Project Background:Flooding is a common hydrological disaster in Indonesia, especially in high-density urban areas where only have limited open spaces, which also align with rapid urban growth that is not managed and planned properly. Moreover, there have been several flood mitigation programs which are mainly focused on structural conventional measures such as building water embankments. However, the effectiveness of this measure is still questionable since some areas are still often flooded. Realizing this challenge, Nature-based solutions have a crucial role in flood risk reduction through protecting, restoring, and managing modified ecosystems in high density urban areas.

Aims and Objectives:- To enrich research on the application of NBS as a solution for urban flood management.- To explore the challenges and gaps for implementing NBS that will help the decision maker and policy maker in making decisions.

Methodology:- Data analysis : mixed-method (quantitative, qualitative, spatial) approach to explore the challenges and the gaps in implementing NBS.- Data collection : secondary data collection (literature review and online news) and primary data collection (in-depth interview, observation from worldview image and field documentation)

Key finding:- The challenges for implementing NBS in high-density urban settlements are influenced by the adaptability of the scale, budget, and natural characteristics of urban settlement in that area.- Meanwhile, the gaps in implementing NBS based on institutional lens include cost-effectiveness, unclear system in current law to integrate NBS into practice, operational capacity, and political aspects.

Keywords:Nature-based solution, High-density settlement, Disaster risk reduction