academe-local government partnership, Mindanao, Philippines


Publication Details/Metadata:

Paper Title: ACADEME-LOCAL GOVERNMENT PARTNERSHIP TOWARDS EFFECTIVE APPLICATION OF GEOSPATIAL TECHNOLOGIES FOR SMARTER FLOOD DISASTER MANAGEMENT AT THE LOCAL LEVEL: AN EXAMPLE FROM MINDANAO, PHILIPPINES

Authors: Meriam Makinano-Santillan, Jojene R. Santillan, Edsel Matt O. Morales, Lorie Cris S. Asube, Arthur M. Amora, Linbert C. Cutamora, Ronald. M. Makinano

Publication Date: 2016

Conference Name/Journal/Book Title: ISPRS – International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences

Volume: XLI-B8

Pages: 109-115

Publisher: International Society for Photogrammetry and Remote Sensing (ISPRS), Copernicus GmbH

Link to Full Text: View/Download from: ISPRS Website or CCGeo.Info Website

Vertical accuracy assessment of 30-m resolution ALOS, ASTER, and SRTM global DEMs over northeastern Mindanao, Philippines

By Jojene R. Santillan, Meriam Makinano-Santillan

ABSTRACT:

The ALOS World 3D – 30 m (AW3D30), ASTER Global DEM Version 2 (GDEM2), and SRTM-30 m are Digital Elevation Models (DEMs) that have been made available to the general public free of charge. An important feature of these DEMs is their unprecedented horizontal resolution of 30-m and almost global coverage. The very recent release of these DEMs, particularly AW3D30 and SRTM- 30 m, calls for opportunities for the conduct of localized assessment of the DEM’s quality and accuracy to verify their suitability for a wide range of applications in hydrology, geomorphology, archaelogy, and many others. In this study, we conducted a vertical accuracy assessment of these DEMs by comparing the elevation of 274 control points scattered over various sites in northeastern Mindanao, Philippines. The elevations of these control points (referred to the Mean Sea Level, MSL) were obtained through 3rd order differential levelling using a high precision digital level, and their horizontal positions measured using a global positioning system (GPS) receiver. These control points are representative of five (5) land-cover classes namely brushland (45 points), built-up (32), cultivated areas (97), dense vegetation (74), and grassland (26). Results showed that AW3D30 has the lowest Root Mean Square Error (RMSE) of 5.68 m, followed by SRTM-30 m (RMSE = 8.28 m), and ASTER GDEM2 (RMSE = 11.98 m). While all the three DEMs overestimated the true ground elevations, the mean and standard deviations of the differences in elevations were found to be lower in AW3D30 compared to SRTM-30 m and ASTER GDEM2. The superiority of AW3D30 over the other two DEMS was also found to be consistent even under different landcover types, with AW3D30’s RMSEs ranging from 4.29 m (built-up) to 6.75 m (dense vegetation). For SRTM-30 m, the RMSE ranges from 5.91 m (built-up) to 10.42 m (brushland); for ASTER GDEM2, the RMSE ranges from 9.27 m (brushland) to 14.88 m (dense vegetation). The results of the vertical accuracy assessment suggest that the AW3D30 is more accurate than SRTM-30 m and ASTER GDEM2, at least for the areas considered in this study. On the other hand, the tendencies of the three DEMs to overestimate true ground elevation can be considered an important finding that users of the DEMs in the Philippines should be aware of, and must be considered into decisions regarding use of these data products in various applications.

KEYWORDS:  AW3D30, ASTER GDEM2, SRTM-30m, Digital Elevation Model, Accuracy Assessment, Philippines


Publication Details/Metadata:

Paper Title: VERTICAL ACCURACY ASSESSMENT OF 30-M RESOLUTION ALOS, ASTER, AND SRTM GLOBAL DEMS OVER NORTHEASTERN MINDANAO, PHILIPPINES

Authors: Jojene R. Santillan, Meriam Makinano-Santillan

Publication Date: 2016

Conference Name/Journal/Book Title: ISPRS – International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences

Volume: XLI-B4

Pages: 149-156

Publisher: International Society of Photogrammetry and Remote Sensing (ISPRS)

Link to Full Text: View/Download from: ISPRS Website or CCGeo.Info Website

FLOOD EViDENS: a web-based application for near-real time flood event visualization and damage estimations

By Jojene R. Santillan, Edsel Matt O. Morales, Meriam M. Santillan

ABSTRACT:

The Web-based Near-real Time Flood Event Visualization and Damage Estimations (Flood EViDEns) is an online geo-visualization application developed through the Phil-LiDAR 1 project of Caraga State University. The application is targeted to be utilized by the Local Government Units (LGUs) and communities in the Caraga Region, Mindanao, Philippines to assist them in geospatially informed decision making in times of flood disasters. The application is an amalgamation of web mapping technology, various geospatial datasets including LiDAR-derived elevation and information products, hydro-meteorological data, and flood simulation models to visualize in near-real time the current and possible future extent of flooding and its associated damages to infrastructures. The Flood EViDEns application facilitates the release and utilization of this near-real time flood-related information through a user-friendly front end interface consisting of web map and tables. The application’s back-end consists of computers running flood simulation models and geospatial analysis to dynamically produce (in an automated manner) current and future flood extents, and tabulated information on the structures affected by flooding including hazard types. These outputs are forwarded into a PostgreSQL/PostGIS spatial database where it is accessed by the front end interface for web visualization. The information provided by Flood EViDEns is very important especially to the LGUs and the community as it can increase awareness and responsiveness of the public to the impending flood disaster. Providing this kind of information during a heavy rainfall event is useful as it could assist in preparation for evacuation, in easily identifying areas that need immediate action, in identifying areas that should be avoided, and in estimating the severity of damage to people and infrastructure as flooding progresses.

KEYWORDS: Flood, hazard, visualization, decision support, disaster preparedness


Publication Details/Metadata:

Paper Title: FLOOD EViDENS: A WEB-BASED APPLICATION FOR NEAR-REAL TIME FLOOD EVENT VISUALIZATION AND DAMAGE ESTIMATIONS

Authors: Jojene R. Santillan, Edsel Matt O. Morales, Meriam M. Santillan

Publication Date: 2015

Conference Name/Journal/Book Title: 36th Asian Conference on Remote Sensing 2015 (ACRS 2015): Fostering Resilient Growth in Asia

Volume: 4

Pages: 2655-2664

Publisher: Asian Association on Remote Sensing

Link to Full Text: View/Download


Evaluating the impacts of landcover change to runoff potential of Tubay river basin through the analysis of multitemporal Landsat images

By Sherwin P. Pulido, Meriam Makinano-Santillan, Jojene R. Santillan

ABSTRACT:

When rain hits saturated or impervious ground it begins to flow overland downhill. Based on observations, changes to land cover can influence the velocity of overland flow. Land use patterns, including increases in impermeable surfaces and construction near riparian zones, affect flow patterns. Increased impervious surface in the areas can reduce the time of runoff and increase the peak discharges of stream flow, resulting in large and more frequent incidents of flooding. Land use within the Mainit-Tubay watershed has undergone changes in the past years. This watershed is located in Caraga region in Northeastern part of Mindanao and has a total area of 994.7292 sq. km. The population has increased and with it, an increase in deforestation and impermeable surfaces. This study evaluated the effects of land cover change to the potential runoff that occurred to the watershed during a rainfall event. The researchers generated land cover maps through the analyses of Landsat images acquired in the years 1995, 2001 and 2014. With this, land cover change was analyzed using remote sensing and GIS techniques. The changes detected were further analyzed to relate it to the changes in surface runoff. Rainfall data during Typhoon Agaton and Typhoon Seniang were utilized to generate runoff depth map. Soil data and curve numbers were added to the land cover maps to generate the runoff volume within the area. Then runoff change was determined. The generated land cover change maps and the runoff change were analyze and evaluated to know the potential effects of runoff change as effect of the changes in land cover. As computed, total runoff volume accumulated in year 2001 was reduced by about 90,894 cu. m. compared during the year 1995. However, a significant increase of runoff volume was detected in the year 2014, in which about 384,000 cu. m. difference from the volume in year 2001 was calculated. This change resulted from the increase in built up, barren and water area which has high runoff potential and in the decrease of shrubs and trees area which has low runoff potential.

KEYWORDS: Surface runoff, land cover, watershed, Landsat


Publication Details/Metadata:

Paper Title: EVALUATING THE IMPACTS OF LANDCOVER CHANGE TO RUNOFF POTENTIAL OF TUBAY RIVER BASIN THROUGH THE ANALYSIS OF MULTITEMPORAL LANDSAT IMAGES

Authors: Sherwin P. Pulido, Meriam Makinano-Santillan, Jojene R. Santillan

Publication Date: 2015

Conference Name/Journal/Book Title: 36th Asian Conference on Remote Sensing 2015 (ACRS 2015): Fostering Resilient Growth in Asia

Volume: 5

Pages: 3435-3442

Publisher: Asian Association on Remote Sensing

Link to Full Text: View/Download


Understanding the impacts of storm induced flooding at the local level through flood modelling with SAR DEM, Lidar DTM & DSM, HEC HMS and HEC RAS

By Amor L. Gingo, Meriam Makinano-Santillan, Jojene R. Santillan

ABSTRACT:

Flooding has long been considered to be one of the deadliest natural disasters. In large river basins, flooding can submerge a whole city and cause irreparable damage to human lives and properties. The same can be said at the local level where a small creek can submerge a whole barangay, especially if the creek receives large volume of water from the upstream that are beyond its capacity. In this paper, we analyzed the physical impacts of flooding caused by the overflowing of Lemon Creek to the surrounding local community in Butuan City, Philippines. The physical impacts were analyzed in terms of flood depth and inundation extent during heavy rainfall caused by tropical storms/typhoons. In this study, we focused on the flooding impacts of Tropical Storm Agaton (January2014) and Seniang (December 2014). First, we developed a HEC HMS based hydrological model of the Lemon Creek watershed to determine the volume of water flowing into the creek during the storm durations. The HEC HMS model was developed using a 10m SAR DEM for watershed and stream delineation and a Landsat 8 OLI image for land cover parameter derivation. Discharge measurements were used to calibrate and validate the model. Then, we developed a HEC RAS model to simulate the overflowing of the creek during the storm events, with the HEC HMS simulated discharge hydrographs as inputs. A 1m resolution LiDAR Digital Terrain Model (DTM) acquired before the storms was used in generating the geometrical parameters of the HEC RAS model, and as input in the flood depth and inundation mapping. Results of the integrated HEC HMS HEC RAS flood modeling showed the extent of flooding during Agaton and Seniang. Using location of structures digitized from a LiDAR Digital Surface Model (DSM), the severity of the impacts of flooding to the local community was determined by counting the number of structures inundated during the onslaught of the tropical storms.

KEYWORDS: localized flooding, impacts, LiDAR, HEC HMS, HEC RAS


Publication Details/Metadata:

Paper Title: UNDERSTANDING THE IMPACTS OF STORM INDUCED FLOODING AT THE LOCAL LEVEL THROUGH FLOOD MODELLING WITH SAR DEM, LIDAR DTM & DSM, HEC HMS AND HEC RAS

Authors: Amor L. Gingo, Meriam Makinano-Santillan, Jojene R. Santillan

Publication Date: 2015

Conference Name/Journal/Book Title: 36th Asian Conference on Remote Sensing 2015 (ACRS 2015): Fostering Resilient Growth in Asia

Volume: 5

Pages: 3443-3451

Publisher: Asian Association on Remote Sensing

Link to Full Text: View/Download


Near-real time rainfall monitoring in the Caraga region, Mindanao, Philippines using openlayers api and javascript

By Edsel Matt O. Morales, Jojene R. Santillan, Meriam Makinano-Santillan

ABSTRACT:

We developed an online tool for near-real time monitoring of rainfall intensity and accumulated rainfall in various localities in the Caraga Region, Mindanao, Philippines. The web map interface was built using Openlayers API where the locations of all rain gauge stations installed by ASTI DOST are plotted. For each station, a JavaScript is used to extract and analyze 24-hour rainfall data from the ASTI DOST. Based on extracted data, the current rainfall intensity at each rain gauge location is plotted on the web map according to a color scheme that signifies no rainfall, light, moderate, heavy, intense, and torrential rainfall intensities. Clicking on the points of a rain gauge will also show a graph of the rainfall intensities and accumulated rainfall in the last 24 hours. The application is available at http://rainmonitoring.csulidar1.ccgeo.info which can be utilized by Local Government Units (LGUs) and residents of Caraga Region, for rapid rainfall monitoring and as a tool for flood disaster preparedness.

KEYWORDS: rainfall monitoring, Caraga Region, flood early warning, OpenLayers API, Javascript


Publication Details/Metadata:

Paper Title: NEAR-REAL TIME RAINFALL MONITORING IN THE CARAGA REGION, MINDANAO, PHILIPPINES USING OPENLAYERS API AND JAVASCRIPT

Authors: Edsel Matt O. Morales, Jojene R. Santillan, Meriam Makinano-Santillan

Publication Date: 2015

Conference Name/Journal/Book Title: 36th Asian Conference on Remote Sensing 2015 (ACRS 2015): Fostering Resilient Growth in Asia

Volume: 4

Pages: 2677-2682

Publisher: Asian Association on Remote Sensing

Link to Full Text: View/Download


Flood hazard exposure assessment of buildings through combined use of Lidar data and flood simulation models

By Meriam Makinano-Santillan, Jojene R. Santillan, Linbert C. Cutamora, Jesiree L. Serviano

ABSTRACT:

Determining the types and locations of buildings that are exposed to various flood hazards is important in flood disaster preparedness, risk assessment, and mitigation. In most cases, the availability of a 3D building database where each building is attributed in terms of name, type (e.g., residential, commercial, government, educational, etc.), and height (among many other attributes) makes the required analysis fast, efficient and informative. In this work, we conducted flood hazard exposure assessment of buildings in Cabadbaran River Basin, Mindanao, Philippines through combined use of LiDAR data and flood simulation models. First, we generated a 3D GIS database of buildings through analysis of various datasets that include 1-m resolution LiDAR Digital Surface Models (DSM) and Digital Terrain Model (DTM), high resolution images in Google Earth, and free online web maps such as Wikimapia. Building footprints were manually digitized from LiDAR DSMs and saved as GIS Shapefiles. The average of the base elevations and top elevations for each footprint were then extracted from the DTM and DSM, respectively, and used to compute for the building heights. Information on the name and type of the buildings was obtained by using Google Earth, Google Map, and Wikimapia as references. The generated 3D building database was used later on in the flood hazard exposure assessment through GIS overlay analysis. Prior to this assessment, we first developed a flood model of the river basin using a combination of HEC HMS hydrological model and HEC RAS hydraulic model. The flood model was used generate flood hazard maps that are representative of maximum flooding due to rainfall events of varying return periods (2-, 5-, 10-, 25-, 50-, and 100-year return periods). With these inputs (3D building database and flood hazard maps), we conducted overlay analysis to identify which buildings are exposed to various levels of flood hazards (e.g., low, medium, high). In addition to this, we also characterized the degree of flood exposure of buildings by comparing their heights with the simulated flood depths. The results of this study consist of a series of maps showing buildings exposed to various flood depth and hazard levels that can be utilized by Local Government Units in their flood disaster risk reduction and management strategies.

KEYWORDS: Flood hazard, exposure, buildings, assessment, LiDAR, flood simulation, Mindanao; Philippines


Publication Details/Metadata:

Paper Title: Flood Hazard Exposure Assessment of Buildings Through Combined Use of LiDAR Data and Flood Simulation Models

Authors: Meriam Makinano-Santillan, Jojene R. Santillan, Linbert C. Cutamora, Jesiree L. Serviano

Publication Date: 2015

Conference Name/Journal/Book Title: GeoSmart Asia 2015: Towards the Next Big Leap, September 29-October 1, Putra World Trade Center (PWTC), Kuala Lumpur, Malaysia

Publisher: Geospatial Media and Communications

Link to Full Text: View/Download


Flood EViDEns: near-real time flood event visualization and damage estimations for geospatially-informed decision making in times of flooding

By Jojene R. Santillan, Meriam Makinano-Santillan, Edsel Matt Morales

ABSTRACT:

The Web-based Near-real Time Flood Event Visualization and Damage Estimations (Flood EViDEns) is an online geo-visualization application developed through the Phil-LiDAR 1 project of Caraga State University. The application is targeted to be utilized by the Local Government Units (LGUs) and communities in the Caraga Region, Mindanao, Philippines to assist them in geospatially informed decision making in times of flood disasters. The application is an amalgamation of web mapping technology, various geospatial datasets including LiDAR-derived elevation and information products, hydro-meteorological data, and flood simulation models to visualize in near-real time the current and possible future extent of flooding and its associated damages to infrastructures. The Flood EViDEns application facilitates the release and utilization of this near-real time flood-related information through a user-friendly front end interface consisting of web map, tables and charts. The application’s back-end consists of computers running flood simulation models and geospatial analysis to dynamically produce (in an automated manner) water level forecasts, current and future flood extents, and tabulated information on the structures affected by flooding including hazard types. These outputs are forwarded into a PostgreSQL/PostGIS spatial database where it is accessed by the front end interface for web visualization. The information provided by Flood EViDEns is very important especially to the LGUs and the community as it can increase awareness and responsiveness of the public to the impending flood disaster. Providing this kind of information during a heavy rainfall event is useful as it could assist in preparation for evacuation, in easily identifying areas that need immediate action, in identifying areas that should be avoided, and in estimating the severity of damage to people and infrastructure as flooding progresses.

KEYWORDS: Flood event, visualization, damage estimation, geospatially-informed decision making


Publication Details/Metadata:

Paper Title: Flood EViDEns: Near-real Time Flood Event Visualization and Damage Estimations for Geospatially-informed Decision Making in Times of Flooding

Authors: Jojene R. Santillan, Meriam Makinano-Santillan, Edsel Matt Morales

Publication Date: 2015

Conference Name/Journal/Book Title: GeoSmart Asia 2015: Towards the Next Big Leap, September 29-October 1, Putra World Trade Center (PWTC), Kuala Lumpur, Malaysia

Publisher: Geospatial Media and Communications

Link to Full Text: View/Download


Numerical model simulations and geospatial analysis of flooding impacts of Agaton and Seniang in Cabadbaran river basin, Mindanao, Philippines

By Jojene R. Santillan, Meriam Makinano-Santillan

ABSTRACT:

In 2014, heavy to torrential rains brought by tropical storms Agaton and Seniang triggered massive flooding and caused fatalities particularly in Caraga Region in northeastern Mindanao. To better understand and differentiate the impacts of heavy rains brought by these tropical storms to the extent of flooding, we reconstructed the two flooding eventsthrough numerical model simulations, and evaluated the differences through geospatial analysis.We focused on the Cabadbaran River Basin (CBR) and adjoining watersheds in Agusan del Norte, Caraga Region as our case study area. Results of the study havesome practical implications toclimate changeimpact and mitigation studies on the aspect that studying how the current weather and climate scenarios are affecting us (e.g., in terms of flooding) can help us understand and make necessary preparations for a future weather or climate scenario.

KEYWORDS: Tropical Storms, Flooding, Impacts, Numerical Simulation, Analysis


Publication Details/Metadata:

Paper Title: NUMERICAL MODEL SIMULATIONS AND GEOSPATIAL ANALYSIS OF FLOODING IMPACTS OF AGATON AND SENIANG IN CABADBARAN RIVER BASIN, MINDANAO, PHILIPPINES

Authors: Jojene R. Santillan, Meriam Makinano-Santillan

Publication Date: 2015

Conference Name/Journal/Book Title: 4th National Climate Conference: Local Adaptation Actions with Mitigation Co-Benefits

Publisher: National Academy of Science and Technology, Philippines (NAST PHL)

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