A gestão de recursos hídricos tornou-se cada vez mais complexa devido ao rápido crescimento sócio-econômico e as mudanças ambientais nas bacias hidrográficas nas últimas décadas. Modelos computacionais são importantes ferramentas de suporte na gestão de recursos hídricos e tomada de decisões devido a sua funcionalidade, provendo informações importantes sobre os principais processos físicos, químicos e biológicos, e permitindo melhorar o entendimento desses processos, os quais ocorrem em diferentes escalas espaciais e temporais. Na presente tese, o objetivo foi compreender o funcionamento hidrológico do sistema integrado bacia hidrográfica - lagoa, e os efeitos na hidrodinâmica do lago, utilizando como suporte o acoplamento da modelagem hidrológica - hidrodinâmica, e o uso de técnicas de sensoriamento remoto para o monitoramento de parâmetros de qualidade da água (e.g., clorofilaa, temperatura da superfície d’água e níveis da água). A área de estudo é a bacia hidrográfica da Lagoa Mirim, localizada no sul do Brasil, possuindo uma área total de 58.000 km2 (56% no Uruguai e o restante no Brasil). Foram propostos e testados modelos empíricos para estimativa de clorofila-a emumlago raso subtropical, baseados em imagens do sensor MODIS e técnicas estatísticas. Além disso, foi desenvolvido e avaliado o acoplamento da modelagem hidrológica-hidrodinâmica de grande escala e o sensoriamento remoto. O modelo hidrológico distribuído de grande escala MGBIPH acoplado com o modelo hidrodinâmico IPH-ECO foi utilizado para simular a bacia hidrográfica e os principais componentes hidrodinâmicos da Lagoa Mirim. O modelo mostrou bom desempenho quando comparado com observações de vazões, além de dados provenientes de sensoriamento remoto, através de altimetria espacial. As simulações mostraram importantes aspectos sobre a estrutura de fluxo, campos de velocidade e níveis d’água na lagoa, assim como a influência de grandes rios, forçantes externas como o vento (intensidade e direção) e o impacto do estressor antrópico (retiradas para irrigação) no sistema. As simulações permitiram avaliar aspectos relacionados com as variações espaciais e temporais (diurna, mensal, sazonal e inter-anual) da temperatura da superfície da água, a dinâmica dos fluxos de calor (sensível e latente) e os efeitos de eventos meteorológicos de pequena escala como frentes frias, os quais têm um impacto significativo sobre a temperatura superficial da água e os fluxos de calor na lagoa. Quanto aos modelos empíricos para estimativa de clorofila-a a partir do MODIS, os resultados mostram que um simples e eficiente modelo desenvolvido a partir de análise de regressão múltipla, apresentou ligeiras vantagens sobre os modelos de redes neurais artificiais, modelos multiplicativos não paramétricos e modelos empíricos (e.g., Appel, Kahru, FAI e O14a) usualmente utilizados na estimativa de Chl-a em ambientes aquáticos. Resultados também indicam que é inapropriado generalizar um único modelo desenvolvido a partir do conjunto total de dados, para estimar concentrações de Chl-a na lagoa, o que corrobora a heterogeneidade espacial na distribuição de Chl-a e as diferenças entre regiões (litoral e pelágica). A modelagem hidrológica-hidrodinâmica de grande escala apoiada por informação de sensoriamento remoto, mostrou ser uma abordagem promissora para o entendimento da estrutura e funcionamento de lagoas rasas de grande porte e longo prazo, úteis para a gestão integrada dos recursos hídricos. / The last decade, the water resource management is being complex due to the rapid socioeconomic development and environmental changes in river basins. Computations models are important support tools in water resource management and make decision providing important information and allowing a better comprehension of the physical, chemical and biologic processes, which occur in di erent temporal/spatial scales. In this thesis, the objective was to understand the hydrological functioning of the integrated basin- lake system and its e ects on hydrodynamics, using hydrodynamic - hydrodynamic modeling and water quality monitoring (e.g., chlorophyll-a, water surface temperature and water levels) from remote sensing techniques. The study area is the Lake Mirim basin, located between Brazil and Uruguay (basin total area 58.000 km2). Empirical models were proposed and tested to chlorophyll-a estimation in a shallow subtropical lake, based on MODIS imagery and statistics techniques. In addition, we developed and assessed the coupling of large scale hydrological/hydrodynamic modeling and remote sensing techniques. The large-scale distributed hydrological model MGB-IPH coupled with the hydrodynamic model IPHECO were used to simulate the river basin and the hydrodynamic components of the Lake Mirim. The coupled model showed good performance when compared to in-situ measurements and satellite altimetry data. The simulations showed important aspects relate to flow structure, velocity fields and lake water levels, as well as the influence of large rivers, external forcing as such the wind (intensity and direction), and the impact of anthropogenic stressors (irrigation withdrawals) in the system. The simulations allowed assessing the spatial and temporal variations (diurnal, monthly, seasonal and inter-annual) in the water surface temperature, heat fluxes dynamics (sensible and latent) and the e ects of short time-scale events, as such cold fronts passages over the lake, which cause strong impacts on the water surface temperature and heat fluxes in the lake. Regarding the empirical models developed to chlorophyll-a estimation from MODIS imagery, the results showed that a simple and e cient model developed from multiple regression analysis, performed best in comparison with artificial neural network models, non-parametric multiplicative models, and empirical models (e.g., Appel, Kahru, FAI and O14a) common used in the Chl-a estimation in aquatics environments. Results also indicated that is inappropriate to generalize a single model developed from the total datasets to estimates Chl-a in the lake, which corroborates the spatial heterogeneity (Chl-a distribution) and the di erences among regions (littoral and pelagic). The synergy between large-scale hydrological-hydrodynamic modeling, in situ measurements and remote sensing techniques provided a promising approach to improve the comprehension of the structure and ecosystem functioning of large shallow lakes in long-term time scale, useful to water resources management.

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Die vorliegende Arbeit befasst sich mit der Bestimmung des erforderlichen Deckwerkssteindurchmessers für eine Böschung an einer deutschen Binnenwasserstraße, welche unter der Belastung des Bugstrahlrudereinsatzes eines böschungsnah fahrenden Schiffes steht. Hierbei wird ausschließlich der Betrachtungsfall einer losen Steinschüttung (bestehend aus den Wasserbausteinen der geläufigen Größen- bzw. Gewichtsklassen) geschildert. Für die Bestimmung der Belastung des beschriebenen Bugstrahlrudereinsatzes wird auf die dreidimensionale hydronumerische Modellierung (3D-HN-Modellierung) zurückgegriffen. Der wesentliche Fokus innerhalb der 3D-HN-Modellierung liegt auf der Ausarbeitung der vorherrschenden turbulenten Strukturen, welche sowohl dem turbulenten Grundcharakter des Propulsionsstrahls als auch der Strahlumlenkung durch die bestehende Querströmung zugeordnet werden. Diesbezüglich präsentiert die Arbeit geeignete Modellannahmen (z. B. für die Berücksichtigung der Schiffsgeschwindigkeit), Randbedingungen (z. B. für den Propeller des Bugstrahlruders) sowie grundlegende Bedürfnisse an die Diskretisierung des Modellgebietes (z. B. aufgrund der Grenzschicht-Theorie von ebenen Wänden). Als Grundlage für die beschriebene Untersuchungsabsicht wird in einem ersten Schritt ein Überblick zur bestehenden Literatur bzw. zu den bestehenden und angewandten Ansätzen der Deckwerksbemessung infolge der Belastung eines Propulsionsstrahls bereitgestellt. Weiterhin müssen Erfahrungen zur Wirkungsweise einer Querströmung auf die Strahlausbreitung gesammelt und eingebunden werden. Aufgrund der böschungsnahen Fahrt des Schiffes steht dem umgelenkten Propulsionsstrahl ein zusätzlich beengter Ausbreitungs-raum zur Verfügung, welcher ebenfalls in die Betrachtungen einfließt. Auf Grundlage der beschriebenen Rahmenbedingungen wird die Wahl eines geeigneten Modellierungsansatzes innerhalb der 3D-HN-Modellierung vorgestellt. Damit die vorhandenen turbulenten Strukturen hinsichtlich ihrer Wirkungsweise an der Böschung erfasst werden können, bindet die vor-liegende Arbeit eine von Söhngen (2014) aufgestellte Auswertemethodik der bemessungsrelevanten, böschungsnahen Belastungsgrößen ein. Hierbei wird verstärkt auf die Rolle des Belastungsbetrags, der Belastungsorientierung sowie der Belastungsdauer eingegangen. Entsprechend der geschilderten komplexen Strömungssituation müssen geeignete Versuchsparameter definiert werden, welche in der Lage sind, potenzielle Gesetzmäßigkeiten der Strahlausbreitung und der daraus resultierenden Böschungsbelastung aufzuzeigen. Im Rahmen der vorliegenden Arbeit stehen die Einflüsse der Schiffsgeschwindigkeit, der Bugstrahlruderleistung sowie des Böschungsabstandes im Vordergrund, wohingegen weitere Einflussgrößen (wie z. B. die Böschungsneigung) unverändert bleiben. Im Anschluss an die Generierung der zeitlichen Belastungsverläufe an der Böschung beschreibt die vorliegende Arbeit ein Vorgehen zur Entkopplung der 3D-HN-Modellierung von der Mobilisierung eines Deckwerkssteins. Hierfür dienten Modellsteine aus physikalischen Modellversuchen der Bundesanstalt für Wasserbau als Datengrundlage für die Durchführung einer Computertomographie eines kompletten Modelldeckwerkes. Die daraus gewonnenen Einzelsteingeometrien werden hinsichtlich ihrer Ergebnisqualität interpretiert und abschließend mit den ermittelten Belastungsverläufen der 3D-HN-Modellierung innerhalb einer Festkörperbewegung vereinigt.:Symbolverzeichnis Abkürzungsverzeichnis Abbildungsverzeichnis Tabellenverzeichnis 1 Einführung und Motivation 1.1 Einleitung 1.2 Abgrenzung und Zielstellung dieser Arbeit 1.3 Methodisches Vorgehen 1.4 Gliederung der Arbeit 2 Theoretische Grundlagen 2.1 Konstruktionsarten von Bugstrahlruderanlagen 2.2 Propellerstrahltheorien 2.3 Vereinfachte Strahltheorie 2.4 Strahlausbreitung 2.4.1 Freie Strahlturbulenz 2.4.2 Propellerstrahl des Bugstrahlruders 2.4.3 Flüssigkeitsstrahlen in einer Querströmung 2.5 Erosionspotenzial des Propellerstrahls 2.5.1 Bewegungsbeginn von Gesteinspartikeln 2.5.2 Einfluss turbulenter Schwankungen 2.5.3 Deckwerksbemessung 2.6 Zusammenfassung 3 Numerische Modellierung turbulenter Fließprozesse 3.1 Grundlagen der 3D-HN-Modellierung 3.1.1 Erhaltungsgleichungen 3.1.2 Diskretisierung 3.1.3 Modellierungsstrategien 3.2 Aufbau und Wirkung der Wandgrenzschicht 3.3 Detached Eddy Simulation 3.4 Modellierung der Strömung innerhalb der Bugstrahlruderanlage 3.4.1 Ansatz einer ebenen Scheibe 3.4.2 Reale Propellergeometrie 3.5 Erfassung der böschungsnahen Strömungsverhältnisse 3.5.1 Abbildung der Böschung in der 3D-HN-Modellierung 3.5.2 Modellgebiet und Parametervariationen 3.5.3 Methodik zur Erfassung der Böschungsbelastung 3.5.4 Übertragung der Berechnungsergebnisse auf ein reales Schüttsteindeckwerk 3.6 Zusammenfassung 4 Deckwerksbelastung des Bugstrahlruders eines fahrenden Schiffes 4.1 Modellgebiet und Berechnungsdaten 4.2 Anströmung zum Bugstrahlruder 4.3 Strahlausbreitung 4.3.1 Strahlausbreitung innerhalb der Bugstrahlruderanlage 4.3.2 Strahlausbreitung außerhalb der Bugstrahlruderanlage 4.4 Böschungsbelastung 4.4.1 Belastungsschwerpunkt 4.4.2 Strahlangriffswinkel und modifizierter Strahlangriffsbeiwert 4.4.3 Deckwerkssteinbemessung 4.5 Zusammenfassung 5 Festkörperbewegung 5.1 Datengrundlage 5.2 Computertomographie 5.3 Aufbereitung der Einzelsteingeometrien 5.4 Ergebniskontrolle 5.5 Übergang zur Festkörperbewegung 6 Fazit und Ausblick Literaturverzeichnis Anhang / The present thesis addresses the reckoning of the required embankment stone diameter at German federal inland waterways, in order to guarantee a sustainable embankment stability against the bowthruster jet of closely passing by vessels. In doing so, the exclusive case being examined is armourstones in bulk (common classes of coarse particles and mass). From a systematic point of view the three-dimensional hydrodynamic modeling approach is used to determine the incoming strains of the bowthruster jet. Within this approach one of the main emphases is to highlight the prevailing turbulent structures, which can be assigned to the fundamental turbulent character of the jet as well as towards the bending of the jet entering a crossflow. In this regard the thesis presents suitable model assumptions (e.g. the consideration of the vessel movement), boundary conditions (e.g. the turning propeller) and model area requirements (e.g. due to the boundary layer theory at walls). As a basis for the described research intention an overview of the existing literature on bowthruster jets as well as the currently used design approach for armourstones in bulk is given. Furthermore, knowledge of the jet bending mechanism due to a crossflow has to be provided and included. Additionally, the role of the limited space between the vessel and the embankment has to be pointed out, as it forces the jet propagation to modify greatly. In consequence of the mentioned framework conditions, a suitable modeling approach which is able to comprehend the broad manifestations of turbulence is chosen. In order to achieve knowledge about the strain mechanism of the bended bowthruster jet on the embankment, the present thesis includes an evaluation algorithm given by Söhngen (2014). Within the evaluation algorithm the importance of the strain magnitude, the strain orientation as well as the strain duration is emphasized. In accordance with the outlined complex flow situation appropriate research parameters have to be defined, which enable the detection of potential regularities within the bended jet propagation as well as within the resulting strains on the embankment. Therefore, the present thesis primarily deals with the speed of the vessel, the installed capacity of the bowthruster and the embankment distance of the vessel, whereas additional influence quantities (e.g. the slope angle of the embankment) remain constant. Following the generating process of the embankment strains, an approach which detaches the three-dimensional hydrodynamic modeling of the strains from the mobilization of an individual armourstone is introduced. The required model stones originated from experimental modeling approaches of the Federal Waterways Engineering and Research Institute and were processed in order to conduct a computer tomography of a complete embankment model. Subsequent to the computer tomography the isolated stone geometries were processed, leading towards a reunification with the embankment strains within a rigid body simulation approach.:Symbolverzeichnis Abkürzungsverzeichnis Abbildungsverzeichnis Tabellenverzeichnis 1 Einführung und Motivation 1.1 Einleitung 1.2 Abgrenzung und Zielstellung dieser Arbeit 1.3 Methodisches Vorgehen 1.4 Gliederung der Arbeit 2 Theoretische Grundlagen 2.1 Konstruktionsarten von Bugstrahlruderanlagen 2.2 Propellerstrahltheorien 2.3 Vereinfachte Strahltheorie 2.4 Strahlausbreitung 2.4.1 Freie Strahlturbulenz 2.4.2 Propellerstrahl des Bugstrahlruders 2.4.3 Flüssigkeitsstrahlen in einer Querströmung 2.5 Erosionspotenzial des Propellerstrahls 2.5.1 Bewegungsbeginn von Gesteinspartikeln 2.5.2 Einfluss turbulenter Schwankungen 2.5.3 Deckwerksbemessung 2.6 Zusammenfassung 3 Numerische Modellierung turbulenter Fließprozesse 3.1 Grundlagen der 3D-HN-Modellierung 3.1.1 Erhaltungsgleichungen 3.1.2 Diskretisierung 3.1.3 Modellierungsstrategien 3.2 Aufbau und Wirkung der Wandgrenzschicht 3.3 Detached Eddy Simulation 3.4 Modellierung der Strömung innerhalb der Bugstrahlruderanlage 3.4.1 Ansatz einer ebenen Scheibe 3.4.2 Reale Propellergeometrie 3.5 Erfassung der böschungsnahen Strömungsverhältnisse 3.5.1 Abbildung der Böschung in der 3D-HN-Modellierung 3.5.2 Modellgebiet und Parametervariationen 3.5.3 Methodik zur Erfassung der Böschungsbelastung 3.5.4 Übertragung der Berechnungsergebnisse auf ein reales Schüttsteindeckwerk 3.6 Zusammenfassung 4 Deckwerksbelastung des Bugstrahlruders eines fahrenden Schiffes 4.1 Modellgebiet und Berechnungsdaten 4.2 Anströmung zum Bugstrahlruder 4.3 Strahlausbreitung 4.3.1 Strahlausbreitung innerhalb der Bugstrahlruderanlage 4.3.2 Strahlausbreitung außerhalb der Bugstrahlruderanlage 4.4 Böschungsbelastung 4.4.1 Belastungsschwerpunkt 4.4.2 Strahlangriffswinkel und modifizierter Strahlangriffsbeiwert 4.4.3 Deckwerkssteinbemessung 4.5 Zusammenfassung 5 Festkörperbewegung 5.1 Datengrundlage 5.2 Computertomographie 5.3 Aufbereitung der Einzelsteingeometrien 5.4 Ergebniskontrolle 5.5 Übergang zur Festkörperbewegung 6 Fazit und Ausblick Literaturverzeichnis Anhang

<div>With increasing focus on large scale planning and allocation of resources for protection against future flood risk, it is necessary to analyze and improve the deficiencies in the conventional flood modeling approach through a better understanding of the interactions between river hydrodynamics and subsurface processes. Recent studies have shown that it is possible to improve the flood inundation modeling and mapping using physically-based integrated models that incorporate observable data through assimilation and simulate hydrologic fluxes using the fundamental laws of conservation of mass at multiple spatiotemporal scales. However, despite the significance of integrated modeling in hydrology, it has received relatively less attention within the context of flood hazard. The overall aim of this dissertation is to study the heterogeneity in complex physical processes that govern the watershed response during flooding and incorporate these effects in integrated models across large scales for improved flood risk estimation. Specifically, this dissertation addresses the following questions: (1) Can physical process incorporation using integrated models improve the characterization of antecedent conditions and increase the accuracy of the watershed response to flood events? (2) What factors need to be considered for characterizing scale-dependent physical processes in integrated models across large watersheds? (3) How can the computational efficiency and process representation be improved for modeling flood events at large scales? (4) Can the applicability of integrated models be improved for capturing the hydrodynamics of unprecedented flood events in complex urban systems?</div><div><br></div><div>To understand the combined effect of surface-subsurface hydrology and hydrodynamics on streamflow generation and subsequent inundation during floods, the first objective incorporates an integrated surface water-groundwater (SW-GW) modeling approach for simulating flood conditions. The results suggest that an integrated model provides a more realistic simulation of flood hydrodynamics for different antecedent soil conditions. Overall, the findings suggest that the current practice of simulating floods which assumes an impervious surface may not be providing realistic estimates of flood inundation, and that an integrated approach incorporating all the hydrologic and hydraulic processes in the river system must be adopted.</div><div><br></div><div>The second objective focuses on providing solutions to better characterize scale-dependent processes in integrated models by comparing two model structures across two spatial scales and analyzing the changes in flood responses. The results indicate that since the characteristic length scales of GW processes are larger than SW processes, the intrinsic scale (or resolution) of GW in integrated models should be coarser when compared to SW. The results also highlight the degradation of streamflow prediction using a single channel roughness when the stream length scales are increased. A distributed channel roughness variable along the stream length improves the modeled basin response. Further, the results highlight the ability of a dimensionless parameter 𝜂1, representing the ratio of the reach length in the study region to maximum length of the single stream draining at that point, for identifying which streams may require a distributed channel roughness.</div><div><br></div><div>The third objective presents a hybrid flood modeling approach that incorporates the advantages of both loosely-coupled (‘downward’) and integrated (‘upward’) modeling approaches by coupling empirically-based and physically-based approaches within a watershed. The computational efficiency and accuracy of the proposed hybrid modeling approach is tested across three watersheds in Indiana using multiple flood events and comparing the results with fully- integrated models. Overall, the hybrid modeling approach results in a performance comparable to a fully-integrated approach but at a much higher computational efficiency, while at the same time, providing objective-oriented flexibility to the modeler.</div><div><br></div><div>The fourth objective presents a physically-based but computationally-efficient approach for modeling unprecedented flood events at large scales in complex urban systems. The application of the proposed approach results in accurate simulation of large scale flood hydrodynamics which is shown using Hurricane Harvey as the test case. The results also suggest that the ability to control the mesh development using the proposed flexible model structure for incorporating important physical and hydraulic features is as important as integration of distributed hydrology and hydrodynamics.</div>

Intense but short-term cloudbursts may cause severe flooding in urban areas. Such short-term cloudbursts mostly are of convective character, where the rain intensity may vary considerably within relatively small areas. Using uniform design rains where maximum intensity is assumed over the whole catchment is common practice in Sweden, though. This risks overestimating the hydraulic responses, and hence lead to overdimensioning of stormwater systems. The objective of this study was to determine how the hydraulic response to cloudbursts is affected by the spatial variation of the rain in relation to the catchment size, aiming to enable improved cloudburst mapping in Sweden. Initially, the spatial variation of heavy rains in Sweden was investigated by studying radar data provided by SMHI. The distribution of rainfall accumulated over two hours from heavy raincells was investigated, based on the assumption that the intensity of convective raincells can be approximated as spatially Gaussian distributed. Based on the results, three Gaussian test rains, whose spatial variation was deemed a representative selection of the radar study, were created. In order to investigate how the hydraulic peak responses differed between the Gaussian test rains and uniform reference rains, both test and reference rains were modeled in MIKE21 Flow model. The modelling was performed on an idealised urban model fitted to Swedish urban conditions, consisting of four nested square catchments of different sizes. The investigated hydraulic peak responses were maximum outflow, proportion flooded area and average maximum water depth. In comparison with spatially varied Gaussian rains centered at the outlets, the uniform design rain with maximum rain volume overestimated the peak hydraulic response with 1-8%, independent of catchment size. Uniform design rains scaled with an area reduction factor (ARF), which is averaging the rainfall of the Gaussian rain over the catchment, instead underestimated the peak response, in comparison with the Gaussian rains. The underestimation of ARF-rains increased heavily with catchment size, from less than 5 % for a catchment area of 4 km2 to 13 - 69 % for a catchment area of 36 km2. The conclusion can be drawn that catchment size ceases to affect the hydraulic peak response when the time it takes for the whole catchment to contribute to the peak response exceeds the time it takes for the peak to be reached. How much the rain varies over the area which is able to contribute to the peak response during the rain event, can be assumed to decide how much a design rain without ARF overestimates the peak responses. If the catchment exceeds this size, an ARF-scaled rain will underestimate the peak responses. This underestimation is amplified with larger catchments. The strong pointiness of the CDS-hyetograph used in the study risks underestimating the differences in hydraulic peak responses between the test rains and a uniform rain without ARF, while the difference between test rains and uniform rains with ARF risks being overestimated. / Intensiva men kortvariga skyfall kan orsaka omfattande översvämningsproblematik i urbana områden. Trots att sådana kortvariga skyfall oftast är av konvektiv karaktär, där regnintensiteten kan variera avsevärt inom relativt små områden, används idag uniforma designregn där maxintensitet antas över hela avrinningsområdet. Detta riskerar att leda till en överskattning av hydrauliska responser, och följaktligen överdimensionering av dagvattensystem. Denna studie syftar till att utreda hur den hydrauliska responsen av skyfall påverkas av regnets spatiala variation, i relation till avrinningsområdets storlek. Ytterst handlar det om att möjliggöra förbättrad skyfallskartering i Sverige. Initialt undersöktes den spatiala variationen hos kraftiga regn i Sverige, genom en studie av radardata tillhandahållen av SMHI. Utbredningen av regnmängd ackumulerad över två timmar från kraftiga regnceller undersöktes utifrån antagandet att intensiteten hos konvektiva regnceller kan approximeras som spatialt gaussfördelad. Baserat på resultatet skapades tre gaussfördelade testregn vars spatiala variation ansågs utgöra ett representativt urval från radarstudien. För att undersöka hur de hydrauliska responserna skiljer sig åt mellan de gaussfördelade testregnen och uniforma referensregn, modellerades såväl test- som referensregn i MIKE 21 Flow model. Modelleringen utfördes på en idealiserad stadsmodell anpassad efter svenska urbana förhållanden, bestående av fyra nästlade kvadratiska avrinningsområden av olika storlekar. De hydrauliska responser som undersöktes var maximalt utflöde, maximal andel översvämmad yta samt medelvärdesbildat maximalvattendjup, alltså toppresponser. Jämfört med spatialt varierade gaussregn centrerade kring utloppen överskattade ett uniformt designregn med testregnens maximala volym de hydrauliska toppresponserna med 1-8 %, oberoende av avrinningsområdets storlek. Uniforma designregn skalade med area reduction factor (ARF), vilken medelvärdesbildar gaussregnets nederbörd över avrinningsområdet, underskattade istället toppresponsen jämfört med gaussregnen. ARF-regnets underskattning ökade kraftigt med avrinningsområdets storlek, från mindre än 5 % för ett avrinningsområde på 4 km2, till 13 - 69 % för ett avrinningsområde på 36 km2. Slutsatsen kan dras att avrinningsområdets storlek upphör att påverka den hydrauliska toppresponsen, då tiden det tar för hela avrinningsområdet att samverka till toppresponsen överstiger tiden till denna respons. Hur mycket regnet varierar över det område som under regnhändelsen hinner samverka till toppresponsen, kan antas avgöra hur mycket ett designregn utan ARF överskattar toppresponserna. Överstiger avrinningsområdet denna storlek kommer ett ARF-regn att underskatta toppresponserna, och underskattningen förstärks med ökande avrinningsområdesstorlek. Den kraftiga temporala toppigheten hos den CDS-hyetograf som användes i studien riskerar att underskatta skillnaderna i hydraulisk topprespons mellan testregnen och ett uniformt regn utan ARF, medan skillnaden mellan testregn och uniforma regn med ARF istället riskerar att överskattas.