Samenvatting

Floods are the most damaging natural hazard in the world. Better understanding on the flood hazard phenomenon and its potential consequences in our society is crucial for the development of flood control policies, risk reduction projects and other types of flood management strategies. Ho Chi Minh city plays a major role as the financial hub of Vietnam. In recent years, Urban flooding has become a wide-spread phenomenon and a major concern in Ho Chi Minh City that has been accompanying the city’s rapid growth. In recent decades the amount of flooded locations, flood frequencies and flood duration has steadily increased and has caused substantial economic and social losses.
Given its distinct topographical location in the low- lying delta area as well as the projected changes in climate and urban expansion, flood risk is expected to further increase, putting a major pressure on the city’s development.
In this research, the focus was in District 6, the optimal study area for the project, determined via a multi -criteria analysis. District 6 is usually affected by flooding and often left behind when it comes to public interest. Flooding in this area is mostly caused by rainfall but also high tides by the Saigon river. The vulnerability in this area is high, originated by a combination of factors such as low ground level, significant land-subsidence and the water line, which surrounds most of the area.
The methodology of this research was structured according to the flood risk methodology framework (Pistrika & Tsakiris, 2007) and involved the quantification of the hazard via 2D flood modelling software, and the estimation of its vulnerability by calculating the direct economic flood loss via stage-damage curves.
On the basis of the results of this study, is concluded that the flood risk for District 6 in Ho Chi Minh City increases exponentially when both scenarios are compared, 2025 and 2050 respectively. In 2025, however, flood depth and area varies more between the three different return periods due to the fact that in 2050 most of the area is already severely flooded in the smaller return period. Simulations including variation in precipitation have shown that a 20%
reduction in damage occurs when a decrease of 30% in precipitation takes place.
The effects of the drainage in District 6, which is known to be insufficient and often obstructed, were neglected during the hazard analysis, making the results presented by this research more conservative and safer. When it comes to the flood risk, the results of the EAD for District 6 points to a damage per year of USD 0,48 million by 2025 reaching USD 0,78 by 2050. These values reflect the latest and worst case scenarios, which includes increase in storminess and land subsidence. Land subsidence, specifically, contributes to a severe increase on the study area’s flood hazard and consequently flood risk. The simplified and yet inclusive approach implemented in this research reveals suitable for assessing flood risk in urban areas, where complex background exists, under a strict time-frame and data scarcity.