Shallow Geologic Storage of Carbon to Remove Atmospheric CO2 and Reduce Flood Risk.

Geologic carbon storage currently implies that CO2 is injected into reservoirs more than 1 km deep, but this concept of geologic storage can be expanded to include the injection of solid, carbon-bearing particles into geologic formations that are one to two orders of magnitude shallower than conventional storage reservoirs. Wood is half carbon, available in large quantities at a modest cost, and can be milled into particles and injected as a slurry. We demonstrate the feasibility of shallow geologic storage of carbon by a field experiment, and the injection process also raises the ground surface. The resulting CO2 storage and ground uplift rates upscale to a technique that could contribute to the mitigation of climate change by storing carbon as well as helping to adapt to flooding risks by elevating the ground surface above flood levels. A life-cycle assessment indicates that CO2 emissions caused by shallow geologic storage of carbon are a small fraction of the injected carbon.

Secondary benefits of urban flood protection.

The combined effects of urbanization and climate change put a large portion of the population at risk from pluvial, fluvial, and coastal flooding. To continue to strive for sustainable development, cities will need to protect flood-prone areas, but this will require significant investments in both green and grey infrastructure solutions. Yet, a significant financing gap will need to be bridged to increase cities' resilience. The decision as to which flood protection intervention to finance typically includes an analysis of primary costs (construction) and benefits (averted damages). However, an array of potential secondary benefits occur with increased flood protection that are often not assessed, such as increased well-being and ecosystem health. This review provides a timely overview of the secondary benefits of urban flood protection, a brief analysis of whether they have been included in cost-benefit analyses for investments in urban flood protection projects, and a discussion of methodological concerns. Of the twenty projects reviewed, fourteen make mention of secondary benefits, yet only four quantify them in their analysis. Advances in evaluation methodologies may reduce quantification challenges, but a move away from traditional cost-benefit analysis may be necessary to incorporate a full range of secondary benefits. Ultimately, we argue that a more thorough understanding of the secondary benefits of urban flood protection and their quantification methods could unlock additional financing for flood protection infrastructure, especially in urban centers of developing countries.

How path dependency manifests in flood risk management: observations from four decades in the Ennstal and Aist catchments in Austria.

Path dependency occurs when a contingent event predetermines what further steps can be taken and self-reinforcing mechanisms lock-in any further development on a sub-optimal trajectory. Path dependency is a prominent concept in the adaptation pathways literature, but insufficiently defined and operationalised. The present paper empirically tracks all constitutive elements of path dependency for four decades of flood risk management (FRM) in two alpine mountain regions in Austria, the Ennstal and Aist river catchments, using a mixed-methods approach. FRM governance has a critical role whether decisions lead to path dependency. Lock-in manifests not just in technical structures, but also in inertia of incumbent actor coalitions and management paradigms. Sub-optimality is hard to assess for lack of clearly defined protection targets; however, it appears in the ways that structural measures are implemented-too little, too late or with negative impacts on nature conservation. Past floods do not qualify as contingent events, as they have not fundamentally changed FRM practice. By contrast, technological and institutional shifts over longer periods, such as digital hazard maps and EU directives, have gradually reoriented FRM strategies. Institution-based self-reinforcing mechanisms are more prevalent than technology-based self-reinforcing mechanisms. Established actor coalitions combined with institutional density illustrate how those in charge uphold a path to defend their position, power and resources. Our recommendations for how to overcome path dependency in FRM governance are: encourage niche experiments, link FRM more closely with climate change adaptation, revise the national policy framework towards polycentric governance approaches and improve professional training.

The importance of marshes providing soil stabilization to resist fast-flow erosion in case of a dike breach.

Salt marshes provide valuable ecosystem services including coastal protection by reducing wave loading on dikes and seawalls. If the topsoil is erosion resistant to fast-flowing water, it may also reduce breach depth if a dike fails. In this experiment, we quantified the topsoil erosion resistance from marshes and bare tidal flats with different soil types to understand the extent to which they can help reduce breach depth. Intact soil samples were collected from 11 locations in the Netherlands at different tidal elevations and then exposed for 3 h to 2.3 m/s currents. To the samples that remained stable after flow exposure, an artificial crack was made to test their stability following soil disturbance. All samples from the tidal flats were completely eroded, regardless of sediment type. In contrast, all samples from well-established marsh plateaus were stable as long as no disturbances were made, including those with sandy subsoils. After creating artificial cracks, samples with a thin cohesive top layer on top of sandy subsoil collapsed, while marshes with silty subsoils remained stable. Pioneer marshes on sandy substrate without a cohesive top layer were the only vegetated soils that completely eroded. The lower erosion of marshes with either sandy or silty soils compared to bare tidal flats was best explained by the presence of a top layer with belowground biomass, high organic content, high water content, and low bulk density. When analyzing the erodibility of marshes only, fine root density was the best predictor of erosion resistance. This study demonstrates the importance of preserving, restoring, or creating salt marshes, to obtain a topsoil that is erosion resistant under fast-flowing water, which helps reduce breach dimensions if a dike fails. The probability of topsoil erosion in established marshes with sandy subsoil is higher than in silty marshes. A silty layer of cohesive sediment on top of the sand provides extra erosion resistance as long as it does not break. Pioneer marshes that have not developed a cohesive top layer are erosion sensitive, especially in sandy soils. For future marsh creations, using fine-grained sediments or a mixture of sand with silt or clay is recommended.

How Flood Experience and Risk Perception Influences Protective Actions and Behaviours among Canadian Homeowners.

Canada is a country in the midst of a flood management policy transition that is shifting part of the flood damage burden from the state to homeowners. This transition-as well as the large financial losses resulting from flooding-have created a window of opportunity for Canada to implement strategies that increase property owners' capacity to avoid and absorb the financial and physical risks associated with flooding. This work presents foundational research into the extent to which Canadians' flood experience, perceptions of flood risks and socio-demographics shape their intentions and adoption of property level flood protection (PLFP). A bilingual, national survey was deployed in Spring 2016 and was completed by 2300 respondents across all 10 Canadian provinces. The survey was developed using assumptions in existing literature on flood risk behaviours and the determinants of flood risk management in similar jurisdictions. The paper argues that property owners are not willing to accept greater responsibility for flood risk as envisioned by recent policy changes. This finding is consistent with other OECD jurisdictions, where flood risk engagement strategies have been developed that could be replicated in Canada to encourage risk-sharing behaviour.

Flood protection and endogenous sorting of households: the role of credit constraints.

Human migration is increasingly seen as a promising climate change adaptation and flood risk reduction strategy. The purpose of this paper is to investigate how spatial differences in flood risk, due to differences in flood protection, reduce the mobility of vulnerable households through a credit constraint mechanism. Using an equilibrium model with two households types and endogenous sorting, we show how spatial differences in flood protection lead to clustering of vulnerable households in a risky region, in a real-world setting of common United States (US) flood zones. We find clustering effects of some size for flood zones with return periods of less than 30 years.

Analyzing Collaborative Governance Through Social Network Analysis: A Case Study of River Management Along the Waal River in The Netherlands.

Until recently, governmental organizations played a dominant and decisive role in natural resource management. However, an increasing number of studies indicate that this dominant role is developing towards a more facilitating role as equal partner to improve efficiency and create a leaner state. This approach is characterized by complex collaborative relationships between various actors and sectors on multiple levels. To understand this complexity in the field of environmental management, we conducted a social network analysis of floodplain management in the Dutch Rhine delta. We charted the current interorganizational relationships between 43 organizations involved in flood protection (blue network) and nature management (green network) and explored the consequences of abolishing the central actor in these networks. The discontinuation of this actor will decrease the connectedness of actors within the blue and green network and may therefore have a large impact on the exchange of ideas and decision-making processes. Furthermore, our research shows the dependence of non-governmental actors on the main governmental organizations. It seems that the Dutch governmental organizations still have a dominant and controlling role in floodplain management. This challenges the alleged shift from a dominant government towards collaborative governance and calls for detailed analysis of actual governance.

Simulation of the reduction of runoff and sediment load resulting from the Gain for Green Program in the Jialingjiang catchment, upper region of the Yangtze River, China.

A distributed catchment hydrologic model (Hydrological Simulation Program--FORTRAN; HSPF) with improved sediment production processes was used to evaluate the effect of restoration of cultivated land to forest on the reduction of runoff and sediment load in the Jialingjiang basin, which forms part of the Yangtze River basin, China. The simulation results showed that restoration to forest reduced sediment production even in the case of minimum restoration at a threshold catchment slope of 25°, as advocated in the "Gain for Green Program " planned by the Chinese government, even though reduction of the peak flow rate in the river channel was small. The increase in forest area resulting from lowering of the threshold catchment slope reduced sediment production further.

Salt marshes to adapt the flood defences along the Dutch Wadden Sea coast.

Concern about the effects of climate change have set in motion a search for flood protection measures to adapt coastlines to the foreseen accelerated sea level rise. In this context, the potential role of salt marshes to adapt the Wadden Sea's flood defences was explored in the Netherlands Wadden Region Delta Programme. This paper provides an overview of the steps taken by the programme in developing a climate change adaptation strategy so that others might learn from its experiences. The second aim is to summarize the knowledge generated by the programme on the potential role of salt marshes as part of a climate change adaption strategy. Explorative modelling results indicate that Wadden Sea salt marshes affect wave heights, even under extreme conditions. Therefore, a salt-marsh zone in front of the Wadden Sea dikes that could keep pace with sea level rise may result in a reduced dike reinforcement task. A salt marsh potential map gives a rough impression of locations that are potentially interesting for salt marsh conservation and development, based on the current situation, on available information about abiotic conditions for salt marsh formation and the habitats present in the coastal zone. Besides elongated stretches were seminatural salt marshes are already present or developing, several stretches along the Dutch Wadden Sea coast have favourable abiotic conditions for salt marsh development. However, the prospects for integrating salt marshes into flood defences depend also on other aspects. Various nature conservation agreements are in effect with their associated obligations. Furthermore, the foreseen value of salt marsh development compared to traditional reinforcements, in terms of both costs and benefits, must be considered.

A dam or a polder? Stakeholders' dispute over the "right" flood-protection measure in the Czech Republic.

This study focuses on the Skalicka Waterwork (SWW), a largely debated and media-covered water-related/flood-protection project in the Czech Republic. Relying primarily on stakeholder interviews, we traced back and reconstructed the project's development, including its key tipping points reflecting the changing societal preferences for particular measures, yet also the involvement of individual actors/stakeholders, and their differing views. The case eventually crystallized into the "dam versus polder" dispute; concerned by the repercussions for the local landscape, a joint initiative of NGOs, local activists, and politicians not only opposed the dam variant proposed by the state river basin administration but also succeeded in pushing through the alternative scheme of side dry polder. While in many ways specific (e.g. not entailing local resistance), the case exemplifies recent shifts (and respective struggles) within flood risk management, including the increasing importance attributed to complex, catchment-wide perspectives, joint local and scientific knowledge, participatory decision-making processes, or implementation of nature-based and hybrid solutions.

Marshes and Mangroves as Nature-Based Coastal Storm Buffers.

Tidal marshes and mangroves are increasingly valued for nature-based mitigation of coastal storm impacts, such as flooding and shoreline erosion hazards, which are growing due to global change. As this review highlights, however, hazard mitigation by tidal wetlands is limited to certain conditions, and not all hazards are equally reduced. Tidal wetlands are effective in attenuating short-period storm-induced waves, but long-period storm surges, which elevate sea levels up to several meters for up to more than a day, are attenuated less effectively, or in some cases not at all, depending on storm conditions, wetland properties, and larger-scale coastal landscape geometry. Wetlands often limit erosion, but storm damage to vegetation (especially mangrove trees) can be substantial, and recovery may take several years. Longer-term wetland persistence can be compromised when combined with other stressors, such as climate change and human disturbances. Due to these uncertainties, nature-based coastal defense projects need to adopt adaptive management strategies.

A comprehensive computer aided approach to design of earthen dams of dry flood-control reservoirs.

A generalized, comprehensive approach to geotechnical design of earthen dams of dry flood-control reservoirs is developed. It consists of three steps:•In Step 1 three-dimensional (3D) model of terrain and dam subsoil is created. The arrangement of geotechnical layers is reconstructed based on results of geotechnical investigation using geostatistical interpolation, namely, kriging.•Step 2 involves 3D finite element (FE) analysis of transient groundwater flow through the subsoil. Anti-filtration barrier extent is determined by appropriate parametric analysis and the condition of critical hydraulic gradients is verified.•Step 3 concerns deformation assessment and stability analysis. Computations are carried out for selected cross-sections of the dam. At this stage transient coupled problem of deformation and groundwater flow is considered. Stability is assessed with the use of shear strength reduction technique. The proposed approach enables verification of all relevant conditions of limit states. Furthermore, it has been developed in such a way as to enable computationally efficient analysis of considered phenomena. The method constitutes a general framework of design procedure. It can be easily adapted to conform any standard requirements, e.g., by taking adequate values of partial safety factors. Moreover, design solutions can be optimized through parametric analyzes.

Taming the torrent: changes in flood protection at the Gürbe River (Switzerland) from the nineteenth century until today.

This paper analyses the flood protection history of the Gürbe River (Switzerland), a 29-km-long tributary of the Aare River. The upper reach of the river has the character of a mountain torrent and an exceptionally difficult flooding situation. For centuries, riparian communities were only able to take small protective measures. In the mid-nineteenth century, the flood protection strategy changed: between 1855 and 1881, the Gürbe River was channelised and stabilised by a torrent control system. Although the situation improved, flood damage could not be prevented as intended. Therefore, dozens of consecutive projects were implemented-without interruption until today. This paper examines why small watercourses are useful case studies, which protection measures were taken at the Gürbe River, how they corresponded to the prevailing flood protection philosophy, whether they were linked to floods and how flood protection influenced land use. The Gürbe regulation, its consecutive projects and the connected drainages had far-reaching effects: They allowed an intensive agricultural use of the valley floor, the construction of roads, a railway, and new settlements. Consequently, the social and economic pressure on the hazard area increased steadily over the decades. It created a vicious circle: the more that protective structures were built, the more important and profitable flood prevention became, and the more structures were raised. A reevaluation finally took place in the late twentieth century, based on increasing environmental awareness, and fostered by a catastrophic flood. However, the implementation of new projects proved to be difficult due to conflicting interests.

Disaster Risk Reduction Funding: Investment Cycle for Flood Protection in Japan.

BACKGROUND: Investment in disaster risk reduction is crucial in order to mitigate disaster damage. However, for many countries, particularly developing ones, financing investment in disaster risk reduction is challenging. This study aims to examine the factors that affect investments in flood protection and the approaches to securing investments by analyzing investment trends in Japan. METHODS: This study examines 150 years of flood protection and investment cycles that helped reduce damages in Japan. The dataset of flood protection budgets, flood damage, and national income since 1878 was created from public statistics. Documents and reports concerned with disaster management, river management, and finance were examined. RESULTS: The study found five investment cycles of flood protection from the late 19th century to the present. The country established financing mechanisms, such as legislation and long-term plans, following major flood disasters. However, external shocks such as war, economic recession, disaster, and tightened national finance had a major impact on these investments. The fluctuations in the budget created an investment cycle. The country had increased its budget to 0.9% of its national income in the 1990s. It often experienced flood damage accounting for over 1% of the national income until 1961, but succeeded in decreasing the damage to less than 1%, and currently it is limited to less than 0.4%. CONCLUSIONS: The financial mechanisms established from the long-term perspective could support an increase in budgets for flood protection, leading to a decrease in damage. However, established financing mechanisms may weaken the financial flexibility of the country.

Climate change impact assessment, flood management, and mitigation strategies in Pakistan for sustainable future.

In recent years, flooding has not only disrupted social growth but has also hampered economic development. In many nations, this global epidemic has affected lives, property, and financial damage. Pakistan has experienced many floods in the past several years. Due to economic, social, and climate change, Pakistan is at risk of flooding. In order to overcome this problem, the institutions of the country have taken various measures. However, these measures are not sufficient enough to ensure the safety of communities and areas that are prone to disasters with a rapid onset. Hence, it is imperative to forecast future flood-related risks and take necessary measures to mitigate the adverse impacts and losses caused by floods. This article is aimed at exploring floods in Pakistan, analyze the adverse effects of floods on humans and the environment, and propose possible sustainable options for the future. The aqueduct flood analyzer software was used to examine the impact of floods on gross domestic product (GDP), urban damage, and people livelihood, with several years of flood protection plans. To adequately assess the future changes, various flood protection levels and three scenarios for each level of protection were employed, which represent the socio-economic and climate change. The findings revealed that if there is no flood protection, a 2-year flood has a 50% probability of flood occurrence in any given area and may cause no significant impact on GDP, population, and urban damage. Similarly, the probability of a flood occurrence in a five-year flood is 20%, which may cause the country's GDP about $20.4 billion, with 8.4 million population at risk and $1.4 billion urban damage. Furthermore, a 10-year flood has a 10% probability of flood occurrence and may affect the national GDP by $28.9 billion, with 11.9 million affected population and $2.4 billion urban damage in Pakistan. The government of Pakistan should devise appropriate climate change policies, improve disaster preparedness, build new dams, and update relevant departments to mitigate the adverse effects of flooding.

Systemic criticality-a new assessment concept improving the evidence basis for CI protection.

With high certainty, extreme weather events will intensify in their impact within the next 10 years due to climate change-induced increases in hazard probability of occurrence and simultaneous increases in socio-economic vulnerability. Data from previous mega-disasters show that losses from disruptions of critical services surpass the value of direct damages in the exposed areas because critical infrastructures [CI] are increasingly (inter-) dependent. Local events may have global impacts. Systemic criticality, which describes the relevance of a critical infrastructure due to its positioning within the system, needs to be addressed to reduce the likelihood of cascading effects. This paper presents novel approaches to operationalise and assess systemic criticality. Firstly, the paper introduces systemic cascade potential as a measurement of systemic criticality. It takes the relevance of a sector and the relevance of its interdependencies into account to generate a relative value of systemic importance for a CI sector. Secondly, an exemplary sectoral assessment of the road network allows reflecting the spatial manifestation of the first level of cascading effects. It analyses the impact of traffic interruptions on the accessibility of critical facilities to point out the systemically most critical segments of the municipal road network. To further operationalise the spatial dimension of criticality, a normative assertion determining the worthiness of protection of system components is required. A nationwide spatial flood protection plan incorporates this aspect in Germany for the first time. Its formal approval process was initiated in February 2020.

Influence of risk factors and past events on flood resilience in coastal megacities: Comparative analysis of NYC and Shanghai.

Coastal flood protection measures have been widely implemented to improve flood resilience. However, protection levels vary among coastal megacities globally. This study compares the distinct flood protection standards for two coastal megacities, New York City and Shanghai, and investigates potential influences such as risk factors and past flood events. Extreme value analysis reveals that, compared to NYC, Shanghai faces a significantly higher flood hazard. Flood inundation analysis indicates that Shanghai has a higher exposure to extreme flooding. Meanwhile, Shanghai's urban development, population, and economy have increased much faster than NYC's over the last three decades. These risk factors provide part of the explanation for the implementation of a relatively high level of protection (e.g. reinforced concrete sea-wall designed for a 200-year flood return level) in Shanghai and low protection (e.g. vertical brick and stone walls and sand dunes) in NYC. However, individual extreme flood events (typhoons in 1962, 1974, and 1981) seem to have had a greater impact on flood protection decision-making in Shanghai, while NYC responded significantly less to past events (with the exception of Hurricane Sandy). Climate change, sea level rise, and ongoing coastal development are rapidly changing the hazard and risk calculus for both cities and both would benefit from a more systematic and dynamic approach to coastal protection.

A framework for performing comparative LCA between repairing flooded houses and construction of dikes in non-stationary climate with changing risk of flooding.

Sustainable flood management is a basic societal need. In this article, life cycle assessment is used to compare two ways to maintain the state of a coastal urban area in a changing climate with increasing flood risk. On one side, the construction of a dike, a hard and proactive scenario, is modelled using a bottom up approach. On the other, the systematic repair of houses flooded by sea surges, a post-disaster measure, is assessed using a Monte Carlo simulation allowing for aleatory uncertainties in predicting future sea level rise and occurrences of extreme events. Two metrics are identified, normalized mean impacts and probability of dike being most efficient. The methodology is applied to three case studies in Denmark representing three contrasting areas, Copenhagen, Frederiksværk, and Esbjerg. For all case studies the distribution of the calculated impact of repairing houses is highly right skewed, which in some cases has implications for the comparative LCA. The results show that, in Copenhagen, the scenario of the dike is overwhelmingly favorable for the environment, with a 43 times higher impact for repairing houses and only 0% probability of the repairs being favorable. For Frederiksværk and Esbjerg the corresponding numbers are 5 and 0.9 times and 85% and 32%, respectively. Hence constructing a dike at this point in time is highly recommended in Copenhagen, preferable in Frederiksværk, and probably not recommendable in Esbjerg.

Life cycle assessment of stormwater management in the context of climate change adaptation.

Expected increases in pluvial flooding, due to climatic changes, require large investments in the retrofitting of cities to keep damage at an acceptable level. Many cities have investigated the possibility of implementing stormwater management (SWM) systems which are multi-functional and consist of different elements interacting to achieve desired safety levels. Typically, an economic assessment is carried out in the planning phase, while environmental sustainability is given little or no attention. In this paper, life cycle assessment is used to quantify environmental impacts of climate change adaptation strategies. The approach is tested using a climate change adaptation strategy for a catchment in Copenhagen, Denmark. A stormwater management system, using green infrastructure and local retention measures in combination with planned routing of stormwater on the surfaces to manage runoff, is compared to a traditional, sub-surface approach. Flood safety levels based on the Three Points Approach are defined as the functional unit to ensure comparability between systems. The adaptation plan has significantly lower impacts (3-18 person equivalents/year) than the traditional alternative (14-103 person equivalents/year) in all analysed impact categories. The main impacts are caused by managing rain events with return periods between 0.2 and 10 years. The impacts of handling smaller events with a return period of up to 0.2 years and extreme events with a return period of up to 100 years are lower in both alternatives. The uncertainty analysis shows the advantages of conducting an environmental assessment in the early stages of the planning process, when the design can still be optimised, but it also highlights the importance of detailed and site-specific data.

Current status and restoration options for floodplains along the Danube River.

Floodplains are key ecosystems of riverine landscapes and provide a multitude of ecosystem services. In most of the large river systems worldwide, a tremendous reduction of floodplain area has occurred in the last 100 years and this loss continues due to pressures such as land use change, river regulation, and dam construction. In the Danube River Basin, the extent of floodplains has been reduced by 68% compared to their pre-regulation area, with the highest losses occurring in the Upper Danube and the lowest in the Danube Delta. In this paper, we illustrate the restoration potential of floodplains along the Danube and its major tributaries. Via two case studies in the Upper and Lower Danube, we demonstrate the effects of restoration measures on the river ecosystem, addressing different drivers, pressures, and opportunities in these regions. The potential area for floodplain restoration based on land use and hydromorphological characteristics amounts to 8102 km(2) for the whole Danube River, of which estimated 75% have a high restoration potential. A comparison of floodplain status and options for restoration in the Upper and Lower Danube shows clear differences in drivers and pressures, but certain common options apply in both sections if the local context of stakeholders and societal needs are considered. New approaches to flood protection using natural water retention measures offer increased opportunities for floodplain restoration, but conflicting societal needs and legal frameworks may restrict implementation. Emerging issues such as climate change and invasive non-native species will need careful consideration in future restoration planning to minimize unintended effects and to increase the resilience of floodplains to these and other pressures.