Monin Nong

Rapid peri-urban expansion has intensified flood risk in Southeast Asian cities through wetland loss, rural–urban migration, and delayed infrastructure development. This study examines the spatial and temporal dimensions of flood risk in Phnom Penh, Cambodia using a multi-factor framework based on hazard, exposure, vulnerability, and coping capacity. Vulnerability and coping capacity are analysed at both community and household levels. Migrant settlement duration captures differences in exposure and adaptive capacity over time. A composite flood risk index is constructed from survey data using the Rank Order Centroid weighting method. Results show that exposure is the dominant driver of flood risk, exceeding the influence of hazard intensity and largely shaping spatial patterns. Community-level vulnerability and coping capacity exert stronger effects than household-level characteristics, highlighting the importance of infrastructure and local settings. Flood risk varies across migrant groups: new migrants face the highest risk due to elevated exposure and vulnerability, while long-term migrants experience lower risk as adaptive capacity improves over time. However, risk reduction varies across groups, with persistent challenges linked to infrastructure and disaster preparedness systems. These findings highlight the importance of community-scale resilience strategies and targeted infrastructure investment to reduce flood risk in rapidly urbanising cities.

Urban flooding increasingly challenges rapidly expanding cities in developing countries. Migration, weak urban planning, and unregulated land use collectively intensify flood risk. Effective flood mitigation requires understanding the dynamic interactions between physical and social processes that shape urban vulnerability. This study examines how migrant households in flood-prone areas adapt over time to enhance resilience. The study applies a dynamic flood risk framework using settlement-duration cohorts from 560 peri-urban households in Phnom Penh. Findings show that rapid in-migration into flood-prone zones has increased physical exposure to flood hazards. Migrants’ adaptation and resilience, however, develop gradually, reducing vulnerability only over time. Newer migrants remain highly vulnerable due to insecure housing, limited renovation, and restricted access to flood information. Long-term migrants face structural and economic challenges, including low income, limited access to credit, and deteriorating housing conditions. Mid-term migrants demonstrate the strongest adaptive capacity, supported by stable income, housing investment, and access to flood information. Overall, the study contributes to more dynamic urban risk frameworks that incorporate demographic and socioeconomic transitions. These insights are relevant for other rapidly growing cities, particularly those in Southeast Asia.

Flooding poses a major hazard to rapidly urbanising cities in Southeast Asia, and risks are projected to intensify under climate change. Accurate risk assessment, however, is hindered by scarcity of hydrological and topographic data. Focusing on the Lower Prek Thnot River Basin, a peri-urban catchment of Phnom Penh, Cambodia, the study applied the Rainfall–Runoff–Inundation model and systematically augmented inputs: hourly satellite rainfall data, field-surveyed river cross-sections and representation of hydraulic infrastructure such as weirs and pumping. Validation used Sentinel-1 SAR-derived flood-extent maps for the October 2020 event. Scenario comparison shows that rainfall input and channel geometry act synergistically: omitting either degrades performance and spatial realism. The best configuration (Sim. 5) Accuracy = 0.891, Hit Ratio = 0.546 and True Ratio = 0.701 against Sentinel-1, and reproduced inundation upstream of weirs while reducing overestimation in urban districts through pumping emulation. At the study’s 500 m grid, updating land use from 2002 to 2020 had only a minor effect relative to rainfall, geometry and infrastructure. The results demonstrate that targeted data augmentation—combining satellite products, field surveys and operational infrastructure—can deliver robust inundation maps under data scarcity, supporting hazard mapping and resilience-oriented flood management in rapidly urbanising basins.

Migration forces rural people to find more and better jobs, which is key in generating incomes to sustain livelihoods and ensure food security in times of environmental change. In addition to agricultural production, climate change affects health, water, and energy resources and causes migration and conflict. The impacts of climate change on men and women can also differ in terms of employment, natural resource management, social norms, gender stereotypes, socio[1]economic opportunities, and adaptation to new technologies. Greenhouse gas emissions from production, transportation, and energy consumption will increase in urban areas due to various developments such as infrastructure. At the same time, agricultural land and corresponding activities in rural areas may be at risk of abandonment due to migration to cities or neighbouring countries. Moreover, falling into debt is one of the main reasons why remote villagers, both men and women, migrate to find work in the cities. The reasons behind these debts can be related to crop damage caused by natural disasters or other associated events. The migration burdens elderly mothers or grandmothers who take care of the children and grandchildren left behind, in addition to the uptake of many other household responsibilities. Using a mixed-method approach, this study examined the association between climate change and migration in the three Cambodian communes of Kratie, Mondulkiri, and Steung Treng Provinces. Data was collected from 240 households with migrant members. The study aimed: (1) To understand trends of past and present weather and migrations patterns in rural communities of Cambodia, and (2) to analyse how climate change impacts migration patterns and suggest sustainable coping strategies appropriate for rural settings. This study suggests that climate change and migration are linked. Temperatures have increased, and the rainy and dry seasons have become irregular. The income loss from damaged crops caused by extreme weather events is one of the causes of migration. Usually, villagers migrate short-term to ensure their family has enough money to survive; after earning enough money, they return to their farming activities. Most migrants are of working age and migrate to the capital city of their province or other provinces to work in garment factories, construction sites, or labouring work. Political factors do not seem significant in influencing migration and its patterns. Furthermore, climate hazards, such as droughts, high temperatures, floods, and windstorms, were also not perceived as direct causes of migration. Some villagers faced family burdens, dependency, and health issues yet believed those factors were unlikely to contribute to the migration. This study finds that social and economic drivers were the key factors pushing people to migrate. These include poverty, indebtedness, transfer of workplace to another location, searching for the right jobs, food insecurity, unemployment, lost land or house, and decreased crop yields. The study suggests that climate change-induced extreme events are the root causes of losses and damages, destroying properties or assets, crops, livestock, and poultries, leading to income loss and poverty. Poverty and indebtedness firmly push family members to migrate for better employment opportunities. To improve local livelihoods and reduce migration, the following recommendations are suggested: (1) Provide training on agricultural practices that are resilient to climate change. (2) Provide irrigation systems and training on practical water usage to improve agricultural production and yields, diversify agrarian activities, and increase local farming jobs. (3) Enhance local participation and active engagement in community development planning and decision-making processes toward improving climate resiliency.

Water is central for a variety of livelihoods, development, economic growth, and food production. It is also very important in the large deltas of South and Southeast Asia. Yet, water is turning into a scare resource and global climate change is making its availability more unpredictable. Commercial interests and infrastructure development are also competing for water resources, sometimes at the expense of local smallholders. This report, which is a desk study combined with stakeholder interviews, aims to map out the issues and the previously unknown challenges to efficient water and land management for poverty alleviation and food security. It also serves as a basis for an empirical case study on the same topic. The report illuminates the political economy of land-water resources in the floodplains around the Tonle Sap Lake which constitutes the upper part of the Mekong River Delta and shares seasonal fluctuations and livelihood patterns. The report identifies key challenges for land-water integrity and multi-functionality in food security, nutrition and income impacts for different local producers. The versatile delta landscape and its livelihoods are a complex ecosystem; the driving factors include seasonal water flow variations, the construction of upper Mekong dams, climate change, and the minimal regulations of local resource governance. This evidently makes the governance challenge both immense and urgent. This report maps out opportunities from national to local levels for promoting more systematic, productive and inclusive land-water management. The roles of formal and informal actors within political spaces, their influence on policy and practice, and opportunities to influence these actors are of particular interest. In pursuing the above, the report applies a political economy approach, where the role of the state, its policies and resource allocation are in focus. This also includes the presence of politically and commercially vested interests and how civil society is involved in the general strife for food security and poverty alleviation. The political economy approach constitutes a holistic analysis of how a society is governed and who possesses and utilises which power in order to pursue their interests. At the core of the political economy approach is therefore the illumination of power (and powerlessness) through analysis of actors or a group of actors and their particular interests. The empirical realms in this report focus on contemporary resource management, its institutions and actors. The conclusions are as follows: The conclusions are as follows:The policies and legal frameworks are tentatively progressive, but still sectoral and sometimes fragmented. Institutional structures and agency interests in horizontal coordination and vertical implementation are considerably weaker than the laws and policies themselves. While concerned ministries have achieved a lot, they have not managed to effectively collaborate and work across sectors and ministries. They continue to treat landscapes in a segmented manner. Many policies fall short because there are a lack of adequate resources and local incentives to implement and follow-up on the ground. To systematically monitor the implementation of policies, studying their true weaknesses, feeding back to the concerned ministries and amending the policies according to their existing weaknesses, would further the efficacy of the system. The decentralisation reform programme at the sub-national level is one of the most promising governance reforms in post-war Cambodia. However, in its current version, it is not sufficient, because the scale of the problems at stake are typically greater than the commune jurisdiction. To complete the halfway reform of a “unified administration” at the district level, integrating agriculture, environment and water mandates may be the most important reform for the long-term future. This is a hypothetical scenario since the commune councils may not be as accountable to their local constituency as they were pre-2017. Overall, increased agricultural output, green revolution, mechanisation, and efficien market access are favoured in many policies and plans. Yet, fisheries, especially small- scale ones, are partially neglected in spite of the huge value, poverty alleviation abilities, and nutritional quality. The policy recommendations include: The national government system would benefit from an establishment of mandatory cross-ministerial meetings on a regular basis, facilitated by existing/new coordination structures leading to monitorable cross-sector and cross-agency actions towards more integrated water and land management. A systematic empirical monitoring of the rollout of policies would be very valuable since our analysis revealed that the weakest links in the policy work are the implementation, the upholding of the quality of interventions, and the safeguarding of the sustainability of already established policies. To further support the IWRM implementation, a planning process based on hydrological units (basins and sub-basins), resource inventories, development priorities for key social indicators (e.g., poverty, nutrition and gender), and arising trade-offs needs to be established. The recent decision to integrate water, agriculture and environment at the district level needs to be given full support, bringing in fisheries to the mandate. The rules for il/legal fisheries need to be clarified and the absence of efficient monitoring of fishing practices needs to be addressed. The government has recently promoted a partnership between public, private and farmer agents to enhance agricultural production and productivity for better food security. To push this further is a worthwhile opportunity.