PICO
Recent research has marked an interesting step forward in our knowledge of floods, the way they occur and hit communities, and our capability to predict them. New data availability and the advent of new methods, notably those based on artificial intelligence, convey exciting perspective to cope with floods in the future. At the same time, new solutions are emerging, spanning from nature based ones to structural and infrastructural interventions.
On the other hand, there is growing and data-based evidence that flood risk, in terms of expected damage is increasing. It is also increasingly clear that often floods take communities by surprise. The number of truly unexpected events that are continuously occurring is concerning. Therefore, we assist to a sort of paradox, where new knowledge and opportunities are associated to an increase of risk. What are the reasons for this paradox? For what reason we are not able to transfer new knowledge into operational practice to mitigate the risk of flood? These are interesting questions that are rooted into the science of floods and the way local and regional communities and civil protection manage the risk of flood and its implications.
From a scientific point of view, it is not yet clear the dynamic interaction between climate change, hydrological change (including land-use change) and societal changes. It is also not clear what is the reason of the above surprise. As a result, we are still not fully capable of identifying priorities for actions and solutions.
This talk aim to propose a closer look at the above paradox and questions, basing on the assumption that floods never occur for one reason only, but rather from an interaction of drivers. These need to be better explored by promoting an interdisciplinary approach, which hopefully will promote a transdisciplinary transformation. I will look at the key role of society and in particular economy to get to target and I will discuss the perspectives given by artificial intelligence, which is not a new opportunity but is becoming dramatically more accessible thus offering new options.
The case of the Po River, in Italy, will be used as an example case study, by emphasising that flood risk is not an isolated problem, but it is often accompanied by hydrological risk in general and in particular the risk of drought. Therefore, finding solutions need to be a synergetic effort.
How to cite: Montanari, A.: A closer look at flood risk and future perspectives after changes in climate, hydrology and society, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4731, https://doi.org/10.5194/egusphere-egu25-4731, 2025.
High Mountain Asia (HMA) faces significant hydrological and geomorphic challenges due to global warming and cryosphere loss, which are altering water supply patterns and the frequency of flood hazards such as glacial lake outburst floods (GLOFs) and landslide-dammed lake outburst floods (LLOFs). These floods have historically caused significant damage, destroying many hydropower projects (HPPs), including major events in 1981, 1985, 2016, and 2018. While reservoirs with large storage capacities can mitigate some impacts, many planned and existing HPPs remain vulnerable. Here we compile a new flood database between 1950 and 2023 in HMA. A total of 1,015 flood events are documented, including 261 pluvial floods (PFs), 220 snowmelt-induced floods (SFs), 427 GLOFs, and 107 LLOFs. The changing flood frequency is linked to warming temperatures, rising precipitation, and cascading interactions with glaciers, permafrost, and human exposure.
Floods threaten infrastructure, disrupt energy production, and mobilize sediments that degrade reservoirs and turbines, intensifying risks under ongoing climate change. However, strategic design, maintenance, and sediment management, supported by improved monitoring and early warning systems, can enhance the resilience of hydropower projects. Policymakers and stakeholders must urgently adopt sustainable strategies to address these flood hazards, ensuring the viability of hydropower and contributing to sustainable development in this critical region.
How to cite: Li, D., Ni, J., Lu, X., Walling, D., Lane, S., Steiner, J., Immerzeel, W., and Bolch, T.: Climate and geomorphic-driven river floods and related impacts on hydropower in High Mountain Asia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1860, https://doi.org/10.5194/egusphere-egu25-1860, 2025.
The Himalayan rivers of India exhibit certain unique characteristics as they undergo large seasonal fluctuations in their water regime. During the monsoon months, these rivers experience a soaring flow of water due to excessive rainfall and the melting of glaciers, often resulting in recurring floods in the plains. In addition to high flows, these rivers carry heavy sediment loads, which make the riverbanks vulnerable to erosion. The Brahmaputra, one of the largest rivers in India, is often associated with devastating floods in the state of Assam. Since the great earthquake of 1950, which struck the Upper Brahmaputra Valley in Assam, riverbank erosion has become a scourge for the land and its people. After the earthquake, the problems of flooding and riverbank erosion have intensified in the valley. Majuli, the largest and one of the most populous freshwater riverine islands in the world, as well as a proposed UNESCO cultural heritage site, has experienced significant morphological changes due to the continuous shifting of the river channels of the Brahmaputra and its tributaries. Thus, the study aims to understand the morphological dynamics of the Brahmaputra River over the last five decades by employing statistical indices such as the Plan Form Index (PFI), Braiding Index (B.I.), and Migration Index (M.I.). The PFI values indicate the degree of braiding in a river, with values below 4 indicating a highly braided channel, between 4 and 19 indicating a moderately braided channel, and above 19 indicating a low braided channel. The study shows that the PFI value for the Brahmaputra near Majuli decreased from 7.73 in 1975 to 4.29 in 2000, and further declined to 3.54 in 2024, indicating an increasingly braided nature. Similarly, Brice’s Braiding Index (B.I.) reflects a similar trend, rising from 4.31 in 1975 to 5.22 in 2020, and further to 5.49 in 2024. The Migration Index (M.I.) of the river increased from 0.885 for the period 1975–2000 to 0.909 for the period 2000–2024, highlighting a highly unstable river with frequent bank failures. It is important to note that as per the Census of India, the total area of Majuli Island was 1,246 km² in 1951. However, the present study indicates a significant reduction in the island's area, measuring 629 km² in 1975, 601 km² in 2000, and 487 km² in 2024 respectively. This indicates a loss of nearly two-thirds of the island's original area, with 107 out of 210 cadastral villages being engulfed by the river over the last 70 years. Thus, the study highlights the urgent need for both structural and non-structural measures to protect Majuli Island from further erosion by the Brahmaputra and its tributaries.
Keywords: River Brahmaputra, Morphology, Majuli Island, Erosion, Plan Form Index, Braiding Index, Migration Index
How to cite: Roy, N.: Fluvial Morphodynamics of the River Brahmaputra and its Implications on the Majuli Island, India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-815, https://doi.org/10.5194/egusphere-egu25-815, 2025.
Aggradation in the Waiho River has been the subject of research for over 40 years (e.g. Mosley, 1983; Hoey, 1990; Davies, 1997; Davies et al., 2003). Where the Waiho emerges from confinement at the Southern Alps rangefront it has formed a large alluvial fan. Development on this fan in the form of the Franz Josef / Waiau tourist township, State Highway 6 and its bridges, and pastoral agriculture has resulted in artificial confinement of the active portion of this fan, principally using stopbanks (flood walls / artificial levees). Unable to distribute its bedload across the fan surface, the river has responded by aggrading its bed. In turn, stopbanks have been raised regularly, perching the river, which now sits ~2 m above the level of the township, elevating flood risk. Application of Geomorphic Change Detection (GCD) using LiDAR surveys acquired in 2016, 2019, 2023, January 2024 and July 2024 demonstrate a remarkable rate of aggradation equating to 0.2 m yr-1 in the vicinity of the township, that appears to have been ongoing since about 1960. A combination of recent storms and glacier retreat appears to have increased sediment delivery in the Waiho proximal to the Franz Josef Glacier. GCD analysis reveals that sediment is being pulsed through to the Waiho Fan through this relatively confined proglacial reach. On the fan, an avulsion has cut through to the adjacent Tatare River to the north, which is now rapidly infilling with bed calibre material. As the avulsion incises, more flow is captured and a full switching of the Waiho into the Tatare is a possibility.
The situation is complicated by the high probability (75% in 50 years) of an extreme earthquake in the area, that will damage stopbanks and severely aggravate aggradation over years to decades. This event is so likely that all but short-term flood risk management strategies must consider it. These significant flood and avulsion hazards pose extreme risk to life and property in the vicinity of Franz Josef / Waiau and are in urgent need of mitigation. The current management practice of raising stopbanks and repairing rock-lined edges is setting the system up for catastrophic failure given the rates of change we observe. A ten-year programme allowing for managed retreat and release of the Waiho to the south is proposed. It is anticipated that this will reduce the rate of current riverbed aggradation and allow a staged relocation of the township in the longer term.
References
Davies, T. (1997). Long-term management of facilities on an active alluvial fan - Waiho River Fan, Westland, New Zealand. Journal of Hydrology (NZ), 36, 127–145.
Davies, T., McSaveney, M., Clarkson, P. (2003). Anthropic aggradation of the Waiho River, Westland, New Zealand: microscale modelling. Earth Surface Processes & Landforms, 28, 209-218.
Hoey, T. (1990). Aggradation in the Waiho River. Final Report to the West Coast Regional Council, 23p.
Mosley, M.P. (1983). Response of the Waiho River to variations in Franz Josef Glacier, Westland, New Zealand. Internal Report WS 858, Hydrology Centre, Christchurch, NZ, 17p.
How to cite: Fuller, I., Beagley, R., Davies, T., Gardner, M., Healey, M., and Williams, G.: Managing geomorphological drivers of river hazards in the rapidly aggrading Waiho River, Franz Josef / Waiau, Aotearoa New Zealand, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1366, https://doi.org/10.5194/egusphere-egu25-1366, 2025.
The Mekong River–Tonle Sap Lake interaction system plays a vital role in supporting livelihoods in the region through the reverse flow phenomenon. During the flood season, a substantial volume of water flows from the Mekong mainstream into the Tonle Sap Lake floodplain, which is then gradually drained during the dry season to provide additional water to the Vietnamese Delta. This interaction is critical for fisheries and agriculture, benefiting approximately 20 million residents across the Tonle Sap Lake and Mekong Delta regions.
However, since 2010, extensive dam construction in the upper Mekong River and local sand mining activities have significantly altered the flow regime, weakening the interaction in two key aspects: the duration of reverse flow and the volume of nutrient-sediment water entering the lake. Utilizing an integrated modeling framework comprising hydrodynamic and hydrological models, this study found that while the Tonle Sap Lake system demonstrated resilience to climate change between 2010 and 2024, the influence of human interventions has been profound.
Our results indicate that the average annual reverse flow volume, which was approximately 43 km³ during the historical period (1980–2000), has declined by about 25% to an average of 30 km³ in recent years. Additionally, the duration of the reverse flow has shortened by approximately 20 days. These changes underscore the dominant role of anthropogenic stressors in disrupting the Mekong River–Tonle Sap Lake system.
To sustain this critical interaction, urgent measures are needed to regulate local sand mining and foster transboundary collaboration with upstream states regarding dam operations and future reservoir construction. Such actions are essential to maintaining flow regimes that approximate natural conditions and securing the livelihoods of millions in the region.
How to cite: Morovati, K. and Tian, F.: Impacts of Climate Change, Sand Mining, and Hydropower Dams on the Mekong River–Tonle Sap Lake Interaction System, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2407, https://doi.org/10.5194/egusphere-egu25-2407, 2025.
Vegetation effects are particularly significant in dryland region channels, where flooding is mainly as flash floods, because large vegetation commonly grows within the channels. Measurements at long-term study sites in ephemeral channels of southeast Spain show that such vegetation can be highly resilient to a range of flows. However, extreme events, such as occurred in September 2012, can effectively zero the vegetation in the channels and valley floor. The effects of the vegetation in mature pre-flood and in sparse post-flood state on the hydraulics of flow and on flood levels have been measured in the field and calculated using a range of assumptions on roughness effects. The vegetation state is shown to have large effects on flow velocities and on flood stage and inundation extent. Since that extreme event the recovery of vegetation has been measured annually. Differential rates of recovery are evident between sites and within sites, varying with spatial position in relation to the main channel. In some locations vegetation has regrown to pre-2012 states but elsewhere occurrence of a series of moderate to large flows has restricted growth. Drought conditions have also occurred over the past decade and in earlier periods, affecting growth. The vegetation dynamics have complex interactions with the sediment and morphological changes in these channels and together they contribute to variations in flood capacity and hydraulics of flow. Feedback effects through erosion and deposition processes are identified. Results of modelling the effects of the different vegetation coverage, assemblages and heights of plants are discussed. Effects of timing of flows and of hydrological balances, countered by extreme temperatures, are analysed. It is shown that the dynamics of vegetation, through succession of different size events and varying conditions, have a significant effect on flood levels and spatial patterns in ephemeral channels and these need to be incorporated in flood modelling and predictions. Consideration of flood management strategies needs to recognise that presence and dynamics of vegetation can pose both challenges and benefits, especially in highly erodible catchments with very high sediment fluxes and under conditions of climate change.
How to cite: Hooke, J.: Mediation of hydro-geomorphological process effects on flooding by vegetation in dryland channels , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3099, https://doi.org/10.5194/egusphere-egu25-3099, 2025.
Compound flooding refers to the co-occurrence of multiple flooding mechanisms, leading to more severe and complex flood events. Low-lying coastal deltas and estuaries are especially prone to compound flooding as they face multiple drivers such as storm surges, high river discharge, intense rainfall, tides, and sea-level rise. These combined sources amplify the impacts, resulting in significant loss of life and property, as seen in Hurricane Katrina (New Orleans, 2005), Cyclone Nargis (Myanmar, 2008), and Storm Xynthia (French Atlantic coast, 2010). Globally, 2.15 billion people live in near-coastal areas, including 898 million in low-elevation coastal zones. The UK has a long history of estuarine flooding caused by compound events. Climate projections suggest hotter, drier summers and wetter winters, accompanied by more frequent and intense extreme events. Sea-level rise is expected to exacerbate vulnerabilities in the UK's coastal regions (UK Met Office, IPCC 2014). Coastal aquifers are frequently affected by flooding, making groundwater a critical factor in estuarine geomorphology. Recent studies have highlighted the significant volumetric and chemical importance of groundwater in river-dominated coastal systems, warranting further investigation under climate change scenarios.
In this study we have developed a coupled catchment and groundwater model using Caesar Lisflood to assess groundwater’s contribution to compound flood events. The model is calibrated using historical fluvial and tidal flow data to evaluate how river discharge, groundwater, and associated drivers shape flood magnitude, timing, and behavior. Additionally, the study analyzes the sensitivity of the estuary to changes in hydrogeological parameters by observing variations in modeled groundwater heads and simulated discharge in response to changes in aquifer properties. Our research focuses on the Conwy estuary in North Wales, a flashy catchment that experiences frequent flooding events. A notable compound flood occurred during Storm Ciara (February 2020), when record river levels, intense rainfall, and high storm tides combined to affect 172 properties. The Conwy River drains a 600 km² catchment with annual precipitation averaging 1,700 mm and a baseflow contribution of 27%. Baseflow, the component of streamflow discharged from groundwater storage, reacts slowly to rainfall and is notably influenced by topography, geology, vegetation, land use, and climatic factors. This research delves into the lesser-studied role of groundwater in estuarine hydrology, providing insights into its potential impact on compound flood dynamics under future climate scenarios.
How to cite: Bhattacharya, A.: Impact of Groundwater in Compound Flooding: A Case Study of the Conwy Estuary in Wales., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7245, https://doi.org/10.5194/egusphere-egu25-7245, 2025.
Abstract
Nature-based solutions in coastal ecosystems offer more efficient and sustainable strategies to cope with climate changes and anthropogenic modifications compared to traditional hard engineering measures. In river deltas, managed realignment through levee breaching has become an increasingly common approach for restoring coastal wetlands and reestablishing natural depositional dynamics on previously reclaimed deltaic plains.
This study focuses on the formation of new wetlands in the Po River Delta (PRD) following dyke failures over the last 3 decades. During this period, portions of reclaimed land in the delta's most seaward sector were abandoned, flooded, and progressively transformed into vegetated wetlands.
Our study area, known as "Batteria" Island, is located in the PRD northeastern portion. Previously used as agricultural land dedicated to rice cultivation, the area was partially abandoned following significant subsidence and a series of large floods from the Po River during the 1970s. These floods caused widespread inundation by seawater and induced soil salinization. Subsequently, the area, left flooded, was utilized both as a hunting reserve and a fish farm before being permanently abandoned between the 1980s-1990s. The lack of maintenance led to the failure of several artificial dykes, ranging in height from approximately 1 to 3 meters, allowing river waters to inundate previously reclaimed, low-lying deltaic land. One of these dyke breaches, which occurred in 1999, resulted in the formation of approximately 30 hectares of new wetlands in less than 20 years.
In this study, we utilized a depth-averaged, coupled hydro-morphodynamic and sediment transport model to simulate wetland formation at Batteria Island. The numerical model was applied to an unstructured grid representing the entire PRD and was forced by 30 years of mean high-water levels and peak river discharge at the downstream and upstream boundaries, respectively. The model also incorporated a steady subsidence rate of 2 cm/year, derived from empirical data.
The model successfully reproduced wetland formation following dyke breaching, aligning with observations from aerial photos and bathymetric surveys. Consequently, we applied the same model to simulate dyke breaches at different locations within the PRD to evaluate the feasibility of using managed realignment to create new wetland areas of significant socio-economic and ecosystem value.
Our study highlights the inherent ability of highly anthropized river delta systems—characterized by extensive reclaimed land—to retain sediment and build new land when dykes are removed, whether naturally or artificially. This process enables these systems to recover a more natural, dynamic state, characterized by rapid and widespread wetland formation. Such a transformation enhances resilience to projected relative sea-level rise in the near future.
Keywords: Nature-based solutions, Burcio lagoon, Levee Breaching, Morphodynamic model, 2DEF, Shallow water area
How to cite: Shamsnia, S. H., Finotello, A., Pietro Viero, D., Carniello, L., D'Alpos, A., Ghinassi, M., and Marzia Rossi, V.: Modeling Wetland Rebuilding After Dyke Failure in Highly Anthropized River Deltas: A Case Study from the Po River Delta, Italy, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9122, https://doi.org/10.5194/egusphere-egu25-9122, 2025.
Extreme flood events can cause significant geomorphic changes in river systems, including bank erosion, sediment deposition, river braiding and the formation of new channels, resulting in extensive damage to settlements, infrastructure, and floodplain structures. At the same time, information on the extent, nature and distribution of the geomorphologic impacts of floods is often not systematically collected and is therefore not available to assess the consequences of flood events and associated risks, or to provide a basis for efficient water management and flood protection.
This study presents longitudinal research employing geomorphologic mapping and UAV photogrammetric reconstructions to track the intensity, type, and distribution of geomorphic changes to streams in the Opava River Basin, Jeseníky Mts., Central Europe, recurrently affected by devastating floods. The field survey was carried out repeatedly in the area after major floods in 1997, 2007, and 2024 using a consistent mapping methodology. This approach combined the mapping of geomorphologic flood effects with hydromorphological properties, including information on channel and floodplain modifications. The survey covered a contiguous stretch of river in the core flood zone over a length of 100 km, and the UAV campaigns following the 2024 flood focused on selected river segments representing hotspots of river dynamics.
The large-scale mapping results allowed for an assessment of the spatial distribution of flood effects, the identification of critical elements and structures, and the analysis of relationships between stream modifications and the nature of geomorphic impacts. High-resolution models from UAV monitoring allowed us to quantify detailed geomorphic analysis and determine bank erosion rates, sediment volumes, and channel migration patterns.
The analysis revealed substantial spatial variability in geomorphic responses, with particularly intense erosion and sediment deposition observed in narrow valley sections and areas of high flow velocity, as well as in relation to floodplain connectivity and channel modifications. The most significant geomorphological changes consistently reoccurred in the same locations, signaling the need for targeted river management and protection.
The study highlights the importance of geomorphic mapping of flood impacts for understanding the risks posed by high-intensity floods, improving risk assessment, and efficient post-flood recovery efforts. Methodologically, it emphasizes the efficiency of UAV photogrammetry for detailed and rapid post-flood assessments, providing comprehensive information to better understand flood dynamics and target river management strategies.
How to cite: Langhammer, J. and Lehký, M.: Geomorphological Response of Montane Streams to Extreme Floods, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9823, https://doi.org/10.5194/egusphere-egu25-9823, 2025.
Flood risk is increasing worldwide, however, studies on river geomorphological responses to floods often lack explicit consideration of anthropogenic impacts on rivers. A pervasive impact of human modification has been the conversion of anabranching riverscapes to incised, single thread, so called ‘fire-hose’ channels. However, the consequences of such modification for river functioning are poorly understood, restricting our ability to manage flood risk in modified systems or restore these riverscapes. Therefore, we aim to determine how incision of gravel bed rivers modifies their geomorphological response to flood events. We undertook an experiment in a large hydraulic flume, designed to simulate an alluvial gravel-bed river. The flume was filled with loose sand and seeded with alfalfa to represent riparian vegetation. Under our initial conditions of low flow and sediment input, a fully equilibrium anabranching channel developed. Subsequently, we simulated both small and large flood events. We then prompted incision by lowering the downstream base level, allowed the channel to reach a new equilibrium state, and conducted the same flood sequence. We compare the response of the anabranching and incised treatments to floods, in terms of geomorphic work done, morphological response and sediment output. First, we found that for the same input conditions, both anabranching and incised, single thread, equilibrium states existed, determined by the historical changes in base level modification. However, the two equilibrium states responded very differently to flood events. Riparian vegetation played a critical role in this process, reducing widening and channel migration associated with incision in non-vegetated experiments. Instead, channel morphological changes to high flows after incision were predominantly through adjustments to river depth. Second, incision reduced flooding because even the largest flows were fully contained within the channel. However, sediment export from the incised channel during floods was nearly double that of the anabranching treatment. Consequently, incision reduced flood extents locally, but may exacerbate flood risk overall by transporting water quickly downstream and exporting much greater amounts of sediment which could reduce channel capacity at other parts of the river network.
How to cite: Mason, R., Delorme, P., Murphy, B., McLelland, S., Baynes, E., Polvi, L., Rice, S., and Parsons, D.: Effect of incision on river response to floods: Insights from flume experiments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15572, https://doi.org/10.5194/egusphere-egu25-15572, 2025.
Rivers need space to sustain key ecological and geomorphological functions, and to convey floodwater. However, river management efforts have often used structural engineering approaches to mitigate erosion hazards to land that has been developed for agricultural, industrial and urban land uses. In the Philippines, current easement regulations require a minimum 3 metre buffer along the bank of a river for urban areas and 20 metre buffer for agricultural lands. We use a four-decade long archive of satellite imagery, processed in Google Earth Engine, to investigate river mobility across the Philippines, enabling us to quantify how mobile rivers are and the land covers that are eroded due to river migration. In more detail, our study assesses Land Use and Land Cover (LULC) changes and river mobility across ten catchments using national-scale LULC datasets (2003, 2010, 2015, and 2020) and satellite imagery from 1988 to 2021. We standardised LULC classifications and analysed transitions within catchments, identifying key changes in dominant land cover types. Intersections between active channel edges and LULC maps revealed the types of land cover rivers interacted with over time, highlighting areas of encroachment and potential risk. Using Digital Shoreline Analysis Software, we quantified river migration rates between 2000 and 2020, along each river, identifying spatial patterns of river movement and areas where rivers migrated into new LULC types. The analysis of LULC distributions at varying distances from the maximum active channel extent provides insights into how easement regulations could be informed by observations of actual river mobility. Our findings are a demonstration of a nature-based solution to defining how much space rivers need, informed by big data. The findings have direct implications for Philippine easement laws, which mandate buffer zones along waterways to protect against flood and erosion risks, and environmental degradation; there is potential to re-evaluate static buffer zones and consider adaptive, risk-based approaches to easement enforcement.
How to cite: Tolentino, P. L., Boothroyd, R., McDonnell, C., and Williams, R.: Interactions between river mobility and land use in the Philippines: implications for space to move policies, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17644, https://doi.org/10.5194/egusphere-egu25-17644, 2025.
In recent years, significant advancements in geomorphic methods have offered a cost-effective and valuable alternative for large-scale flood mapping. Among these, the Geomorphic Flood Index (GFI) has gained widespread adoption for flood delineation applications globally (Samela et al., 2017). The development of the GFA-tool plug-in for QGIS has helped to disseminate and simplify the application of this approach and boosted its popularity (Samela et al., 2018).
The GFI builds on Digital Elevation Models (DEMs) information on water levels in each drainage network cell and elevation differences between each river basin location and the closest stream channel cell hydrologically connected to it. However, in its current original formulation, certain limitations exist that can affect its usability and reliability (Albertini et al., 2021). In fact, near confluences, floodwater may not strictly follow river connectivity patterns and secondary tributary floodplains may be partially submerged due to the backflow from the mainstream.
To address these challenges, a new methodology has been developed that explicitly takes into consideration confluences. This improved approach enhances the robustness of the index and provides more reliable flood mapping, even in complex settings such as large alluvial valleys. The method further improves the reliability of flood depth estimations obtained through this approach.
References:
Albertini, C., D. Miglino, V. Iacobellis, F. De Paola, S. Manfreda, Flood-prone areas delineation in coastal regions using the Geomorphic Flood Index, Journal of Flood Risk Management, e12766, 2021.
Samela, C., R. Albano, A. Sole, S. Manfreda, A GIS tool for cost-effective delineation of flood-prone areas, Computers, Environment and Urban Systems, 70, 43-52, 2018.
Samela, C., T.J. Troy, S. Manfreda, Geomorphic classifiers for flood-prone areas delineation for data-scarce environments, Advances in Water Resources, 102, 13-28, 2017.
How to cite: Manfreda, S., Saavedra, J., Albertini, C., Pacia, D., Samela, C., and Zhuang, R.: Geomorphic Flood Index 2.0: Enhanced Tools for Delineating Flood-Prone Areas in Data-Scarce Regions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18999, https://doi.org/10.5194/egusphere-egu25-18999, 2025.
