Dams and Floods

The possible mitigation of floods by dams and the risk to dams from floods are key problems. The People's Republic of China is now leading world dam construction with great success and efficiency. This paper is devoted to relevant experiences from other countries, with a particular focus on lessons from accidents over the past two centuries and on new solutions. Accidents from floods are analyzed according to the dam's height, storage, dam material, and spillway data. Most of the huge accidents that have been reported occurred for embankments storing over 10 hm3. New solutions appear promising for both dam safety and flood mitigation.

From risk control to resilience: developments and trends of urban roads designed as surface flood passages to cope with extreme storms

Urban roads can be designated as surface flood passages to transport excess runoff during extreme storms, thereby preventing local flooding, which is known as the major drainage system. However, this practice poses significant risks, including human loss and property damage, due to the high flow rate and velocity carried by roads. Moreover, urban roads with low flood-resilience may significantly hamper the transportation function during severe storms, leading to dysfunction of the city. Therefore, there is an urgent need to transform risk-oriented flood passages into resilient urban road-based flood passages. This paper presents a systematic review of existing methodologies in designing a road network-based flood passage system, along with the discussion of new technologies to enhance system resilience. The study also addresses current knowledge gaps and future directions. The results indicate that flood management measures based on the urban road network should integrate accessibility assessment, lifeline and emergency planning to ensure human well-being outcomes. Furthermore, the special needs and features of vulnerable groups must be taken into serious consideration during the planning stage. In addition, a data-driven approach is recommended to facilitate real-time management and evaluate future works.

Long-Term Improvement in Precautions for Flood Risk Mitigation:A Case Study in the Low-Lying Area of Central Vietnam

Local actors appear as inseparable components of the integrated flood risk mitigation strategy in Vietnam.Recognizing this fact,this study examined the long-term improvement in precautions taken by commune authorities and households between two major floods in 1999 and 2017 by applying both quantitative and qualitative methods.Two flood-prone villages were selected for a survey;one in a rural area and the other in a suburban area of Thua Thien Hue Province,central Vietnam.The findings indicate that most villagers doubted the structural works’efficacy and were dissatisfied with the current efforts of local authorities.Households’self-preparation thus became the decisive factor in mitigating risk.While most households have paid greater attention to flood precautions in 2017,others seem to be lagging.Poverty-related barriers were the root causes restraining households in both rural and suburban villages.The suburban riverine residents were further identified as vulnerable by their limitations in upgrading structural measures,which was ascribed to the inconsistency in the ancient town’s preservation policy.This multidimensional comparison,in terms of vulnerability,emphasized the importance of space-function links in the suburb and the contradictions of different policy initiatives,such as landscape rehabilitation,disaster prevention,and livelihood maintenance.

The“Urban Water Machine”:A Landscape-Based Approach for Urban Planning

Climate change is confronting cities across the globe,resulting in extreme weather conditions:floods,droughts,forest fires,and hurricanes.These natural hazards have become so severe that it is increasingly difficult to manage them.Urbanization,which has marginalized nature and water over time,has exacerbated these conditions.By replacing natural features with hardscape,cities are less adaptive to environmental fluctuations,and climate-related hazards are intensified,through heat island effect for example.Streets,squares,and parts of the city are inundated by water.The need to give space to water and nature in the city is more urgent than ever.The essential relationship between water and humans gave birth to our cities.This relationship has evolved across time and geography,and our current climate and ecological crises are calling us to take the next step in this evolution.Improving natural systems within the city,including a holistic approach for rivers,waterways,and green corridors,will improve resilience to flash floods and drought,contribute to heat mitigation,and improve urban living conditions.It will create possibilities for new economic,environmental,community,and social developments.A contemporary and healthy relationship between humanity and nature requires creating a basic,sustainable,spatial framework that upgrades and connects larger green and water(blue)structures.These blue-green structures should also be linked within the city and within its neighborhoods.The new mechanism to balance water in the city will be an integrated system,what we call the“urban water machine”.By integrating our natural and man-made water systems with each other,and with green spaces in and around the urban environment,we can regenerate the“urban water machine”and use it as the basis for a truly holistic approach to spatial planning.To shape our contemporary relationship with water,it is important to develop both innovative design tools and spatial typologies.A design approach based on the“urban water machine”provides climate adaptive solutions with nature-based design tools within the green landscape framework combined with blue-green design tools in public spaces.Such a holistic approach will help to care for the city as a whole,making them more beautiful,vibrant,and resilient.

Science to support conservation action in a large river system:The Willamette River,Oregon,USA

Management and conservation efforts that support the recovery and protection of large rivers are daunting,reflecting the complexity of the challenge and extent of effort(in terms of policy,economic investment,and spatial extent)needed to afford measurable change.These large systems have generally experienced intensive development and regulation,compromising their capacity to respond to disturbances such as climate change orwildfire.Functionally,large river and basin management require insights gained from social,ecological,geophysical,and hydrological sciences.This multidisciplinary perspective can unveil the integrated relationship between a river network's biotic community and seasonally variableenvironmental conditions that are ofteninfluencedbyhumanactivities.Large rivers andtheir basins are constantly changing due to anthropogenic influences and as climate modifies patterns of temperature and precipitation.Because of these factors,the state of knowledge must advance to address changing conditions.The Willamette River,in western Oregon,USA,is a prime example of a basin that has experienced significant degradation and investment in rehabilitation in recent decades.Innovative science has facilitated development of fine-scale,spatially extensive datasets and models that can generate targeted conservation and rehabilitation actions that are prioritized across the entire river network.This prioritization allows investment decisions to be driven by site-specific conditions while simultaneously considering potentials for ecological improvement.Here,we review hydrologic,geomorphic,ecologic,and social conditions in the Willamette River basin through time—including pre-settlement,river development,andcontemporary periods—andoffer a futurevisionfor consideration.Currently,detailed informationaboutfish populations and habitat,hydrologic conditions,geomorphology,water quality,and land use can be leveraged to make informed decisions about protection,rehabilitation,and development.The time is ripe for strategic management and goal development for the entireWillamette River,and these efforts can be informed by comprehensive science realized through established institutions(e.g.,public agencies,non-profitwatershed groups,Tribes,and universities)focusedon conservation and management.The approaches to science and social-network creation that were pioneered in the Willamette River basin offer insights into thedevelopment of comprehensive conservation-based planning that could be implemented in other large river systems globally.