A first calibration of the one-dimensional model of the Nhat Le River basin

Abstract

This thesis provides a first draft of a one-dimensional model of the Nhat Le River Basin. The model is almost ready for use due to the short period of time. The model requires at least an adequate calibration before using. With this thesis a first start has been made. Eventually, with the model, the probability of water levels in the Nhat Le River (Quang Binh Province, Vietnam) can be estimated, which are needed for calculation of the embankments height along the Nhat Le River. In the beginning of the project this thesis had another research question. But at the start of the assignment the provided documents did not suffice due to missing and/or wrong drawings, wrong calculations and lack on key input. Some information should be bought and the newly presented documents never came or came too late. Although it didn’t work out as planned, a lot about the Vietnamese culture and organizational structure has been learned. The new research question was originated around the calculations of the newly proposed embankments along the Nhat Le River. The provided documents calculated the levels of the embankments with the old regulations. These calculations were based on the old Vietnamese regulations, which are not sufficient anymore. The new regulations require a one-dimensional model to estimate the highest water level in the river with different frequency floods. Due to the short period of time, the model is not yet ready for implementation. However some recommendations for optimization and further use of the model are given. The one-dimensional model is made with the computer software HEC-RAS. The Water Resources University Hanoi provided the required data, including boundary conditions and cross-sections. Data in Vietnam is not easy to obtain. It took a long time to get the proper information and support from different parties. Although, this assignment is a good first start of modelling the one-dimensional model. In order to establish the final one-dimensional model the following steps should be conducted: - More cross-sections along the Dia Giang and Kien Giang river branches in order to determine the correct slopes of the river branches; - Development of the Dia Giang and Kien Giang river branches with wider cross-sections, including floodplains and storage areas; - Calibration of the Dia Giang river branch; - Calibration of the whole Nhat Le river Branch; - Implementation of the My Trung sluice in the Kien Giang river branch; - Data of different frequency floods in the Dia Giang and Kien Giang river branch to estimate the different high water levels in the main of Nhat Le river in different scenarios; - Clearness about the positions of the newly constructed embankments.