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Flood Modelling of the Huong River System in Thua Thien Hué, Vietnam

Oude, Reinout de (2006) Flood Modelling of the Huong River System in Thua Thien Hué, Vietnam.

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Abstract:The Thua Thien Hué province is a quite mountainous in the west part and very flat in the east part of the province, which easily leads to flash floods in the rivers. These floods lead to high inundation levels in this area resulting into huge economical losses and sometimes even to the losses of lives. To prevent the future from these huge inundations again solutions have to be taken which gives the Huong River Basin a better ability to cope with these problems. However, before solutions can be taken, a model has to be set up which will be used to calculate the water level along the river and to investigate where solutions has to be taken and where these solutions has to be implemented. The objective of thesis is to make a calibrated model of the Huong River Basin with the use of the HEC-RAS software. The Huong River Basin lies in the middle of Vietnam in the Thua Thien Hué province, which is a very wet climate. The annual rainfall in this region can reach up to 5,000 millimetres in the western mountains and up to 3,000 millimetres in the city of Hué, this city lies in the western part of the study area. The Huong River Basin consists of four rivers, of which the Huong River is the main river. This river originates in the western mountains and flows then to the plain area near Hué and finally ends in the Tam Giang – Cau Hai lagoon. North of the Huong River originates the Bo river which flows also in eastern direction and confluences with the Huong River near the city of Hué. The two other rivers are the Loi Nong River and the Nham Bieu River. Both rivers originate out of the Huong River. When the Huong River system is modelled in the HEC-RAS software two upstream boundaries are implemented and three downstream boundaries. The two upstream boundaries, one of the Huong River and one of the Bo River, exist out of a flood wave which will run through the model. The three downstream boundaries are needed to give a value for the amount of water which flows out of the river into the lagoon. However, because of the lack a data as downstream boundaries the water levels of the three water stations in the lagoon are used instead of the water level et the end of the river. To calibrate the model the measured water level at Kim Long water station during the floods of November 1999 and November 2004 are compared with the water level calculated by HEC-RAS. To calibrate the model the Manning coefficients are adjusted to get a better fit with the measured water level. After the final en best calibration the goodness-of-fit for both the November 1999 and November 2004 flood are calculated. The November 1999 flood has a goodness-of-fit of 0.253 and the November 2004 flood has a goodness-of-fit of 0.322. This makes that the November 1999 flood has a better fit. Nevertheless gives also the November 2004 flood a indication that the model is well calibrated and useful to determine where problems arise during the November 1999 flood which will now be used as a design flood to calculate the measurements. But, there are still some problems in the model which can partial be solved by implementing better cross sections in the model. Also will downstream data of the rivers itself instead of the lagoon a better indication of the inundation problems in the area near the lagoon. But as is mentioned before, this model can now be a useful model to determine the problems in the Huong River Basin.
Item Type:Essay (Bachelor)
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering BSc (56952)
Link to this item:http://purl.utwente.nl/essays/74801
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