Abstract
In recent years, losses and damages from flash floods have been steadily increasing worldwide as well as in Vietnam, due to physical factors, human activities, especially under a changing climate. This is a hotspot issue which requires immediate response from scientists and policy-makers to monitor and mitigate the negative impacts of flash floods. This study presents a way to reduce losses through increasing the accuracy of real-time flash flood warning systems in Vietnam, a case study developed for Ha Giang province where the topography is relatively complex with severe flash floods observed. The objective of this paper is to generate the real-time flash flood system based on bankfull discharge threshold. To do this, HEC-HMS model is applied to calibrate and validate observer inflow to the reservoir with nine automatic rain gauges installed. More importantly, on the basic of measured discharge at 35 locations from the fieldtrips, an empirical equation constructed is to identify the bankful discharge values. It bases on the relationship between basin characteristics of river length, basin area and bankfull discharge. The results indicate an effective approach to determine bankfull threshold with the established-empirical equation. On the scale of a small basin, it depicts the consistency of flood status and warning time with the reality. Doi: 10.28991/cej-2021-03091687 Full Text: PDF
Highlights
In recent years, flash flood events have caused serious consequences in Ha Giang, a province in the northwest of Vietnam
The asset and human losses derived from the flash floods are severely recorded in Ha Giang province where its topography is fairly complex with steep slopes
The study is applied to the Nam Ly and Na Nhung basins in Ha Giang province, Vietnam
Summary
Flash flood events have caused serious consequences in Ha Giang, a province in the northwest of Vietnam. It has become more complex and more extreme in frequency of occurrence and intensity. Flash floods have different features from floods in river, notably short time lag and occur in small mountain catchments with few hundred square kilometers or less [3]. This shows that forecasting of flash floods is quite challenging compared to traditional flood forecasting approaches. There are only 33 hourly rainfall stations on 7945.8 square kilometers of the province (http://kttvqg.gov.vn/)
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