Analysing the causes of prolonged flooding in the Nhat Le river basin due to the historical flood in 2020

Abstract

     The Nhat Le river system consists of three main rivers, namely Kien Giang, Long Dai and Nhat Le; in which the Kien Giang river flows through Le Thuy and Quang Ninh districts - a lowland area known as the granary but also the "flood-prone area" of Quang Binh province. In-situ data at the Le Thuy hydrological station during 1976-2022 reveals that the water exceeded the Alarm Level 3 in 16 years, including three consecutive years. This study focuses on analysing the causes of prolonged flooding in the Nhat Le river basin and identify out four main groups of reasons: i) the low-lying and concave basin; ii) the deposition of Nhat Le estuary - the unique drainage outlet of the basin; iii) construction of structures and infrastructures on the river and within the basin; and iv) abnormally heavy rainfall coincides with the occurrence of high tide. The analysis and assessment of the above causes will significantly support scientists and management units in having a basis to propose solutions to enhance flood drainage capacity for the study area