Assessing the Impacts of Flooding Caused by Extreme Rainfall Events Through a Combined Geospatial and Numerical Modeling Approach

Abstract

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.

Flood Management, Characterization and Vulnerability Analysis Using an Integrated RS-GIS and 2D Hydrodynamic Modelling Approach: The Case of Deg Nullah, Pakistan

“…These flood models can simulate additional flood characteristics such as flood arrival times, flood velocities, flood duration and flood recession times [54]. Moreover, remotely sensed datasets have been extensively used with the HEC-RAS 2D model to simulate, validate and forecast flood events in different regions of the world [16,20,34,36].…”

“…RS and GIS are considered effective geospatial tools assisting in preparing the flood characteristic maps and their impacts on the environmental, social and economic aspects [15]. These geospatial tools have been extensively used to map the results of simulation models of past flood events such as flood inundation extents, flood levels and to identify the critical facilities at risk [16,17]. These tools also support developing the flood forecasting and early warning systems in flood-prone areas, which are helpful in flood hazard management and preparedness planning [18,19].…”

Exploring modern bathymetry: A comprehensive review of data acquisition devices, model accuracy, and interpolation techniques for enhanced underwater mapping

“…Regarding the uncertainty of seabed topography, Rishikeshan et al (2014) found that the IDW method performs better in flat and slope areas, while the natural neighbor (NN) method performs better in steep slopes and the whole area. Additionally, the choice of survey configuration significantly impacts the terrain's accuracy rather than the interpolation method because unevenly collecting elevation data points will affect the interpolated surface and the final generated model (Santillan et al, 2016). Zheng et al (2016) proposed an improved ANUDEM interpolation method to address voids and anomalies caused by uneven measurement coverage.…”

Beyond Flood Hazard Maps: Detailed Flood Characterization With Remote Sensing, Gis and 2d Modelling

“…These technologies have been used, either on their own or in a synergistic manner, to develop numerical flood simulation models that can aid in reconstructing past flood events for the purpose of mapping inundation levels and extents as well as to identify elements at risks (e.g., Amora et al, 2015;MakinanoSantillan et al, 2015;Santillan et al, 2016); in identifying flood-prone areas for the purpose of planning for disaster mitigation and preparedness (Asare-Kyei et al, 2015;Gashaw and Legesse, 2011;Pradhan, 2010;Samuel et al, 2014); and most especially in flood forecasting and early warning (Mioc et al, 2008;Sharif and Hashmi, 2006), among many other uses and applications. In these applications, RS has become an important source of data/information necessary to build flood models and conduct assessment of flood risks such as topography, land-cover, location of built-up areas and other elements that are at risk to flooding (e.g., roads, buildings, and bridges).…”