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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

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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


CSU LiDAR 1 Conducts Planning and Workshop for Year 3

The CSU LiDAR 1 Project conducted a one-day planning and workshop for its 3rd Year of implementation last October 8, 2015 at Almont Inland Resort, Butuan City. The one-day event was centered on producing an updated workplan for the first and second year of implementation and a proposed workplan for the duration of January 2016 to March 2017.

Some of the outputs of the workshop and planning were the budgeting for the travels on the last year of implementation as well as other expenses for the continuation of the project. Furthermore, the workshop was an avenue to prepare for the documents needed for the request of the renewal of the project. At the end of the workshop, the project was able to accomplish all the expected outputs.

CSU Phil-LiDAR 1, DOST Caraga and Jabonga LGU discuss Smarter Jabonga project

Last October 16, 2015, the CSU Phil-LiDAR 1 Project was invited by the DOST Caraga Assistant Regional Director—Dr. Ricardo N. Varela—and the Local Government Unit (LGU) of Jabonga for a meeting on a possible partnership for the Smarter Jabonga Project.

Dr. Varela gave a brief background about the Smarter Jabonga Project and emphasized that the Municipality of Jabonga was the pilot area of the project. On the other hand, representatives from the Jabonga LGU, headed by Ms. Georgette Monoy of the Municipality Disaster Risk and Reduction Management Office, shared their problems on flooding and other disasters experienced by the Municipality for the past years. They also imparted the courses of actions they are making such as preparing a spot map of the houses and other establishments of the municipality, and the likes. However, in order to take the municipality to the next level in the aspect of disaster risk, reduction and management, DOST proposed that the CSU Phil-LiDAR 1 project would be part of the Smarter Jabonga. After which, presentation of the Flood Hazard Maps, Jabonga LiDAR Data and Flood EViDEns were made by Engr Arthur M. Amora, Engr. Linbert C. Cutamora and Mr. Edsel Matt O Morales, respectively.

The meeting paved way for the CSU Phil-LiDAR 1 Project, DOST Caraga and Jabonga LGU to come up with a team structure, agree on outputs as well as define the roles of each office on the implementation of the project.  Furthermore, the Smarter Jabonga Project will not only help the Municipality of Jabonga but, this will also help the CSU PhilLiDAR 1 Project in the aspect of acquisition of data per household for the Flood EViDens. A scheduled visit to the municipality to see initial outputs on the maps made by the MDRRMO will be done on October 29, 2015.

The LiDAR Team, DOST and Jabonga LGU are all looking forward to the implementation of the project after the signing of the Memorandum of Agreement.

CSU Phil-LiDAR 1 Project Leader and Chief SRS attend GeoSmart Asia 2015 in Kuala Lumpur, Malaysia, present two research papers

Engr. Meriam Makinano-Santillan, CSU Phil-LiDAR 1 Project Leader and CEIT Faculty, together with Engr. Jojene R. Santillan, CSU Phil-LiDAR 1 Chief Science Research Specialist, attended and presented research papers at the GeoSmart Asia 2015 conference held at the Putra World Trade Center, Kuala Lumpur, Malaysia from September 29-October 1, 2015. GeoSmart Asia is an annual conference and exhibition organized by Geospatial Media and Communications Sdn Bhd for the Asia Pacific geospatial community. With the theme ‘Towards the Next Big Leap,’ GeoSmart Asia delved on how geospatial has become a significant tool in the hands of businesses and nation developers, paving a smarter way to develop, progress and sustain, and the impact that this technology can create for key industries that drive the economies.

One of the many parallel activities during the 3-day conference was a technical session on Geospatial Technology in Disaster Management & Climate Change. The session gathered several researchers, scientists, decision-makers, and people from various disciplines to present and discuss research papers and projects with the aim to create awareness about the role of geospatial information in addressing various issues related to disaster management and climate change, to strengthen threat preparedness and mitigate losses. During this session, Engr. Meriam Makinano-Santillan and Engr. Jojene R. Santillan individually presented two research papers which were outcomes of the CSU Phil-LiDAR 1 project. Engr. Meriam Makinano-Santillan presented “Flood Hazard Exposure Assessment of Buildings through Combined Use of LiDAR Data and Flood Simulation Models”, while Engr. Jojene R. Santillan presented “Flood EViDEns: Near-real Time Flood Event Visualization and Damage Estimations for Geospatially-informed Decision Making in Times of Flooding”.

Engr. Meriam Makinano-Santillan doing a presentation during the ‘Geospatial Technology in Disaster Management & Climate Change’ technical session of GeoSmart Asia 2015.

Engr. Meriam Makinano-Santillan doing a presentation during the ‘Geospatial Technology in Disaster Management & Climate Change’ technical session of GeoSmart Asia 2015.

Engr. Jojene R. Santillan doing a presentation during the ‘Geospatial Technology in Disaster Management & Climate Change’ technical session of GeoSmart Asia 2015.

Engr. Jojene R. Santillan doing a presentation during the ‘Geospatial Technology in Disaster Management & Climate Change’ technical session of GeoSmart Asia 2015.

The conference brought together more than 800 participants from the geospatial community to address the evolution, changes and innovation of geospatial technology and how the same can contribute towards sustainable development of Asia Pacific.

Engr. Meriam Makinano-Santillan and Engr. Jojene R. Santillan’s participations to the conference were supported by the CSU Phil-LiDAR 1 project.

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)

Link to Full Text: View/Download


Combining geospatial data and numerical models to map and differentiate flooding extents caused by two tropical storms in the Philippines

By Meriam Makinano-Santillan, Jojene R. Santillan

ABSTRACT:

In the year 2014, heavy rains associated with tropical storms Lingling (known as Agaton in the Philippines; January 10-20, 2014) and Jangmi (locally known as Seniang; December 27, 2014 – January 1, 2014) triggered massive flooding and caused fatalities in many localities, particularly in Caraga Region in northeastern Mindanao. Based on ground data, the 10-day Agaton event brought a total rainfall of 922 mm, of which 221 mm where recorded on January 19 alone, a day before it dissipated to the southeast of the Philippines. On the other hand, the 6-day Seniang event brought a total rainfall of 356 mm, of which 259 mm where recorded on December 29 alone. 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 events by combining geospatial data from remote sensing and field surveys with numerical modelling. We focused on the Cabadabaran River Basin (CBR) and the nearby Pandanon River and Caasinan River Watersheds in Agusan del Norte, Caraga Region as our case study area. First, we developed a HEC HMS-based hydrological model of the river basin using a 10-m Synthetic Aperture Radar (SAR) Digital Elevation Model (DEM) for sub-basin delineations, land-cover maps from Landsat 8 OLI images for model parameterization, and rainfall and discharge datasets for model simulation and validation. The purpose of the HEC HMS model was to determine the volume of water coming from the various sub-basins that drains into the floodplains during the storms. The discharge hydrographs were then used as inputs into a 2-dimensional flood model to simulate the movement of flood water along the rivers and in the floodplains and to map the areas that are flooded. The 2D model was developed using a 1-m resolution LiDAR-derived Digital Terrain Model (DTM) and Landsat-derived landcover maps as its major parameters. From the numerical model simulations and output flood maps, we found that the Agaton event produced more discharge and caused wider extent of flooding than the Seniang event. This result is consistent with the fact that rainfall during Agaton was greater in volume than during Seniang. More areas were also in low and medium flood hazard levels (0.1 – 1.5 m depth) during Agaton. However, areas in high hazard levels (>1.5 m depth) appeared to be similar in both events. The results of this study showed the importance of combining geospatial data and techniques with numerical models to reconstruct and understand past flooding events. The flood simulations and maps derived from this study can be useful not only in flood hazard mapping of the project area, but also as visual aids to help people understand the differences of the impacts of different tropical storms in the occurrence of flooding.

KEYWORDS: geospatial data, remote sensing, numerical modeling, flood, tropical storms, Philippines


Publication Details/Metadata:

Paper Title: COMBINING GEOSPATIAL DATA AND NUMERICAL MODELS TO MAP AND DIFFERENTIATE FLOODING EXTENTS CAUSED BY TWO TROPICAL STORMS IN THE PHILIPPINES

Authors: Jojene R. Santillan, Meriam Makinano-Santillan

Publication Date: 2015

Conference Name/Journal/Book Title: 13th Southeast Asian Survey Congress (SEASC 2015): Expanding the Geospatial Future

Publisher: ASEAN Federation of Land Surveying and Geomatics(ASEAN FLAG), Singapore Institute of Surveyors and Valuers (SISV)

Link to Full Text: View/Download


 

Flood extent validation surveys in the river basins of Caraga region, Mindanao, Philippines and its importance in assessing the accuracy of flood hazard maps

By Arthur Amora, Jojene R. Santillan, Meriam M. Santillan, Ronald Makinano, Jennifer Marqueso, Almer Estorque, George Hussein Mordeno

ABSTRACT:

In this paper, we discuss the methods and results of our field surveys that we conducted to gather information on flood extents that are necessary for assessing the accuracy of flood hazard maps. This activity is a major part of the CSU LiDAR 1 project which we currently undertake for the purpose of generating flood hazard maps of river basins of Caraga Region in Mindanao, Philippines. CSU LiDAR 1 is one of the several projects under the “Phil-LiDAR 1: Hazard Mapping of the Philippines using LiDAR” program funded by the Philippines Council for Industry, Energy and Emerging Technology Research and Development – Department of Science and Technology (PCIEERD-DOST). For the project’s first year of implementation on 2014, it focused on the river basins of Cabadbaran, Mainit-Tubay-Asiga and Tago. The flood hazard maps of these project areas needs to be validated on the actual ground to determine its reliability and accuracy. For 2014, there were two typhoons that struck the Caraga Region in the Philippines, namely: typhoon Lingling (local name Agaton) which hit last January 2014 and typhoon Jangmi (local name Seniang) last December 2014. Necessary information on actual extent of flooding during the two typhoons where collected through conduct of GPS surveys last December 2014 – February 2015. The survey locations were based on random points generated within the flood plains of the three river basins. Information gathered during the surveys includes the estimated flood heights during the two typhoons, the corresponding date and time of occurrence and the geographic coordinates. These datasets were consolidated and statistical analyses were conducted to initially assess the effects of the nearness to the river and the slope from the river banks for the flooding that occurred on every location. Based on the results, it can be generally concluded that those areas that are near to the river are more prone to flooding compared to other areas within the river basin. Nevertheless, a relatively flat slope from the river banks to any point within the floodplain weights more effect on the proneness to flooding of an area. This was verified from the datasets from some far from the river areas but was still flooded due to its relatively flat topography from the river banks. All the data points collected were used to assess the accuracy of flood hazard maps generated by the project for the two typhoon events.

KEYWORDS: flood extent validation, Caraga Region, Mindanao, Philippines


Publication Details/Metadata:

Paper Title: FLOOD EXTENT VALIDATION SURVEYS IN THE RIVER BASINS OF CARAGA REGION, MINDANAO, PHILIPPINES AND ITS IMPORTANCE IN ASSESSING THE ACCURACY OF FLOOD HAZARD MAPS

Authors: Arthur Amora, Jojene R. Santillan, Meriam M. Santillan, Ronald Makinano, Jennifer Marqueso, Almer Estorque, George Hussein Mordeno

Publication Date: 2015

Conference Name/Journal/Book Title: 13th Southeast Asian Survey Congress (SEASC 2015): Expanding the Geospatial Future

Publisher: ASEAN Federation of Land Surveying and Geomatics (ASEAN FLAG), Singapore Institute of Surveyors and Valuers (SISV)

Link to Full Text: View/Download