The Effect of Incorporation of Embankment Information for Flood Simulation of the Gin River, Sri Lanka

Jayapadma, J.M.M.U.; Souma, Kazuyoshi; Ishidaira, Hiroshi; Magome, Jun; Wickramaarachchi, T. N.

doi:10.20965/jdr.2022.p0475

Cited by 6 publications

(9 citation statements)

References 50 publications

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“…NSE varies from −∞ to 1, where a value of 1 indicates that the simulated hydrographs agree perfectly with the observed hydrographs. The optimized parameters of river and slope obtained from previous RRI model applications (Sayama et al, 2012;Jayapadma et al, 2022) are summarized in Tables 1 and 2. A comparison of simulated and observed hydrographs based on daily APHRODITE rainfall, daily evaporation from GLDAS and the 1992 land-use map at the two gauging stations is shown in Figure 2 for the historical period of 1980-2000.…”

Section: Model and Data Usedmentioning

confidence: 99%

Projection of climate change effects on flood inundation in the Gin River basin, Sri Lanka

Jayapadma,

Souma,

Ishidaira

et al. 2024

Proc. IAHS

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Abstract. Human-induced climate change has altered the frequency and severity of heavy precipitation, droughts, and floods worldwide. Sri Lanka, a developing country in the Indian Ocean, has suffered frequent floods, affecting over 64 % of the population in the past decade. The Gin River, the primary drinking water source of the densely populated Galle district with over 1 million residents, faces recurrent flood disasters. Therefore, this study employed a multi-model ensemble to simultaneously simulate the impact of climate change on both river flow and inundation extent in the frequently flooded Gin River basin located in humid tropical monsoon region. Bias-corrected climate projections of an ensemble of five General Circulation Models (GCMs) from the Coupled Model Inter-comparison Project Phase 5 (CMIP5) under Representative Concentration Pathway (RCP) 4.5 emission scenario were used to project future river flow and flood inundation in the Gin River basin, Sri Lanka. The validated Rainfall–Runoff–Inundation (RRI) model projected a 5 % increase in high flows (flows exceeding a 5 % probability of exceedance (<Q5)) at the downstream (Baddegama) gauging station and a 16 % increase at the upstream (Thawalma) gauging station in the future (2040–2060) in comparison to the past (1980–2000), which can be attributed to the elevated rainfall projected during the two monsoon seasons (southwest monsoon (May–September) and northeast monsoon (December–February)) by the GCM ensemble. In addition to the projected changes in high flows revealed by the RRI simulations, the model also yielded critical information about the expansion of annual maximum inundated extent in the basin by 3.5 % that will aid flood risk projection and sustainable management in the basin.

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Section: Model and Data Usedmentioning

confidence: 99%

Projection of climate change effects on flood inundation in the Gin River basin, Sri Lanka

Jayapadma,

Souma,

Ishidaira

et al. 2024

Proc. IAHS

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“…Hydrological Model This study applied the Nedbør-Afstrømings-Model (NAM), a lumped conceptual module built in MIKE 11, to simulate rainfall-runoff in a continuous mode. The model has been successfully applied by previous researchers for hydrological investigations in many catchments including the catchments in Sri Lanka: rainfall-runoff simulations [15], [16], [17], model performance evaluation studies [18], land use change impact assessments on flood formations [19], and runoff simulations in un-gauged catchments [5], [6].…”

Section: 2mentioning

confidence: 99%

Temporal Transferability of Calibrated Hydrological Model Parameters: A Case Study of Gin Catchment, Sri Lanka

Wickramaarachchi

Gunasekara

2023

Engineer

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Lack of observed data for model calibration hinders the application of hydrological models in many poorly-gauged catchments, particularly in the humid tropical region. Despite much less attention given, it is vital to assess transferability of calibrated parameters in order to apply hydrological models in such catchments to assist their water resources planning and management activities. Thus, this study investigated temporal transferability of a lumped conceptual hydrological model's (MIKE 11 NAM) calibrated model parameters for rainfall-runoff simulations in two different time periods beyond its calibration period. Study area was selected as Gin catchment located in the humid tropical region. MIKE 11 NAM model was calibrated for the period 1995-1998 [Nash Sutcliffe coefficient (NSE) = 0.73, percent bias (PBIAS) = 3.9%, ratio of the root mean square error to the standard deviation of measured data (RSR) = 0.52] and validated for the period 1999-2002 (NSE=0.66, PBIAS = 8.7%, RSR = 0.59) for the Gin catchment. The temporal transferability of the calibrated model parameters was tested using two scenarios which formulated based on the temporal lag between the calibration period and the transfer period: scenario A having a 4-year time lag and scenario B having a 8-year time lag. Scenario A which evaluated the model performance using 2003-2006 streamflow data indicated only a marginal loss in the model performance in comparison to the calibration. It showed an overall 'good' performance (NSE=0.64, PBIAS = 8.6%, RSR = 0.59) including promising capability to reproduce the peak flows (<10 th percentile) with Pearson's correlation coefficient of 0.6. However, scenario B which evaluated the model performance using 2007-2010 streamflow data indicated 'unsatisfactory' model performance (NSE=0.42, PBIAS = 13.6%, RSR = 0.76). Therefore, this study suggests that the calibrated parameters of MIKE 11 NAM model can be temporally transferred within a catchment with a 4-year time lag from the calibration period implying the applicability of this modelling framework for rainfall-runoff simulations especially in the catchments where streamflow data is sparse.

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“…The rainfall-runoff inundation model (RRI), capable of simulating rainfall-runoff and inundation simultaneously, was employed in this study to simulate the river flow and inundation. The governing equations of the model are derived based on the mass balance and momentum equations elaborated in Sayama et al, 2012. First, the model's ability to simulate major flood events that occurred in the basin was tested based on an eventbased calibration (Jayapadma et al, 2022). Then it was verified further using APHRODITE rainfall data for the historical period 1980-2000.…”

Section: Flood Modelling Using Rrimentioning

confidence: 99%

19th Annual Meeting of the Asia Oceania Geosciences Society

2023

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This study addresses abrupt global warming and a slowdown thereafter that happened in recent decades. It separated the role of anthropogenic CO2 led linear trend to that from natural factors (volcano and the sun). It segregates a period 1976-1996 where two explosive volcanic eruptions occurred in active phases of strong solar cycles and also the period covers two whole solar cycles. That same period coincided with abrupt global warming. This study suggests that domination of a particular type of ENSO, the Central Pacific (CP) type ENSO and related feedback from water vapour played a crucial role. A plausible mechanism was proposed that could be triggered by explosive volcanos via a preferential North Atlantic Oscillation (NAO) phase. It modulates the CP ENSO via extratropical Rossby wave and affects the Aleutian Low. From that angle, it is possible to explain the disruption of ENSO and Indian Summer Monsoon teleconnection during the abrupt warming period and how it recovered subsequently afterward. Interestingly, individual models and also the CMIP5 model ensemble fails to agree with the observation. This study further explores important contributions due to natural drivers those are missed by models.

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The Effect of Incorporation of Embankment Information for Flood Simulation of the Gin River, Sri Lanka

Cited by 6 publications

References 50 publications

Projection of climate change effects on flood inundation in the Gin River basin, Sri Lanka

Projection of climate change effects on flood inundation in the Gin River basin, Sri Lanka

Temporal Transferability of Calibrated Hydrological Model Parameters: A Case Study of Gin Catchment, Sri Lanka

19th Annual Meeting of the Asia Oceania Geosciences Society

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