@misc{KhoshBinGhomashBachmannCaviedesVoulliemeetal., author = {Khosh Bin Ghomash, Shahin and Bachmann, Daniel and Caviedes-Voulli{\`e}me, Daniel and Hinz, Christoph}, title = {Introducing a dynamic spatiotemporal rainfall generator for flood risk analysis}, series = {EGU General Assembly 2023, Vienna, Austria, 24-28 Apr 2023}, journal = {EGU General Assembly 2023, Vienna, Austria, 24-28 Apr 2023}, doi = {10.5194/egusphere-egu23-2599}, abstract = {Precipitation scenario analysis is a crucial step in flood risk assessment, in which storm events with different probabilities are defined and used as input for the hydrological/hydrodynamic calculations. Rainfall generators may serve as a basis for the precipitation analysis. With the increase in the use of high resolution spatially-explicit hydrological/hydrodynamic models in flood risk calculations, demand for synthetic gridded precipitation input is increasing. In this work, we present a dynamic spatiotemporal rainfall generator. The model is capable of generating catchment-scale rainfields containing moving storms, which enable physically-plausible and spatiotemporally coherent precipitation events. This is achieved by the tools event-based approach, where dynamic storms are identified as clusters of related data that occur at different locations in space and time, and are then used as basis for event regeneration. The implemented methodology, mainly inspired by Dierden et al. (2019), provides an improvement in the spatial coherence of precipitation extremes, which can in turn be beneficial in flood risk calculations. The model has been validated under different databases such as the radar-based RADALON dataset or spatially-interpolated historical raingauge timeseries of different catchments in Germany, which is also presented in this work. The validation indicates the models ability to adequately preserve observed storm statistics in the generated timeseries. The generator is developed as an extension to the state-of-the-science flood risk modelling tool ProMaIDes (Promaides 2023). The model also puts great focus on user accessibility with offering features such as an easy installation process, support for most operating systems, a user interface and an online user manual.}, language = {en} } @misc{KhoshBinGhomashBachmannCaviedesVoulliemeetal., author = {Khosh Bin Ghomash, Shahin and Bachmann, Daniel and Caviedes-Voulli{\`e}me, Daniel and Hinz, Christoph}, title = {Effects ofWithin-Storm Variability on Allochthonous Flash Flooding: A Synthetic Study}, series = {Water}, volume = {15}, journal = {Water}, number = {4}, issn = {2073-4441}, doi = {10.3390/w15040645}, abstract = {Rainfall is a spatiotemporally variated process and one of the key elements to accurately capture both catchment runoff response and floodplain extents. Flash floods are the result of intense rainfall, typically associated to highly variable rain in both space and time, such as convective storms. In this work, the extent within-storm variability affects runoff and flooding is explored. The Kan catchment (Tehran, Iran) is used as base topography for the simulations. The allochthonous nature of floods in the catchment and how they interact with the effects of storm variability are further investigated. For this, 300 synthetic rainfall signals with different hyetograph variabilities are generated and imposed on a 1D/2D hydrodynamic model. Additionally, a set of simulations with different levels of spatial variability are performed. The results suggest that temporal and spatial variability affect the runoff response in different degrees. Peak discharge and hydrograph shapes, as well as flooded areas, are affected. The effect of storm temporal variability is shown to be significantly higher than storm spatial variability and storm properties such as return period, duration, and volume. Further on the influence of storm spatiotemporal variability on stream discharge and flood response is seen to be strongly dependent on the location within the drainage network at which it is assessed.}, language = {en} } @misc{KhoshBinGhomashBachmannCaviedesVoulliemeetal., author = {Khosh Bin Ghomash, Shahin and Bachmann, Daniel and Caviedes-Voulli{\`e}me, Daniel and Hinz, Christoph}, title = {Impact of Rainfall Movement on Flash Flood Response: A Synthetic Study of a Semi-Arid Mountainous Catchment}, series = {Water}, volume = {14}, journal = {Water}, number = {12}, issn = {2073-4441}, doi = {10.3390/w14121844}, abstract = {Rainfall is a spatiotemporally varied process and key to accurately capturing catchment runoff and determining flood response. Flash flood response of a catchment can be strongly governed by a rainfall's spatiotemporal variability and is influenced by storm movement which drives a continuous spatiotemporal change throughout a rainfall event. In this work, the sensitivity of runoff and flooded areas to rainfall movement are assessed in the Kan catchment (Iran). The allochthonous nature of floods in the catchment and how they interact with the effects of rainfall movement are investigated. Fifty synthetic rain hyetographs are generated and traversed over the catchment under different velocities and directions and used to force a 1D/2D hydrodynamic model. The results suggest rainfall movement affects the runoff response in different degrees. Peak discharge, hydrograph shapes and flooded areas are affected. Storms with higher velocities result in higher peaks and faster onsets of runoff and consequently higher flooded areas in comparison to slower storms. The direction of the movement also plays a role. Storms moving along the average direction of the stream result in higher peaks and flooded areas. The relevance of storm direction is greater for slow moving storms. Additionally, the influence of rainfall movement is modulated by hyetograph structure, and the allochthonous behavior is greatly dependent on the location within the drainage network at which it is assessed.}, language = {en} } @misc{KhoshBinGhomashCaviedesVoulliemeHinz, author = {Khosh Bin Ghomash, Shahin and Caviedes-Voulli{\`e}me, Daniel and Hinz, Christoph}, title = {Effects of erosion-induced changes to topography on runoff dynamics}, series = {Journal of Hydrology}, volume = {573}, journal = {Journal of Hydrology}, issn = {0022-1694}, doi = {10.1016/j.jhydrol.2019.04.018}, pages = {811 -- 828}, abstract = {Runoff generation from rainfall events is a complex, spatial and temporally dependent process strongly governed, among other factors, by catchment surface topography. Although it is widely known that many catchments experience morphological evolution, it is often ignored in analysis for different reasons ranging from simplification to lack of data. However, young catchments and early landscapes (such as those which are affected by natural or anthropogenic disturbances) do exhibit topography changes which in turn affect catchment hydrodynamics, hydrology and in particular runoff. In this work, we study the runoff generation and hydrodynamics of the H{\"u}hnerwasser artificial catchment (Brandenburg, Germany) during a period of erosion-based topographical changes (2006-2010). Nine Digital Elevation Models from such period were used as topography over which physically-based simulations were performed. The results suggest that topographic evolution in this catchment mostly affects the onset of runoff, whereas peak discharges and receding hydrograph limbs are less affected. These differences in hydrological signatures can be explained through the changes in the spatial distribution of runoff hydrodynamics and their impact on surface runoff connectivity. Relatively small topographical differences produce changing ponding conditions and modify flowpaths which becomes evident only through inspection of the spatial distribution of hydrodynamic variables. Moreover, the study shows that in order for simulations to be able to capture such responses, appropriate computational mesh and topographical data resolution are critical, since connectivity itself can be greatly affected by low resolution data or representation.}, language = {en} } @misc{KhoshBinGhomashBachmannCaviedesVoulliemeetal., author = {Khosh Bin Ghomash, Shahin and Bachmann, Daniel and Caviedes-Voulli{\`e}me, Daniel and Hinz, Christoph}, title = {Storm movement effects on the flash flood response of the Kan catchment}, series = {EGU General Assembly 2022, Vienna, Austria, 23-27 May 2022}, journal = {EGU General Assembly 2022, Vienna, Austria, 23-27 May 2022}, doi = {10.5194/egusphere-egu22-2494}, abstract = {Rainfall is a complex, spatial and temporally variated process and one of the core inputs for hydrological and hydrodynamic modelling. Most rainfalls are known to be moving storms with varying directions and velocities. Storm movement is known to be an important influence on runoff generation, both affecting peak discharge and the shape of hydrographs. Therefore, exploring the extent rainfall dynamics affect runoff generation and consequently flooded areas, can be an asset in effective flood risk management. In this work, we study how storm movement (e.g. characterized by velocity and direction) can affect surface flow generation, water levels and flooded areas within a catchment. Moreover, the influence of rainfall temporal variability in correlation with storm movement is taken into account. This is achieved by means of numerical-based, spatially explicit surface flow simulations using the tool ProMaIDes (2021), a free software for risk-based evaluation of flood risk mitigation measures. The storm events are generated using a microcanonical random cascade model and further on trajected across the catchment area. The study area is the Kan river catchment located in the province of Tehran (Iran) with a total area of 836 km², which has experienced multiple flooding events in recent years. Due to its semi-arid climate, steep topography with narrow valleys, this area has high potential for flash flood occurrence as a result of high intensity precipitation. The results of this study show a range of possible magnitudes of influence of rainfall movement on the catchment´s runoff response. The resulting flood maps highlight the importance of rainfall velocity and most importantly the direction of the movement in the estimation of flood events as well as their likelihood in catchment area. Moreover, its shown that the magnitude of influence of storm velocity and direction on discharge strongly depends on the location within the river network which it is measured.}, language = {en} } @misc{KhoshBinGhomashCaviedesVoulliemeHinz, author = {Khosh Bin Ghomash, Shahin and Caviedes-Voulli{\`e}me, Daniel and Hinz, Christoph}, title = {Effects of topography and infiltration heterogeneity on surface runoff and connectivity in the Huehnerwasser catchment}, series = {European Geosciences Union, General Assembly 2019, Vienna, Austria, 7-12 April 2019}, journal = {European Geosciences Union, General Assembly 2019, Vienna, Austria, 7-12 April 2019}, address = {Katlenburg-Lindau}, abstract = {The Huehnerwasser catchment is a monitored, early-development constructed catchment within the Lower Lausatia post-mining landscape in Germany. From the initial bare catchment state, a sequence of landscape-forming processes occurred, including erosion-based topographic change and vegetation establishment, which are at the centre of this study. Erosion-based topographic change is strongly driven by surface runoff, while in turn itself also modifying runoff in the catchment. These topographic changes can have a significant impact on the hydrological response of a catchment, as they can affect flow paths, flow speeds and rainfall-runoff-infiltration partitioning, all of which manifest in different ways in runoff hydrographs in response to rainfall events. Vegetation establishment enhances local infiltration capacity, introducing infiltration heterogeneity, thus affecting the topography-controlled flowpaths as water infiltrates at vegetation patches. Critical-zone observatories and monitored early-development systems allow to document signatures of the evolution of catchments and to correlate certain behaviours to processes. However, readily and easily achievable runoff signatures often cannot provide a clear nor full description of process interactions, as the individual roles of processes are stacked together, and strongly shaped by the temporal distribution of rainfall, making it very difficult to disentangle the effects of each process, and making modelling a necessary approach to understand these interactions and their manifestations. All such processes occur at small spatial scales, and are difficult to observe or assess when experimentally studying catchment hydrology. Moreover, given that the complexity of processes contributing to morphological changes and the corresponding alteration of runoff signatures, single catchment experiments and even comprehensive monitoring programmes of whole catchments will neither allow to decipher all processes interactions nor will it allow to apply a statistically derived experimental. In this work, we study the effects that spatial distributions of surface topography and infiltration properties have on surface runoff and surface connectivity in response to single rainfall events, in the context of the Huehnerwasser catchment. We simulate rainfall/runoff processes by means of a physically-based, spatially explicit surface flow model, and assess the results in terms of hydrological signatures (hydrograph, hydrological balance), spatial distribution of the hydrodynamics of runoff, and surface flow connectivity. To do this, we use several DEMs of the H{\"u}hnerwasser catchment recorded during the erosion-based development of the surface (2006-2010), different hypothetical infiltration properties distributions, and a set of different singular rainfall events. The study allows to observe the individual effects that topographic properties and infiltration distributions have on the hydrograph signatures and connect cause-and-effect through an intermediate, conceptual property of the system: surface runoff connectivity, arguably an indicator of hydrological organisation of the runoff response. Moreover, by systematic analysis, the interactions between topography and infiltration can also be assessed in the hydrograph and explained through connectivity. The results show a range of possible magnitudes of influence of topography and infiltration on the runoff response, while highlighting that the onset of runoff and the rising limb of the hydrograph are mostly affected by these features and their interactions, and strongly related to surface runoff connectivity.}, language = {de} } @misc{KhoshBinGhomashCaviedesVoulliemeHinz, author = {Khosh Bin Ghomash, Shahin and Caviedes-Voulli{\`e}me, Daniel and Hinz, Christoph}, title = {Effects of topography and infiltration heterogeneity on surface runoff and connectivity in the H{\"u}hnerwasser catchment.}, series = {European Geosciences Union, General Assembly 2019, Vienna, Austria, 7-12 April 2019}, journal = {European Geosciences Union, General Assembly 2019, Vienna, Austria, 7-12 April 2019}, address = {Katlenburg-Lindau}, language = {en} }