Climate change likely to amplify the floods in HKH region
Published on by Muhammad Shahid Iqbal, Researcher Water Modeling at International Water Management Institute in Academic
Historically several floods occurred in the HKH region, including the most devastating flood of 2010, which killed about 1900 people. According to the available data, losses worth of about 10 billion USD have occurred since 1965 due to floods in the Kabul basin (Baig 2008, Tariq &van de Giesen 2012). This study, therefore, using the SWAT hydrological model and FFA simulated the Kabul river discharge for the past and future time periods (near (2031-2050) and far future (2081-2100)) using two different scenarios: RCP 4.5 and RCP 8.5. FFA has been carried out using historic (1981-2015), near and far future annual peak flows. Main conclusions and recommendations of the current study areas following:
- Mean monthly temperature is expected to rise in the Kabul basin during the near (2031-2050) and far future (2081-2100) periods based on both RCP4.5 and 8.5 scenarios and three GCMs (MIROC5, EC-EARTH, IPSL-CM5A), whereas show a decline based on INM-CM4 GCM for the both periods and RCPs.
- Mean monthly precipitation is also likely to increase in the Kabul basin for both near (2031-2050) and far future (2081-2100) based on EC-EARTH and MIROC5 GCMs for both RCPs, whereas a decrease is expected in the near and far future precipitation based on INM-CM4 GCM for both RCPs, and a mixed response is expected based on IPSL-CM5A.
- Mean monthly river flows are expected to rise in the near (2031-2050) and far (2081-2100) future periods compared to the historic reference period (1981-2000) for on both RCPs and all selected GCMs, except INM-CM4. Increased (decreased) river flows caused by a combined precipitation and temperature (hence snow- and glacier-melt contributions) effect .
- Flood Frequency Analysis (FFA) shows strong increases in the intensity of future peak flows and a reduction in the recurrence period for both the near and far future periods under both RCPs and all GCMs, except INM-CM4. Present day 1 in 50 year floods may occur every 9-10 years. MIROC5 provides an extreme scenario where present day 1 in 50 year peak flow events are expected to occur every 2-3 year.
- The current study results can be used for flood inundation plans, risk assessment and design reviews of the current and future interventions.
The Kabul basin is part of the Indus river system, which is opined to be the hotspot for climate change impacts in future. The Kabul basin is densely populated with a higher flood risk in lower parts of the basin. Results and analyses presented in the current study are vital to understand climate change impacts on river flow variation and extreme events in the HKH region. Kabul basin suffers from annual floods and in particular the 2010 flood had devastating impacts. This first flood frequency study in this basin shows that floods likely increase in severity. The peak flow for 2010 is expected to occur every 2nd – 24th year in the near and far future for RCP 4.5 and 8.5 and three out of four models. Climate change adaptation measures should be incorporated in water plans for this basin to prevent such extreme floods. The current study also suggest to carryout similar analysis in other sub-basins of the HKH-region to mitigate floods risks and to minimize loss to human lives and property.