Comparing Combined 1D/2D and 2D Hydraulic Simulations Using High-Resolution Topographic Data: Examples from Sri Lanka—Lower Kelani River Basin

Abstract

The application of numerical models to understand the behavioural pattern of a flood is widely found in the literature. However, the selection of an appropriate hydraulic model is highly essential to conduct reliable predictions. Predicting flood discharges and inundation extents are the two most important outcomes of flood simulations to stakeholders. Precise topographical data and channel geometries along a suitable hydraulic model are required to accurately predict floods. One-dimensional (1D) hydraulic models are now replaced by two-dimensional (2D) or combined 1D/2D models for higher performances. The Hydraulic Engineering Centre’s River Analysis System (HEC-RAS) has been widely used in all three forms for predicting flood characteristics. However, comparison studies among the 1D, 2D to 1D/2D models are limited in the literature to identify the better/best approach. Therefore, this research was carried out to identify the better approach using an example case study of the Kelani River basin in Sri Lanka. Two flood events (in 2016 and 2018) were separately simulated and tested for their accuracy using observed inundations and satellite-based inundations. It was found that the combined 1D/2D HEC-RAS hydraulic model outperforms other models for the prediction of flows and inundation for both flood events. Therefore, the combined model can be concluded as the better hydraulic model to predict flood characteristics of the Kelani River basin in Sri Lanka. With more flood studies, the conclusions can be more generalized.

Advanced monitoring and numerical modelling of the stability, safety and reliability indicators of the earthen dam of Songloulou (Cameroon)

“…The modelling provides other useful information such as the vertical stresses prevailing at any point in the model. The results of the statistical study and Finite Element Modelling are in agreement with those of recent research throughout the world [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][36][37][38][39][40][41][42][43][44][45][46] for the analysis of the same phenomena. The lack data from altimetric measurements does not make it possible to have settlments or swelling on the top of the dam according to the seasons.…”

“…It should be recalled here that, the fuzzy neuron method is commonly used for the analysis of the behaviour of civil engineering and hydraulic structures. We refer to some recent works that have used this technique [38][39][40][41][42][43][44][45] with satisfactory results.…”

Rainfall Based Dynamic Flood Inundation Simulation for Kelani River Basin of Sri Lanka

“…The intensity of rainfall in the upper catchment area is the leading cause of the flood in the Kelani river areas (Perera, 2021). Very few studies consider the rainfall intensity and the Kelani River flood (Samarasinghe et al, 2022). Several studies focused on the various aspects of the Kelani river flood, mainly focusing on the impact of the river flood (Manawadu & Wijeratne, 2021).…”

Evaluation of Wanggu Watershed Carrying Capacity on Water System Indicators in Southeast Sulawesi, Indonesia

“…There are several factors that can cause flooding including climate change factors, rainfall patterns and distribution as well as an increase in the frequency and magnitude of extreme rainfall events in an area (Ariyani et al, 2022;Bian et al, 2020). Other factors that affect flooding are physiographic and geometric hydrological conditions (Kusumandari et al, 2018;Rana and Suryanarayana, 2021), topographical conditions regarding the slope of the area are related to the mapping of flood areas, especially lowland areas and basins (Samarasinghe et al, 2022), soil types related to the physical and chemical properties of the soil, especially in the soil's ability to bind water to the soil (soil permeability) (Basri et al, 2022;Karmakar et al, 2010), changes in land cover related to the needs of the human population for land resources so that it can reduce water retention capacity due to soil compaction so that it can increase surface runoff and inundation floods (Basri et al, 2022;Bian et al, 2020;Rana and Suryanarayana, 2021), as well as the factors of garbage and sediment that accumulate and block the flow of water in river channels can reduce the capacity and capacity of rivers so that water overflows out of the river inundating residential areas (Ariyani et al, 2022).…”