Vol: 1 Issue: 1
Flood Inundation Mapping of Calabar River Using Hec-Ras and QGIS
Ibiang Ebri Ibiang, Hycienth Uka Edubi
1. INTRODUCTION
Floods are recurrent natural disasters with significant effects on human populations and the environment. Flooding has had a profound and wide-ranging effect on communities, ecosystems, and the economy in the Nigerian state of Cross River. Using both local and worldwide viewpoints, this section gives a general overview of floods and their effects on the region. A naturally occurring hydrological phenomenon, floods are defined as the flooding of normally dry areas. Numerous things can cause them, such as excessive rain, snowmelt, storms, river overflows, and coastal locations [1]. Floods are a major obstacle to sustainable development in areas like Cross River State, where a complicated network of rivers and climate conditions are prevalent. With so many rivers, notably the Calabar River, Cross River State is especially prone to floods [2]. Floods in the state have an effect that goes beyond only immediate property destruction; they also interfere with livelihoods, infrastructure, and agriculture, which feeds a vicious cycle of social and economic problems [3].
HEC-RAS, the Hydrologic Engineering Center's River Analysis System is a crucial instrument in hydraulic modelling for risk assessment and flood mapping in the Calabar River region. This specialist program was developed by the U.S. Army Corps of Engineers [4] and enables thorough study of river systems under various situations. Its features, which include sediment transport modelling, one-dimensional steady and unsteady flow, and water quality analysis, make it adaptable and ideal for intricate situations such as flood mapping. With its tools for modelling infrastructure like Flood Inundations, culverts, bridges, and channel alterations, HEC-RAS allows for a comprehensive knowledge of river dynamics. The program uses crucial data, such as topography, bathymetric, and cross-sectional information, to generate accurate hydraulic models. Flood mapping is made possible by HEC-RAS, which simulates how rivers react to various flow circumstances. This allows for the prediction of inundation extents, water velocities, and depths during flood occurrences. Because of the integration of data from many sources, such as GIS and cross-sectional surveys, HEC-RAS can provide crucial insights for the region's flood risk assessment.
Flood analysis may be approached more effectively with the combined use of HEC-RAS and QGIS, two crucial tools for flood mapping. The U.S. Army Corps of Engineers created HEC-RAS, a hydraulic modelling tool that is used to properly simulate the characteristics of flood occurrences as well as model river systems, bridges, culverts, and Flood Inundations. However, data integration, visualization, and analysis are areas where QGIS, an adaptable open-source GIS program, shines [5] These two instruments work together to offer a holistic approach to comprehending and controlling flood occurrences in the Calabar River basin.
Floodplain mapping in Pakistan's Kabul River, providing a valuable tool for policymakers and urban planners in the region to identify and mitigate flood risks. Using the model, the study generates floodplain maps that delineate vulnerable areas, enabling informed decision-making for flood preparedness and disaster prevention. Radar Topography Mission digital elevation model and flood frequency analysis techniques was used to calculate extreme flows, revealing a significant 400% increase in flood risk, particularly in agricultural areas [6].
The application of HEC-RAS and ArcGIS for floodplain mapping in Segamat Town, Malaysia, emphasizing a risk-based approach to flood mitigation was carried out using Interferometric Synthetic Aperture Radar (IFSAR) data to analyze flood frequency and employed five distribution models to calculate extreme flows [7]. The Generalized Pareto distribution was found to best represent the flood characteristics of the Segamat River. Peak flood data from frequency analysis was used as input for the HEC-RAS model to determine corresponding flood levels, and ArcGIS was used to create floodplain maps for different return periods.
Comprehensive approach to flood modelling on a regional scale can be developed by combining Geographic Information Systems (GIS) with a rainfall-runoff model (HEC-HMS) and a hydrologic model (HEC-RAS) [8]. HEC-RAS produces Flood inundation maps that highlight areas at risk and delineate regions prone to flooding. It emphasizes 2D modelling of flood problems and demonstrates the significance of employing flood risk reduction measures to prepare for and manage future flood events.
This research aims to generate a flood inundation map of the Calabar River using QGIS and HEC-RAS. The research helps to enhance disaster preparedness, promote climate resilience, and engage local communities in flood mapping and management efforts.