Open Source Flood Mapping Tools – Qgis, River Gis and Hec-Ras

Abstract

Recently, the area of free and open source geospatial data and software has experienced a significant development and progress. Since the start of geospatial open source "revolution" in the early 2000 (that began with QGIS launching), a transition from commercial software to open source alternatives has been noticed among researchers, professionals, local administrations, etc. This study focuses on using available open source solutions in order to obtain useful information regarding the delineation of flood hazard and flood risk areas. QGIS, a free and open-source geographic information system software was used for spatial data visualization, editing and analysis. River GIS is a QGIS plugin that allows the creation of 1D or 2D geometric flow models using the QGIS environment. A 1D flow model and HEC-RAS software was used to estimate the hydraulics of water flow, delineating the vulnerable areas. Useful information about flood hazard and risk exposure was obtained, the methodology used proved efficient considering the time, cost and the quality of the output. The results managed to capture and delimitate the flood prone areas and the amount of social damages in term of affected persons. Taking into consideration the cost related issues, this methodology can be applied easily by all the interested parties (local communities, local authorities, scientists, responsible persons with flood mitigation) in the development of local, regional or national flood management plans.

Flood Modeling of Imus River Basin, Cavite, Philippines at Different Climate and Land Cover Change Scenarios

“…Using the generated synthetic hydrographs for the different return periods at normal conditions and based on PAGASA climate projections [6, 30], hydraulic modeling for the river basin was done through 2D unsteady ow analysis in HEC-RAS. The ood model showed a simulated water level at each crosssection for every time step and ood simulation created [31,32]. The resulting model was used in determining the ooded areas caused by the discharge of water from the upstream of the Imus River Basin.…”