TY - JOUR

T1 - Effective Adaptation Options to Alleviate Nuisance Flooding in Coastal Megacities

T2 - Learning From Ho Chi Minh City, Vietnam

AU - Scheiber, Leon

AU - Sairam, Nivedita

AU - Hoballah Jalloul, Mazen

AU - Rafiezadeh Shahi, Kasra

AU - Jordan, Christian

AU - Visscher, Jan

AU - Zadeh, Tara Evaz

AU - Oostwegel, Laurens J.N.

AU - Schorlemmer, Danijel

AU - Son, Ngo Thanh

AU - Nguyen Quan, Hong

AU - Schlurmann, Torsten

AU - Garschagen, Matthias

AU - Kreibich, Heidi

N1 - Publisher Copyright: © 2024. The Author(s).

PY - 2024/11/18

Y1 - 2024/11/18

N2 - The economies and livelihoods of many coastal megacities are at serious risk from flooding, despite investments in flood defenses. For instance, in Ho Chi Minh City, the construction of a large-scale ring-dike has mitigated negative effects from storm surges, yet damage is still frequently caused by high-intensity rainfalls leading to nuisance flooding, which is responsible for the highest proportion of flood losses in the city today. Because sustainable flood risk management requires detailed spatial information, we analyze the local risk and its components based on a chain of novel models previously calibrated and validated for Ho Chi Minh City. Furthermore, we assess the effectiveness of two decentralized adaptation options, namely private precautionary measures and rainwater retention, for mitigating pluvial flooding. Our integrated risk assessment reveals that the approaches are complementary, which is a major advantage for their implementation. Implementation of both approaches has the potential to reduce the expected annual damage and the number of annually affected households by 16% and 56%, respectively. This is also reflected in a significant reduction of annual losses per household, which we propose as an additional, people-centered indicator of flood risk. Moreover, these measures are well-suited to strengthen citizen participation in risk reduction beyond top-down protection schemes. Complementing the ring-dike with decentralized adaptation options can therefore be seen as an effective and generic strategy to alleviate the impacts of nuisance flooding in coastal megacities, such as Ho Chi Minh City, and should be incentivized by decision-makers. Aside from hydrological and metocean site conditions, both the methodology and findings of this study are transferrable to any coastal megacity facing similar challenges.

AB - The economies and livelihoods of many coastal megacities are at serious risk from flooding, despite investments in flood defenses. For instance, in Ho Chi Minh City, the construction of a large-scale ring-dike has mitigated negative effects from storm surges, yet damage is still frequently caused by high-intensity rainfalls leading to nuisance flooding, which is responsible for the highest proportion of flood losses in the city today. Because sustainable flood risk management requires detailed spatial information, we analyze the local risk and its components based on a chain of novel models previously calibrated and validated for Ho Chi Minh City. Furthermore, we assess the effectiveness of two decentralized adaptation options, namely private precautionary measures and rainwater retention, for mitigating pluvial flooding. Our integrated risk assessment reveals that the approaches are complementary, which is a major advantage for their implementation. Implementation of both approaches has the potential to reduce the expected annual damage and the number of annually affected households by 16% and 56%, respectively. This is also reflected in a significant reduction of annual losses per household, which we propose as an additional, people-centered indicator of flood risk. Moreover, these measures are well-suited to strengthen citizen participation in risk reduction beyond top-down protection schemes. Complementing the ring-dike with decentralized adaptation options can therefore be seen as an effective and generic strategy to alleviate the impacts of nuisance flooding in coastal megacities, such as Ho Chi Minh City, and should be incentivized by decision-makers. Aside from hydrological and metocean site conditions, both the methodology and findings of this study are transferrable to any coastal megacity facing similar challenges.

KW - climate change adaptation

KW - coastal megacities

KW - HCMC

KW - integrated risk assessment

KW - urban flooding

KW - urbanization

UR - http://www.scopus.com/inward/record.url?scp=85209931053&partnerID=8YFLogxK

U2 - 10.1029/2024EF004766

DO - 10.1029/2024EF004766

M3 - Article

AN - SCOPUS:85209931053

VL - 12

JO - Earth's future

JF - Earth's future

SN - 2328-4277

IS - 11

M1 - e2024EF004766

ER -