Climate change will increase the intensity and frequency of flood and drought events and the global population exposed to these extreme events, thereby enhancing economic damage. Therefore, adaptation measures should be taken to combat the inevitable consequences of climate change, particularly flooding and water scarcity. However, quantitative and concrete views on what adaptation measures should be taken have yet to be explored, especially in developing countries. Hence, in this study, the effect of several combinations of adaptation measures was examined to address both the future extremes in the Chao Phraya River in Thailand. The selected adaptation measures were (i) structural measures, which include dam construction, dam capacity enhancement, use of water-efficient irrigation equipment, and diversion channels, and (ii) non-structural measures, which include reforestation, changing the reservoir operation rules, and retention area enhancement. Future climate scenarios were constructed from the bias-corrected outputs of three general circulation models from 2080 to 2099 under RCP4.5 and RCP8.5.

Future flood and drought risk were analyzed using the number of flooding days and cumulative abstraction to demand (CAD) index, respectively. The major findings that can be drawn from this study are as follows: (i) the structural measures are capable of reducing the number of flooding days and increasing the CAD index; however, this pattern varies from region to region within the basin. (ii) the non-structural measures reduced both flooding days and CAD index, significantly impacting the basin’s water availability during the dry season. The reduction of the CAD index was mainly due to the increased evapotranspiration from the reforested land use that resulted in a decreased runoff. (iii) the adaptation portfolio (combination of structural and non-structural measures) exhibited a reduced number of flooding days and increased CAD index similar to the structural measures. The results revealed that the adaptation measures for flood or drought risk reduction could negatively impact the risk of the other hazard (i.e., reforestation reduces the flood risk but increases the drought risk). Therefore, different combinations of adaptation measures and basin-wide actions would allow us to better address the tradeoffs between these extremes and measures taken at different temporal and spatial scales.

How to cite: Padiyedath Gopalan, S., Hanasaki, N., and Oki, T.: Adaptation portfolio to combat future climate change impacts in the water sector of the Chao Phraya River Basin, Thailand, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13979, https://doi.org/10.5194/egusphere-egu23-13979, 2023.

Complex interactions involving climatic features, socio-economic vulnerability or responses, and long impact transmissions are associated with substantial uncertainty. Physical climate storylines are proposed as approach to explore complex impact transmission pathways and possible alternative unfolding of event cascades under future climate conditions. These storylines are particularly useful for climate risk assessment for complex domains, including event cascades crossing multiple disciplinary or geographical borders. For an effective role in climate risks assessments, practical guidelines are needed to consistently develop and interpret the storyline event analyses.

This presentation elaborates on the suitability of physical climate storyline approaches involving climate event induced shocks propagating into societal impacts. It proposes a set of common elements to construct the event storylines. In addition, criteria for their application for climate risk assessment are given, referring to the need for storylines to be physically plausible, relevant for the specific context, and risk-informative.

A number of examples of varying scope and complexity are presented, all involving the potential climate change impact on European socio-economic sectors induced by remote climate change features occurring far outside the geographical domain of the European mainland. The storyline examples illustrate the application of the proposed storyline components. It thereby contributes to the standardization of the design and application of event-based climate storyline approaches.

How to cite: Van Den Hurk, B. and the RECEIPT project team: Climate impact storylines for assessing socio-economic responses to remote events, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1180, https://doi.org/10.5194/egusphere-egu23-1180, 2023.

Increasingly severe drought events demand a basis for prioritizing water uses and protection goals. In addition to classical methods of hydrological design, model experiments can support such aims. They can help investigate the response of hydrological systems to scenarios of exacerbated drought forcing. For known events of the past they might ask: "how much more would water resources be depleted, if forcing conditions had been more severe?". In such a stress-testing approach, this study investigated the sensitivity of low flows and low spring discharges to a range of exacerbated antecedent forcing conditions for a multi-catchment and multi-spring dataset in southwest Germany. Different model realizations for the forcing groundwater recharge, a baseflow separation and various conceptual groundwater storage and release models were combined into a model ensemble and system responses were analyzed in terms of elasticity metrics. Stress was applied as a systematic reduction in groundwater recharge with different magnitudes over different time periods preceding the main event of drought impact. All scenarios caused further reductions in low flow and spring discharge compared to the reference simulations. The presentation elaborates systematic thresholds: for example, the low-flow response of some catchments becomes maximal after a few months, and in others only after two years of stress duration. The experiments illustrate the sensitivities within the study area and allow to expand the derived 'story' as: "in a hydrological systems with (certain, e.g.) hydrogeological characteristics, low flows as in a (certain) memorable summer might be further depleted up to a (certain) maximum additional amount under (certain) drier preceding conditions". However, the importance of a specifically adapted model architecture as well as the estimation of model-related uncertainties becomes apparent from the ensemble experiment. Applied for selected well-validated model structures, the approach can help elucidate and communicate potential limits of drought stress.

How to cite: Stahl, K., Hellwig, J., and Stoelzle, M.: A model ensemble-elasticity-stress test for drought impact on spring discharge and low flow, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6482, https://doi.org/10.5194/egusphere-egu23-6482, 2023.

Agriculture is one of the most vulnerable sectors to changes in climate patterns. Moreover, climate change is a complex and interdisciplinary problem, where natural processes are closely intertwined with socio-economic aspects, especially in areas where human activities are widespread. Thus, when planning for natural resources management, it becomes essential to consider how storylines, attitudes and behaviours can influence the decision-making towards adaptation measures. In particular, when considering an agricultural system, farmers are key agents that cannot be neglected, as the decision to adapt or to change their agricultural practice is ultimately in the hands of the individuals. Understanding the reasoning behind farmer adaptation can help create a sounder framework to recognize farmers’ awareness and experiences regarding climate change, while reinforcing their resilience to face climate change scenarios. Consequently, finding patterns in attitudes and similarities between farmers is essential both to better share an overall picture of climate change effects and perspectives in a specific study area and to summarize the complex set of factors influencing farmers’ behaviours to facilitate their modelling.

Different tools and methods have been provided by the literature in the last two decades to delve into farmers’ attitudes and perspectives regarding climate change. One of the most used tools are structured surveys, mainly due to their strongly case-specific nature and the capacity to synthesize climate change scenarios in a standardized way. Here, we provide an overview of the results obtained through a survey of 460 farmers from northern Italy about climate change risk awareness, perceived impacts, and adaptive capacity. In addition to a descriptive statistical analysis to delve into farmers’ profiles and farming characteristics, this triple-loop approach was analysed through Multiple Correspondence Analysis (MCA), an interesting data analysis technique that allows to highlight underlying structures in categorical data used to recap farmers’ behaviours and define the association between dependent and independent variables. The resulting factor map allows for the identification of those variables that most explain the variance in the dataset and expected similarities and differences between respondents. The obtained results show how certain variables describing the agricultural practice of the respondents, such as farm extension or the preferred irrigation method, are key driving factors in differentiating and grouping individuals’ behaviour. In general, farmers with the same modus operandi share similar behaviour with respect to other aspects of their activity (e.g., water source). Interestingly, and contradicting similar experiences from the literature, this pattern differs among farmers with comparable demographic background, requiring more attention to farmers’ heuristics. These results can be useful in multiple ways: from creating an informative picture of farmers’ attitudes and concerns regarding climate change in a certain area, to its application in profiling farmers to identify common demands and shared worries; from helping with the creation of customized policies at the regional scale from a bottom-up approach, to the implementation of farmers’ profiles into Agent-Based Models to reinforce the human dimension in decision-making processes.

How to cite: Ferrari, L., Ricart, S., Gandolfi, C., and Castelletti, A.: Underlying farmers' storylines and behaviour on climate change to reinforce risk assessment in northern Italy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4401, https://doi.org/10.5194/egusphere-egu23-4401, 2023.

A storyline is defined as a physically self-consistent unfolding of past events or of plausible possible futures (Shepherd et al., 2018). It has advantages in effective risk communication and adaption, as it moves the emphasis away from probability across to plausibility (Butler et al., 2020). Working as part of the EvoFlood (Quantifying the Evolution of Flood hazard and risk across a changing world) project, this work presents a novel methodology for estimating future hydrology based on not only climatic drivers, but the wider impacts of dams, river regulation and changing land-use. Grounded in historical atmospheric river floods, storylines are extracted from the large ensemble reforecast dataset provided by the Global Flood Awareness System (GloFAS; http://www.globalfloods.eu/).

Butler, J. R. A., Bergseng, A. M., Bohensky, E., Pedde, S., Aitkenhead, M., & Hamden, R. (2020). Adapting scenarios for climate adaptation: Practitioners’ perspectives on a popular planning method. Environmental Science & Policy, 104, 13–19. https://doi.org/10.1016/j.envsci.2019.10.014

Shepherd, T. G., Boyd, E., Calel, R. A., Chapman, S. C., Dessai, S., Dima-West, I. M., Fowler, H. J., James, R., Maraun, D., Martius, O., Senior, C. A., Sobel, A. H., Stainforth, D. A., Tett, S. F. B., Trenberth, K. E., van den Hurk, B. J. J. M., Watkins, N. W., Wilby, R. L., & Zenghelis, D. A. (2018). Storylines: An alternative approach to representing uncertainty in physical aspects of climate change. Climatic Change, 151(3–4), 555–571. https://doi.org/10.1007/s10584-018-2317-9

How to cite: Griffith, H. and Cloke, H.: Building Storylines of Future Atmospheric River Floods, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17254, https://doi.org/10.5194/egusphere-egu23-17254, 2023.

Convective rainfall cells have a maximum prediction time of 30 to 120 minutes, which means that physically based models are usually too slow to calculate the expected flooding depths within the available time. For this reason, novel models for short-term flood and flash flood prediction are needed.

The work is being carried out as part of the WaX program and its aim is to develop a fast flood prediction model for temporal and spatial precipitation data (for example high-resolution radar forecast) and runoff-relevant soil parameters with machine learning methods for catchments with strong topography.

The developed AI model aims to predict maximum flood depths for an urban catchment (Emmendingen in Baden-Württemberg, Germany) and temporally resolved flood depths in predefined neuralgic areas. It is based on supervised learning and therefore requires a database of input and associated output for training and validation.

The effective rainfall, which is based on spatially and temporally distributed rainfall (from radar hindcast) and runoff-relevant parameters such as land use, slope, soil type and especially soil moisture, serves as the training input. The associated results for training and validation are the spatially distributed flood depth within the catchment. To build up the database both, the flood depths and effective rainfall rates, were precalculated using established hydrological respectively hydrodynamic models. To predict flood depths during real heavy rainfall events, a number of different high-resolution radar forecasts are used and combined with a range of soil moisture assumptions.

The model is a combined method, in which the hydrological processes are done by a fast and calibrated physically based model, while the time-consuming hydrodynamic calculation is replaced by machine learning methods. This leads to a utilization of the low calculation time in the range of seconds with promising accuracy compared to the results from hydrodynamic simulations. Due to the fast prognosis time it is possible to calculate a series of ensembles for different soil moisture conditions and precipitation loads as a result of the uncertain soil moisture conditions and the uncertain radar forecast. The contribution will compare preliminary AI model predictions to the physically based model results to assess the potential and limitations of the model.

How to cite: Reinecke, A. and Neuweiler, I.: Development of a flood prediction model for heavy rainfall based on spatially and temporally distributed precipitation using machine learning techniques, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13714, https://doi.org/10.5194/egusphere-egu23-13714, 2023.

The combined impacts of climate change and anthropogenic activities have altered runoff generation and flood regime in many regions, worldwide.  While hydraulic structures have been successfully operated to control flood for decades, their expected performance may be currently less certain under the augmented frequency of extreme precipitation events. The goal of this study was to examine the above hypothesis by utilizing both remote sensing and field data on the Imamzadeh Davood catchment in the northern Iran, which experienced a devastating flash flood in the summer of 2022. To this end, we surveyed the main river path to collect data on river morphology, structural characteristics of check dams, and sedimentation patterns. We also processed satellite imagery to extract and temporally trace back land-use land-cover change in the study area. Finally, we used recorded data from synoptic stations to explore the distinct role of extreme precipitation in intensifying the flood hazard. The results proved the occurrence of unprecedented precipitation with a return period of over 100 years, supporting the climate change effect in the region. In-situ observations revealed that all 18 check dams were destroyed between 20% and 100% during the flood event, while higher degree of destruction was observed towards upstream. The sliding and overturning stability analysis demonstrated that all check dams were stable with respect to sliding, while 30% of them were prone to overturning. Given the destruction of all check dams during the flood event, as well as the observed high deposition depth of sediment in the river corridor, we concluded that the shock imposed by the debris flow was responsible for the cascade failure of check dams from upstream to downstream. The findings of this study highlight the need for revisiting the design principles of hydraulic structures, such that they are adapted to the ongoing impacts of climate change in order to increase the resiliency of flood control systems.

How to cite: Hosseinipoor, M., Mollaei Rudsary, A., Yeganeh, Y., Kazempour, Z., and Danesh-Yazdi, M.: Why should structural solutions for flood control be adapted to climate change?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2281, https://doi.org/10.5194/egusphere-egu23-2281, 2023.

The Chalk is considered an important aquifer in the Southeast of the UK as it supports flows in ecologically sensitive Chalk streams, as well as significant groundwater abstractions for public water supply purposes. Based on the Water Framework Directive (EU directive) objectives, all rivers need to be in good ecological status or support good ecological potential by 2027. The environmental regulatory body (Environment Agency) have designated the area located Northwest of London as over-licensed and over-abstracted in terms of groundwater availability from the Chalk aquifer. As a result of this, a long-term management strategy has been proposed, allowing for significant groundwater abstraction reductions for implementation between now and 2050.

Whilst under a range of river flow conditions, the proposed abstraction reductions are expected to allow greater baseflow to enter the rivers, it is possible that under higher flow conditions there will be an elevated risk of flooding, especially in downstream locations. An alternative approach is presented in this case study near London, aiming to utilise the well-established river-aquifer interactions during a range of hydrological conditions to balance the effects of winter floods and low flows during droughts.

The proposal for this case study is in an unconfined Chalk aquifer setting, supporting a number of groundwater abstractions, as well as providing baseflow to a river which is also supported by an effluent discharge. A nearby surface water reservoir located on top of clay deposits, is also available but currently unused for public water supply. Groundwater abstractions in the area are known to be supported by river flows during drought conditions, via a leaky river bed. Based on river bed leakage assessments undertaken under different hydrological conditions, it was found that a certain proportion of the total river flow can recharge the unconfined chalk aquifer via the leaky river bed in a 2-3 km stretch of river.

Therefore, the idea of capturing high river flows above a certain trigger at a downstream location through the urban areas where the river is in a concrete channel and refilling the currently disused reservoir storage, has been explored. Instead of then having to treat this water as surface water before using it for public water supply, by releasing this water back into the river at the head of the catchment during times of low flows it could support both river flows and also the output of the groundwater sources via artificial leakage. This unconventional type of Managed Aquifer Recharge has been tested under various hydrological conditions and could also prove a cost-effective scheme due to the lack of additional treatment needed for the surface-derived water.

This study demonstrates that enhanced understanding of the natural processes in a river catchment can provide alternative ways of managing the effects arising from both flood and drought events, whilst creating a resilient water supply in a changing climate.

How to cite: Karapanos, I. and Powers, E.: Innovative approaches to water resources management during flood and drought periods using semi-natural processes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2677, https://doi.org/10.5194/egusphere-egu23-2677, 2023.

The potential of healthy ecosystems in providing a multi-purpose and sustainable approach to Disaster Risk Reduction (DRR) and Climate Change Adaptation is widely acknowledged and, e.g., also highlighted in the latest Adaptation Strategy of the European Commission. However, to what extent an ecosystem can support DRR is largely determined by its condition. This holds also true for forest ecosystems. Their potential in supporting water retention and, therefore, in reducing drought and flood risk is widely recognized. However, often their potential to retain water is impaired by many stressors. Many of them are related directly to the trade-offs that come along with the forest management objectives. This is particularly the case when the ecosystem management’s target is to maximize the provision of one Ecosystem Service (ES), such as the provision of timber, which often leads to a considerable decline in the ecosystem’s ability to provide other ES, such as water retention. In alpine regions exists, for example, the concept of protective forests where financial interests in timber production are subordinate to address the trade-offs between forest ES. However, this concept has not received much attention in low mountain ranges so far even though they can already cause considerable orographic precipitation. 

Within this study, we investigated possible challenges and approaches for increased implementation of water retentive forest management in low mountain ranges. This was exemplarily done for the Rhineland-Palatinate part of the Ahr catchment. 19 investigative semi-structured expert interviews were conducted with 20 actors from the forestry, water, and nature conservations sector which included practitioners, academics, and personnel in higher and lower administrative levels and advisory centers. The qualitative analysis of the interviews has shown that the extreme 2021 floods (return period at minimum 500 years) were a warning shot that sparked interest in the water retention potential of forests at various levels, which was before majorly in the focus to reduce the drought risk on forests. However, several interacting barriers exist, ranging from rather silvicultural to socio-structural challenges. As reported by other research, a key challenge was related to finance. For example, the clearance of dead spruce stands is often financially motivated. However, research shows that this impairs the forest’s water retention capacity. Furthermore, a financial bottleneck was observed regarding infrastructural adaptations for enhanced water retention. Our work shows that due to the various potential co-benefits water retention measures in the forest can potentially profit from different funding mechanisms. Especially from the water sector, funding opportunities are available for measures that might not be covered under current funding schemes from the forest sector. However, a key prerequisite is that observed compound and cascading interactions are addressed. The limited cooperation between the different actors should be enhanced in this regard which will require improved coordination from the respective higher authorities and greater awareness locally.

How to cite: Rackelmann, F., Bell, R., and Sebesvari, Z.: Challenges to and approaches for water retentive forest management in low mountain ranges in Germany, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10897, https://doi.org/10.5194/egusphere-egu23-10897, 2023.