Autumn Floods Research Articles

Материковый сток в Кандалакшский залив Белого моря с Карельского берега в теплый сезон года (с конца весеннего паводка до осеннего половодья

In order to determine the flow of fresh water from the Karelian coast in the warm season, in 2018–2023. Seasonal observations of water flow were carried out in watercourses flowing into the Chupa, Medvezhya, Kiv, Keret and Letnyaya bays of the Kandalaksha Bay of the White Sea. In rivers and streams, changes in water flow per day were studied, starting from the end of the spring flood to the end of the autumn flood. It was revealed that river water flow in the warm season of the year from this part of the Karelian coast does not exceed 750 million m3, and stream flow – 60 million m3. Seasonal water flow has two maximums (end of May–first ten days of June and end of September–mid-October) separated by a summer low-water period. Despite the length of the summer low-water period, its share in the total seasonal runoff does not exceed 40 % (on average 34±1 %). Over the course of 6 years, the volume of stream flow in this part of the Karelian coast increased on average by 2–3 % per year, and river flow by 1–2 % per year. Two years with a low total seasonal runoff (2018 and 2022) and two years with an increased total seasonal runoff (2021 and 2023) are distinguished. The data obtained indicate that freshwater runoff from the Karelian coast to the waters of the White Sea is subject to cyclical nature with a slight increase in the total volume of continental runoff.

Water budgets in an arid and alpine permafrost basin: Observations from the High Mountain Asia

Ground freeze‒thaw processes have significant impacts on infiltration, runoff and evapotranspiration. However, there are still critical knowledge gaps in understanding of hydrological processes in permafrost regions, especially of the interactions among permafrost, ecology, and hydrology. In this study, an alpine permafrost basin on the northeastern Qinghai‒Tibet Plateau was selected to conduct hydrological and meteorological observations. We analyzed the annual variations in runoff, precipitation, evapotranspiration, and changes in water storage, as well as the mechanisms for runoff generation in the basin from May 2014 to December 2015. The annual flow curve in the basin exhibited peaks both in spring and autumn floods. The high ratio of evapotranspiration to annual precipitation (>1.0) in the investigated wetland is mainly due to the considerably underestimated ‘observed’ precipitation caused by the wind-induced instrumental error and the neglect of snow sublimation. The stream flow from early May to late October probably came from the lateral discharge of subsurface flow in alpine wetlands. This study can provide data support and validation for hydrological model simulation and prediction, as well as water resource assessment, in the upper Yellow River Basin, especially for the headwater area. The results also provide case support for permafrost hydrology modeling in ungauged or poorly gauged watersheds in the High Mountain Asia.

The phenology of Eucalyptus camaldulensis (Dehnh, 1832) and Eucalyptus coolabah (Blakely & Jacobs, 1934) in the northern Murray–Darling Basin and implications for recruitment on floodplains

Context Published evidence suggests recruitment of floodplain trees is declining in the northern Murray–Darling Basin (MDB) and that this is linked to river flow. Aims We investigated the reproductive phenology of Eucalyptus camaldulensis and Eucalyptus coolabah to better understand tree reproductive cycles and the influence of rainfall and flow on seed production. Methods We surveyed phenological events (bud, flower and fruit production) over 6 years, at nine sites along the Condamine–Balonne River and examined correlations between these events and meteorological parameters. Key results For both species, event timing was consistent across sites and years and event relative abundance scores were different between years. Bud abundance was correlated with rainfall, flooding and warming temperatures and E. coolabah produced additional bud crops after floods. Conclusions The timing of events did not differ significantly from published results for the southern MDB. Rainfall, river flows and flooding in spring resulted in more abundant bud crops in E. camaldulensis and E. coolabah, and subsequently more abundant fruit crops. Fruit dehiscence coincided with summer–autumn flooding, which provides seed for germination. Genetic and physiological factors may also influence the observed pattern. Implications These results will inform water planning in Queensland, Commonwealth Environmental Water Holder watering actions and long-term watering plans in the northern MDB.

Coastal ecological disasters triggered by an extreme rainfall event thousands of kilometers inland

The world is experiencing an increase in the frequency and intensity of extreme weather events, yet the influences of remote inland extreme weather events on the coastal ecosystem thousands of kilometers away remain poorly understood. Here we tracked the chain ecological effects of an extreme rainfall event in North China from terrestrial rivers to coastal aquaculture area of the eastern Shandong Peninsula. Our data suggest the autumn flood resulted from extreme rainfall event leads to abnormally low turbidity in the North Shandong Coastal Currents and coastal red tide blooms by introducing anomalous freshwater with an exceptionally high nitrogen-to-phosphorus ratio into the Bohai Sea. Lower salinity, stronger light conditions caused by limpid coastal currents, and phosphorus limitation resulting from red tide blooms account for huge kelp loss offshore of the eastern Shandong Peninsula. This study underscores the importance of considering multidisciplinary observation for risk management of unexpected extreme weather events.

Far-field effects of the Nile damming on the silica cycle in the Southeastern Mediterranean Sea

Silica plays a key role in the growth of silicifying primary producers (e.g., diatoms) and hence the ocean carbon pump. The Mediterranean Sea's eastern Levantine Basin (ELB) is a low silica (and low N and P) ultra-oligotrophic basin. Before 1965, Nile autumn floods were a major source of dissolved silica (DSi) and other nutrients to primary producers of the ELB continental shelf, also known as the Nilotic cell. The construction of the Aswan High Dam (AHD) in the mid-1960s, blocked these floods, drastically diminishing the autumn-diatom blooms offshore the Nile delta. However, the far-reaching and long-lasting effects of the Nile damming on the Si cycle in the ELB remain unclear. Here, we studied the changes in DSi in the surface water offshore Israel and the distribution of biogenic silica in deep-sea short sediment cores, collected hundreds of kilometers from the Nile outlet, at depths range of 1100–1900 m, offshore the ELB Israeli coast. We show post dam reduction and termination in flood related seasonality of DSi and a concurrent decrease (of up to 79 %) in biogenic silica (BSi) accumulation rates in surficial sediments relative to underlying sediments. These changes reflect the effects of Si (dissolved and particulate) retention by the AHD on diatoms production, export and burial in the ELB. This far-field effect was demonstrated in deep-sea areas subjected to intense lateral transport of resuspended sediments from the shelf via intermediate nepheloid layers and to coastal water intrusions, along the path of the pre-dam, flood plumes. Our core records show that the AHD worsened nutrient-diminished, exceptionally unfavorable conditions for diatoms that persisted in the deep ELB at least during the last four millennia.

Refined analysis of flood-regional composition under changing environment in the middle reach of Hanjiang River

To investigate the flood-regional composition under changing environmental conditions in the middle reach of Hanjiang River (MHR), a data-driven hydrological simulation model and its related quantitative methods were developed. The flood-regional composition of Huangzhuang(HZ) in the MHR was quantitatively analyzed, and the influence of environmental changes on river flood routing was discussed. The primary research findings are as follows: ① A hydrological simulation model based on support vector regression machine (SVRM) is constructed to simulate the daily average flow process of HZ from 1965 to 2021. The Nash-Sutcliffe Efficiency (NSE) coefficient achieved values above 0.95, and the overall relative error (RE) was within ± 1 %, indicating excellent simulation performance. ② A quantitative analysis method has been proposed to identify the composition of flood areas. The results indicate that the upper reach of Hanjiang River (UHR) is the primary contributor to floods in the MHR, accounting for 60.62 % to 78.05 % of the total. The Tangbai River (TR) contributed between 14.1 % and 27.4 %, whereas the Nan River had a smaller contribution of only 6.83 % to 8.85 %. ③ Trend analysis indicates that the proportion of floods originating from the UHR increases in the summer flood season and decreases in the autumn flood season, while those changes of TR and Nanhe River (NR) are coincidental, especially in the autumn flood season, the proportion of floods in the TR increases significantly. The impact of floods from the UHR and TR cannot be ignored when implementing flood control measures. ④ A comprehensive analysis method has been proposed to quantify the integrated impacts of environmental changes. The results show that environmental changes had a relatively minor impact on flood routing and its flood-regional composition. However, they did affect the flood propagation process, resulting in earlier occurrences in peak flow, increased in peak discharge, and rapid rise and fall of floodwaters for floods exceeding 12,000 m3/s. These research findings provide strong foundational support for designing flood-regional, as well as flood control and disaster reduction systems in the MHR.

Philosophical Insights into the ‘great’ of Great River Culture through Chuang-tzu’s ‘Autumn Floods’

The Great River Culture, deeply embedded in the fabric of Chinese history, symbolizes the enduring legacy of the Yellow River and its influence on the cultural and spiritual development of the Chinese nation. Understanding the concept of ‘great’ within this cultural context is vital for appreciating its profound impact. In Chuang-tzu’s ‘Autumn Floods,’ the exploration of the relative nature of ‘small’ and ‘great’ provides an invaluable perspective for this understanding. This paper uses the method of literature analysis to delve into the philosophical content expressed by Chuang-tzu in the seven questions and answers between the Deity of the Yellow River and the Deity of the Northern Sea. Chuang-tzu elucidates that understanding the ‘small’ is necessary to discuss the great, the distinction between ‘small’ and ‘great’ is not constant, and the separation between the Dao and objects, along with the concept of reverting to the true essence. Hence, the ‘small’ and the ‘great’ are interdependent, with no fixed division between them. Discussing the ‘great’ only in the tangible and limited sense of ‘seeing things as objects’ is far from sufficient. The higher level of the intangible and infinite Dao represents the true essence of the concept of ‘great’ in river culture.

Temporal evolution of lake level fluctuations under flood conditions and impacts on the littoral ecosystems

Lake levels fluctuations are conditioned by seasonal variability, water resources management and climate change. Recent studies have shown that global warming potentially affects the risk of flooding and that the decisive factor for flood events is not temperature, but precipitation characteristics and hydrological conditions. Flood events have numerous impacts on social, economic and environmental aspects depending on how humans have altered lands, natural rivers and lake dynamics. Flood protection measures can cause conflicts with conservation measures and with ecosystem services because natural capital is not considered able to control floods and to contribute control floods and that it can contribute to human health and safety. In this paper we analysed the flood events in Lake Maggiore for return time periods of 3 – 5 – 10 – 25 – 50 – 100 – 250 – 500 years, considering the flood frequency in the last ten years using 1868-2021 as a reference period. We discussed the probability distribution of flood peaks, the correlation and linear regression between the lake level fluctuations and macroinvertebrates occurrence. We also presented lake coasts flood hazard mapping. The probability distribution that better describes the annual peak level is the Gumbel function, while for spring and autumn flood events the better distribution is the Log-Pearson type III. One of the historical flood events in terms of magnitude was in 2000, characterized by a return time of about 50 years. The last flood event in 2020, was characterized by a return period of about 10 years. Considering the seasonal frequency of flood, the autumn magnitude was higher than the spring one, and the differences between seasonal flood events progressively increased. The results suggested a high probability of a flood event every three years and also a forecast of a flood of about 197 m asl (3.14 m above the average lake level) every 10 years. Raising the lake level will affect the reed bed area from 193 m asl, and it will be more effective at 194.5 m (up to a 10% reduction). During flood events, the whole reed bed area is submerged. As regard macroinvertebrates composition and abundance, the first results show significant negative relationships between all sampling stations altogether vs the abundance of Cladotanytarsus sp. (Chironominae) and nearly significant positive relationships between water levels at Magadino vs Pscectrocladius sordidellus (Orthocladiinae) abundances. These few results are perhaps due to the current limited data availability.

Using mechanistic insights to predict the climate‐induced expansion of a key aquatic predator

AbstractAmeliorating the impacts of climate change on communities requires understanding the mechanisms of change and applying them to predict future responses. One way to prioritize efforts is to identify biotic multipliers, which are species that are sensitive to climate change and disproportionately alter communities. We first evaluate the mechanisms underlying the occupancy dynamics of marbled salamanders, a key predator in temporary ponds in the eastern United States We use long‐term data to evaluate four mechanistic hypotheses proposed to explain occupancy patterns, including autumn flooding, overwintering predation, freezing, and winterkill from oxygen depletion. Results suggest that winterkill and fall flooding best explain marbled salamander occupancy patterns. A field introduction experiment supports the importance of winterkill via hypoxia rather than freezing in determining overwinter survival and rejects dispersal limitation as a mechanism preventing establishment. We build climate‐based correlative models that describe salamander occupancy across ponds and years at two latitudinally divergent sites, a southern and middle site, with and without field‐collected habitat characteristics. Correlative models with climate and habitat variation described occupancy patterns better than climate‐only models for each site, but poorly predicted occupancy patterns at the site not used for model development. We next built hybrid mechanistic metapopulation occupancy models that incorporated flooding and winterkill mechanisms. Although hybrid models did not describe observed site‐specific occupancy dynamics better than correlative models, they better predicted the other site's dynamics, revealing a performance trade‐off between model types. Under future climate scenarios, models predict an increased occupancy of marbled salamanders, especially at the middle site, and expansion at a northern site beyond the northern range boundary. Evidence for the climate sensitivity of marbled salamanders combined with their disproportionate ecological impacts suggests that they might act as biotic multipliers of climate change in temporary ponds. More generally, we predict that top aquatic vertebrate predators will expand into temperate‐boreal lakes as climate change reduces winterkill worldwide. Predaceous species with life histories sensitive to winter temperatures provide good candidates for identifying additional biotic multipliers. Building models that include biological mechanisms for key species such as biotic multipliers could better predict broad changes in communities and design effective conservation actions.

Study on the Impact of Future Climate Change on Extreme Meteorological and Hydrological Elements in the Upper Reaches of the Minjiang River

Global warming increases global average precipitation and evaporation, causing extreme climate and hydrological events to occur frequently. Future changes in temperature, precipitation, and runoff from 2021 to 2050 in the upper reaches of the Minjiang River were analyzed using a distributed hydrological model, the SWAT (Soil and Water Assessment Tool), under a future climate scenario. Simultaneously, future variation characteristics of extreme climate hydrological elements in the upper reaches of the Minjiang River were analyzed using extreme climate and runoff indicators. The research shows that the frequency and intensity of the extreme temperature warming index will increase, while those of the extreme temperature cooling index will increase and then weaken in the upper reaches of the Minjiang River under a future climate scenario. The duration of precipitation, the intensity of continuous heavy precipitation, and the frequency of heavy precipitation will increase, whereas the intensity of short-term heavy precipitation and the frequency of heavy precipitation will decrease. However, spatial distribution of flood in the upper reaches is different, and thus flood risk in the upstream source area will still tend to increase. Particular attention should be given to the increase in autumn flood risk in the upper reaches of the Minjiang River.

Pre- and postprocessing flood forecasts using Bayesian model averaging

Abstract In this study, pre- and postprocessing of hydrological ensemble forecasts are evaluated with a special focus on floods for 119 Norwegian catchments. Two years of ECMWF ensemble forecasts of temperature and precipitation with a lead time of up to 9 days were used to force the operational hydrological HBV model to establish streamflow forecasts. A Bayesian model averaging processing approach was applied to preprocess temperature and precipitation forecasts and for postprocessing streamflow forecasts. Ensemble streamflow forecasts were generated for eight schemes based on combinations of raw, preprocessed, and postprocessed forecasts. Two datasets were used to evaluate the forecasts: (i) all streamflow forecasts and (ii) forecasts for flood events with streamflow above mean annual flood. Evaluations based on all streamflow data showed that postprocessing improved the forecasts only up to a lead time of 2–3 days, whereas preprocessing temperature and precipitation improved the forecasts for 50–90% of the catchments beyond 3 days' lead time. We found large differences in the ability to issue warnings between spring and autumn floods. Spring floods had predictability for up to 9 days for many events and catchments, whereas the ability to predict autumn floods beyond 3 days was marginal.

Comprehensive Evaluation of Surface Water Quality in the Flood Period of the Yellow River by Various Methods and Theories

Field monitoring of water quality during the autumn flood season in the middle and lower reaches of the Yellow River in 2021 was carried out. During this period, a host of methods, including the single-factor evaluation method, index evaluation method, and fuzzy mathematics method, were utilized to evaluate the water quality status. The relevant findings indicate that the water quality of the mainstream and tributaries in the middle and lower reaches of the Yellow River in the autumn flood season is excellent, which meets the water function zoning and water quality goals. In particular, the single-factor evaluation method emphasizes the use of the single index with the most serious pollution to represent the comprehensive water quality category, whereas the fuzzy mathematics method uses the multi-factor contribution rate to calculate the membership degree of water quality. Therefore, it is superior to the single-factor evaluation method in determining the water quality of the water functional zones within the evaluation scope. Meanwhile, the Nemerow index of the water quality of the tributaries of Yiluo River and Qinhe River at the section entering the Yellow River is lower than that of the mainstream, indicating that the water quality of tributaries is better than that of the mainstream during the monitoring period. Overall, the results of this research are conducive to the objective evaluation of the water quality of the Yellow River during the autumn flood season, thus providing more scientific technical support for the ecological conservation and restoration of the Yellow River basin.

Divergent runoff impacts of permafrost and seasonally frozen ground at a large river basin of Tibetan Plateau during 1960–2019

Since the 20th century, due to global warming, permafrost areas have undergone significant changes. The degradation of permafrost has complicated water cycle processes. Taking the upper Yellow River basin (UYRB) as a demonstration, this study discusses the long-term (1960–2019) changes in frozen ground and their hydrological effects with a cryosphere-hydrology model, in particular a permafrost version of the water and energy budget-based distributed hydrological model. The permafrost at the UYRB, with thickening active layer and lengthening thawing duration, has degraded by 10.8%. The seasonally frozen ground has a more pronounced intra-annual regulation that replenishes surface runoff in the warm season, while the degradation of permafrost leads to a runoff increase. The occurrence of extreme events at the UYRB has gradually decreased with the degradation of frozen ground, but spring droughts and autumn floods become more serious. The results may help better understand the hydrological impacts of permafrost degradation in the Tibetan Plateau.

River flooding on the French Mediterranean coast and its relation to climate and land use change over the past two millennia

River flooding triggered by extreme rainfall events is a major natural hazard that frequently causes fatalities and damages in southeastern France. A 2000-year record of flooding from the Hérault River basin was reconstructed using magnetic susceptibility data from lagoon deposits, supported by documentary databases of floods in coastal river basins from Languedoc over the last centuries. Flooding was particularly important between 800 and 1350 cal CE, i.e. during the warm climatic conditions of the Medieval Climate Anomaly. Moreover, several periods of increased flooding occurred in the 2nd, 6th-7th, 16th, 18th and 20th centuries. Increased flooding was significantly correlated with higher air temperature in the northwestern Mediterranean and with higher sea surface temperature in the Gulf of Lions. The analysis of relationships between river flooding and atmospheric conditions shows that autumn flood events in Languedoc were generally more frequent during the positive phase of the East Atlantic pattern, which is associated with southerly to southeasterly winds in the Gulf of Lions. Besides, increased flooding could also have been controlled by forest decline and human activities after 500 cal CE. Between 1400 and 1800 cal CE, palaeobotanical data show an intensification of land use characterized by an expansion of grasslands and cultivated areas in the coastal lowlands east of the Hérault River. Forest clearings and the development of agriculture seem to have led to a relative increase in river flooding, especially in the late Middle Ages and early modern period.

Investigating hydrological model versatility to simulate extreme flood events

We adapted a semi-distributed hydrological model (GRSD) to improve its versatility to simulate flood events occurring under different conditions, especially flash-floods after dry summer periods in the Mediterranean region. The adaptation introduces a dependency on rainfall intensity in the production function. The evaluation over 2008-2018 in the Aude catchment (France) showed that the new model structure does not deteriorate long-term model simulations obtained from the original model. The adapted model performed better than or equal to the original model in terms of differences in the timing of peak discharges, regardless of the season of the year when the flood occurs. The most important improvement was observed in the simulation of the magnitude of the flood peaks during autumn floods. A visualisation of model versatility allows detecting the time steps when the new model tends to behave more similarly or differently from the original model in terms of runoff production.

Seasonality of DOC Export From a Russian Subarctic Catchment Underlain by Discontinuous Permafrost, Highlighted by High‐Frequency Monitoring

AbstractIntense climate change and permafrost degradation impact northern watersheds and ultimately organic carbon transfer from terrestrial to aquatic ecosystems. We investigated the contemporary dissolved organic carbon (DOC) dynamics in a northern catchment underlain by discontinuous permafrost (Graviyka River, northern Siberia), where historical meteorological and hydrological data are available since 1936. Mean annual air temperature (MAAT), in contrast to precipitation and discharge was found to show a significant increasing trend since 1950. Using in situ sensing of fluorescent dissolved organic matter (fDOM), we estimated DOC concentrations at a high temporal frequency (1h) during 3 years (2015–2018), and calculated annual specific fluxes of 5.2–5.5 g C m2 yr−1. High DOC concentrations (above 10 mg L−1) are sustained all year, exhibiting nearly chemostatic behavior. Nevertheless, the high‐frequency survey of DOC and other water parameters revealed the seasonality of DOC origin and pathways in the watershed. The spring freshet dominates the annual export (up to 80%), but summer and autumn floods can also contribute up to 9% and 8% respectively. The high‐frequency sampling was able to capture the specific dynamic of DOC concentration during spring flood (DOC peak preceding discharge, dilution during the spring freshet) and summer and autumn floods (contribution of DOC‐rich, low conductivity water). These observations suggest a significant contribution of organic‐rich water originating in peatlands, potentially from degrading palsas. The study demonstrates both that high‐frequency sampling is essential to capture key events for DOC export, and that more long‐term monitoring is urgently needed in these rapidly evolving watersheds.

Geo-ecological aspects of water level extremums’ formation in the Don river waterways

The Don river basin has high population density, robust economy, but suffers from lack of water supply in low water level periods and seasons. This fact prompts researchers to study various aspects of the water resource dynamics. The analysis of the water flow volumes is demonstrating the decrease of the maximum spring flood water flows, the increase in the low level season water volumes, the leveling of the water flow volumes throughout the year and lower variance of the yearly water resource fluctuations. The duration of the spring floods and the summer-fall low water periods is increasing, but the flood maximums occur later (by 15-20 days), and the summer-fall low water periods start 15-25 days earlier compared to the previous century. The snow-related spring floods show anomalous patterns in terms of time of onset, duration, and height and shape of the flood wave. Autumn floods are episodic. The small rivers are showing signs of degradation, some of them are disappearing altogether. This is one of the reasons of the water resources depletion and the shift towards the earlier occurrence of the yearly low water level extremums. The low water flows and volumes of the current century pose risks for resource utilization.

Short-Term Impact of Tillage on Soil and the Hydrological Response within a Fig (Ficus Carica) Orchard in Croatia

Tillage is well known to have impacts on soil properties and hydrological responses. This work aims to study the short-term impacts of tillage (0–3 months) on soil and hydrological responses in fig orchards located in Croatia. Understanding the soil hydrological response in the study area is crucial for soil management due to frequent autumn floods. The hydrological response was investigated using rainfall simulation experiments (58 mm h−1, for 30 min, over 0.785 m2 plots). The results show that the bulk density was significantly higher 3 months after tillage than at 0 and 1 months. The water holding capacity and amount of soil organic matter decreased with time. The water runoff and phosphorous loss (P loss) increased over time. The sediment concentration (SC) was significantly higher 3 months after tillage than in the previous monitoring periods, while sediment loss (SL) and carbon loss (C loss) were significantly lower 0 months after tillage than 3 months after tillage. Overall, there was an increase in soil erodibility with time (high SC, SL, C loss, and P loss), attributed to the precipitation patterns that increase the soil water content and therefore the hydrological response. Therefore, sustainable agricultural practices are needed to avoid sediment translocation and to mitigate floods and land degradation.

Analysis of water level variations in the Huangzhuang reach (Hanjiang River, China) during recent years

Abstract. The 2017 Hanjiang autumn flood appeared to have higher surface water levels at the same discharge rate than previously at the Huangzhuang gauging station. It is seriously impacted the flood control. This paper analyses the 2000–2017 data from the Huangzhuang reach in the Hanjiang River, including surface water levels, the surface water fall, erosion-deposition variation and the engineering activities. A comparison of the 2016–2017 data with the 2000–2015 data in the Huangzhuang reach, revealed that the surface water levels were about 1.47 and 0.13 m higher in the high and intermediate discharge ranges, respectively. In the low discharge range, the 2016–2017 and 2010–2015 surface water levels were similar. However, a comparison of the 2016–2017 with the 2000–2009 data in the low discharge range, shows that the surface water levels were 0.28–0.4 m lower. The surface water fall in the Zhuandouwan–Huangzhuang's reach decreased in 2016–2017 for discharges above 5000 m3 s−1, whereas in the Huangzhuang–Datong reach the opposite was found. For other time periods and discharge ranges the fall decreased. In the Datong-Shayang reach the fall reduced in 2014–2015 relative to other periods in 2000–2017 in the discharge range above 5000 m3 s−1. The erosion-silting analysis for the Huangzhuang reach showed scouring of local river deposits due to bridge engineering. However, near the bridge the substantial silting was found. The collated surface water level and scouring-silting data suggest that reduced surface water levels during low discharge are mainly due to the overall river erosion. The increased surface levels in the high discharge range are due to local river siltation, especially because of the increased water resistance as response to bridge engineering.

The role of spatial and temporal model resolution in a flood event storyline approach in western Norway

We apply a physical climate storyline approach to an autumn flood event in the West Coast of Norway caused by an atmospheric river to demonstrate the value and challenges of higher spatial and temporal resolution in simulating flood impacts. We use a modelling chain whose outputs are familiar and used operationally, for example to issue flood warnings. With two different versions of a hydrological model, we show that (1) the higher spatial resolution between the global and regional climate model is necessary to realistically simulate the high spatial variability of precipitation in this mountainous region and (2) only with hourly data are we able to capture the fast flood-generating processes leading to the peak streamflow. The higher resolution regional atmospheric model captures the fact that with the passage of an atmospheric river, some valleys receive high amounts of precipitation and others not, while the coarser resolution global model shows uniform precipitation in the whole region. Translating the event into the future leads to similar results: while in some catchments, a future flood might be much larger than a present one, in others no event occurs as the atmospheric river simply does not hit that catchment. The use of an operational flood warning system for future events is expected to facilitate stakeholder engagement.