Regionalization of an event based Nash cascade model for flood predictions in ungauged basins
01 Jan 2008-
TL;DR: In this paper, an event based hourly Nash cascade model was developed to derive the direct runoff hydrograph from rainfall time series, which was implemented on a semi-distributed scale.
Abstract: This study was aimed at developing a practical, robust and physically reasonable methodology for estimation of design flood under data scarce conditions. Due to lack of sufficient discharge data and inconstant hydrological conditions, application of discharge-frequency analysis or calibration of a hydrological model is not always viable. In such cases model parameters are obtained through regionalization procedure.
The main objective of this study was to derive a regionalization methodology for flood predictions in ungauged catchments, which is strictly based on physically reasonable transfer functions and adequately addresses the problem of parameter equifinality. A possibility of assessment of impact of land use changes on flood characteristics was also investigated during the study.
An event based hourly Nash cascade model was developed to derive the direct runoff hydrograph from rainfall time series. The model was implemented on a semi-distributed scale, i.e. the direct runoff hydrograph is estimated at sub-catchment scale, and then it is routed to the outlet of the catchment using the Muskingum routing procedure. The model uses three parameters, the runoff coefficient (RC), the number of reservoirs (N) and a reservoir constant (K). For ungauged catchments, the model parameters RC, N and K must be estimated through a regionalization procedure.
The study was conducted using 209 rainfall-runoff events from 41 mesoscale catchments in the south-west region of Germany. Among the 41 catchments, 22 were used for optimization of the regionalization methodology and 19 were used for its validation. Areal rainfall time series for the events were estimated through external drift kriging. Various event and catchment specific hydrological characteristics, describing event specific conditions were estimated for each of the events.
Four different approaches were employed to derive four different transfer functions for RC: a multiple linear transfer function (MLTF), an artificial neural network transfer function (ANNTF), a fuzzy logic transfer function (FLTF) and a logistic transfer function (LoTF). ANNTF, FLTF and LoTF exhibited a high goodness fit performance for the events in the regionalization as well validation set. In order to investigate whether the transfer functions are physically reasonable, validation for physical relationships was carried out by comparing the signs of derivatives of the functional relationships between the predictors and RC, as featured in the transfer functions, with the signs of derivatives of the physical relationships. The validation revealed that the response of ANNTF and FLTF to hydrological changes often conflicts with the response of the physical relationships. On the other hand, the response of LoTF was consistent with that of the physical relationships, which indicates that it is physically reasonable.
The Nash cascade parameters N and K exhibit strong inter-parameter relationship which can be represented by a power function with an exponent (α = -1.0) and a coefficient β. Therefore, regionalization of K and the coefficient β was carried out, where N can be estimated by using K and the inter-parameter function. The transfer functions were optimized by using mean Nash-Sutcliffe coefficient as an aggregated goodness fit measure for a set of gauged catchments.
During the optimization and the validation of the transfer functions, highly acceptable aggregated goodness fit performance was achieved, which indicates that the transfer functions are both reliable and efficient at transferring the model parameters to ungauged catchments. The validation of the transfer functions for physical relationships was carried out by comparing the change in the shape of modeled unit hydrograph, due to change in the hydrological characterisics, with the change anticipated from the a priori knowledge of runoff propagation processes.
The comparisons with the existing common practices, such as SCS curve number method and the Lutz procedure, revealed that for the study area under consideration, the regionalization methodology performs better than the existing practices. The regionalization methodology is built on physically reasonable relationships with event as well as catchment specific hydrological characteristics. Therefore, it is robust and suitable for both the temporal as well as the spatial transfer of the model parameters. The assessment of impact of land use changes on flood characteristics was carried out for three different land use scenarios in the catchment Tubingen. The attempt led to the conclusion that there is a reasonable chance of using such methodology for assessment of impact of land use changes.
Diese Untersuchung beschaftigte sich mit der Entwicklung einer praktischen, robusten und physisch begrundeten Methodologie zur Schatzung der Bemessungshochwasser und ihrer Eigenschaften in Regionen mit mangelhafter Datengrundlage. Allerdings ist, aus Mangel an ausreichenden Abflussdaten und nicht-stationaren hydrologischen Verhaltnissen, die Anwendung der die Abfluss-Frequenz Analyse oder Kalibrierung eines hydrologischen Modells nicht immer geeignet. In diesem Fall mussen, anstelle der Kalibrierung, die Modell-Parameter mit einem Regionalisierungsverfahren berechnen werden.
Das Hauptziel dieser Untersuchung war es, eine Regionalisierungsmethodologie zu entwickeln, die auf physisch begrundeten Transfer-Funktionen basiert und das Parameter-Identifizierungs- Problem adaquat berucksichtigt. Zusatzlich wurde untersucht, ob es moglich ist, die Auswirkungen von Landnutzanderungen auf die Hochwasser-eigenschaften zu bewerten.
Es wurde ein ereignisbasiertes Nash-Kaskade-Modell mit einstundiger Auflosung entwickelt, um den Hydrographen des Direktabflusses aus der Niederschlagszeitreihe abzuleiten. Das Modell wurde auf ein semi-flachendifferneziertes Modellgebiet angewendet, d.h. die Abflussganglinie wird fur Untereinzugsgebiet geschatzt, dann die Abflussganglinie an der Mundung des Einzugsgebiet mit Muskingum Routing-Verfahren weiterleitet. Das Modell verwendet drei Modellparameter, den Abfluss Koeffizienten (RC), die Zahl der Reservoire (N) und die Reservoir Konstante (K). Fur unbeobachteten Einzugsgebieten, mussen die Modellparameter RC, N und K durch ein Regionalisierungsverfahren geschatzt werden.
Die Untersuchung wurde mit 209 Niederschlag-Abfluss Ereignissen aus 41 Einzugsgebieten im Sud-Westen von Deutschland durchgefuhrt. Von den 41 Einzugsgebieten, wurden 22 zur Ableitung der Regionalisierungsmethodologie und 19 zur Validierung der Methodologie verwendet. Der Gebietsniederschlag fur die Ereignisse wurde durch Externe-Drift-Kriging abgeschatzt. Fur jedes Regenereignis wurden verschiedene sowohl ereignis-, als auch einzugsgebietsspezifische hydrologische Merkmale bestimmt.
Vier verschiedene Ansatze zur Ableitung vier verschiedener Transfer-Funktionen fur RC wurden verwendet: eine multiple lineare Transfer-Funktion (MLTF), eine neuronales Netzwerk Transfer-Funktion (ANNTF), eine Fuzzy-Logik Transfer-Funktion (FLTF) und eine logistische Transfer-Funktion (LoTF).
Bei der Regionalisierung und Validierung zeigten ANNTF, FLTF und LoTF hohe Anpassungsguten. Um zu untersuchen, ob die Transfer-Funktionen physikalisch sinnvoll sind, wurde eine Validierung des physikalischen Zusammenhangs durchgefuhrt. Die Vorzeichen der Ableitungen des funktionalen Zusammenhangs zwischen Predigtoren und RC in der jeweiligen Transfer-Funktion wurden mit den Vorzeichen verglichen, die sich aus dem Wissen uber den physikalischen Zusammenhang ergeben. Die Validierung zeigte auf, dass die Reaktion der ANNTF und FLTF auf hydrologische Veranderungen oft den physikalischen Beziehungen widerspricht. Auf der anderen Seite hat die Validierung von LoTF fur die physikalischen Beziehungen gezeigt, dass die Vorzeichen der Ableitungen der funktionalen Beziehungen den physikalischen Beziehungen, ubereinstimmen. Somit ist LoTF robust und physisch sinnvoll.
Die Nash-Kaskade Parameter N und K besitzen stark Beziehung mit einander und die mit einer interparametrischen Funktion formulieren kann. Die inter-parametrische Funktion kann durch eine Potenzfunktion mit einem Exponent α = -1,0) und einem Koeffizient (β) reprasentiert werden. Daher wurde eine Regionalisierung von K und β durchgefuhrt, wobei N mittels K und der interparametrischen Funktion geschatzt werden kann. Die Transfer-Funktionen wurden uber den gebietsgemittelten Nash-Sutcliffe Koeffizient (NS) optimiert, als ein aggregiertes Mas der Anpassungsgute fur ein Set an beobachteten Einzugsgebieten.
Die Anpassungsgute Leistung der abgeleitete Regionalisierungsmethodologie bei der Optimierung und der Validierung deutet darauf hin, dass die Methodologie hoch effizient ist zur Abschatzung des Hochwasser in den unbeobachteten Einzugsgebieten. Die Regionalisierungsmethodologie basiert auf physikalisch begrundeten Beziehungen zu Ereignis- und Einzugsgebietspezifischen hydrologischen Merkmalen.
Der Vergleich mit ublicherweise verwendeten Anwendungen, wie zum Beispiel der SCS-Curve-Number Methode und dem Lutz Verfahren, ergab, dass die Regionalisierungsmethodologie fur das Untersuchungsgebiet zu besseren Ergebnissen fuhrt als die ublichen Anwendungen. Diese Bewertung von Landnutzungsanderungen wurde fur drei verschiedene Landnutzungsszenarien im Einzugsgebiet Tubingen durchgefuhrt. Der Versuch fuhrte zu der Aussage, dass es moglich ist, die Methodologie zur Bewertung der Beeinflussung von Landnutzanderungen anzuwenden.
Citations
More filters
01 Jan 2010
TL;DR: In this paper, the authors developed an efficient, practical and robust methodology for parameter estimation (calibration) for a reliable hydrological modeling at gauged and ungauged basin.
Abstract: Hydrological modeling has become a widely accepted theoretical tool for water resources engineering and management. Rainfall-runoff models are used both for short and medium time management (for example flood forecasting) and long-time design purposes. However, the application of hydrological models is limited due to several reasons. One important limitation is imposed by the availability of data and parameter estimation. Discharges are only measured at a few selected river cross sections, leading to a small number of catchments for which the runoff calculated from the models might be verified. Further, the high spatial and temporal variability of the meteorological input (such as precipitation, temperature or wind) cannot fully be captured by the usually small number of meteorological stations. Radar measurement of precipitation can provide more detailed space time information on precipitation but unfortunately the reliability of the data is at present still low. Other influencing factors such as soil properties also vary considerably in space and even to some extent in time (for example macropores in soils). These problems among others make models which are based on physical principles only infeasible for many practical applications. Models which to some extent use analogous concepts can partly smoothen out the effects of variability and thus can often be successfully used for practical purposes. The limitation of these models lies in the fact that some of their parameters are not directly related to physically measurable quantities. Therefore those have to be estimated from observations using calibration techniques.
This research work was aimed at developing an efficient, practical and robust methodology for parameter estimation (calibration) for a reliable hydrological modeling at gauged and ungauged basin. The main focus of this research was to bring more insight into the process of parameter estimation techniques in hydrological modeling. The other objective of this research work was to develop a methodology that enables regional estimation of parameters of a conceptual continuous water balance model based on physical catchment descriptor, which includes the land use, soil type, stream network, elongation and topographic attributes of the catchment. It aims at improving the weakness inherent in the traditional two-step regionalization approach in estimating the relationship between the model parameters and the physical catchment descriptor. The specific objectives of the research were to answer some basic question as listed below:
- How can we estimate hydrologically reliable parameters for modeling?
- How do different objective functions map parameter space during calibration?
- Can we calibrate a hydrological model using carefully selected critical events?
- Can we improve prediction and model diagnosis by including dynamic variability in parameters?
- How can we extend hydrologically reliable parameters from gauged to ungauged basins?
In this research, several algorithms, for example, ROPE, SRWP, HOP, ICE, RDPE and SAV algorithm were developed to answer the basic questions mentioned above. These algorithms were very useful for the robust and reliable hydrological modeling in gauged and ungauged basins.
Die hydrologische Modellierung ist zu einem anerkannten theoretischen Hilfsmittel in der Wasserwirtschaft geworden. Niederschlagsabflussmodelle werden sowohl fur kurz und mittelfristige Fragestellungen (wie z.B. Hochwasservorhersage), als auch fur langfristige Planungszwecke eingesetzt. Allerdings ist der Einsatz von hydrologischen Modellen aus verschiedenen Grunden beschrankt. Eine wesentliche Einschrankung fur den Einsatz von hydrologischen Modellen ist die Datenverfugbarkeit und die Parameterabschatzung. Abflusse werden nur an einzelnen ausgewahlten Flussquerschnitten gemessen, weshalb es nur eine geringe Anzahl von Einzugsgebieten gibt, fur die der berechnete Abfluss nachgepruft werden kann. Des Weiteren kann die hohe raumliche und zeitliche Variabilitat der meteorologischen Eingangsdaten wie Niederschlag, Temperatur oder Wind nicht vollstandig von der in der Regel geringen Anzahl an Wetterstationen erfasst werden. Radarmessungen konnen eine detailliertere raumliche und zeitliche Auflosung des Niederschlags liefern, allerdings ist die Verlasslichkeit dieser Daten immer noch gering. Andere beeinflussende Faktoren, wie z.B. Bodeneigenschaften, variieren raumlich ebenfalls deutlich und in manchen Fallen sogar zeitlich (z.B. Makroporen im Boden). Durch diese und andere Probleme sind physikalisch-basierte Modelle fur viele praktische Anwendungen nicht verwendbar. Verschiedene Modelle, die auf teilweise gleichen Konzepten basieren, konnen die Einflusse der Variabilitat herausfiltern und somit oft erfolgreich fur praktische Aufgaben eingesetzt werden. Die Einschrankung bei solchen Modellen beruht darauf, dass einige ihrer Parameter nicht direkt mit physikalisch messbaren Grosen zusammenhangen. Deshalb mussen solche Parameter durch Beobachtungen mit Hilfe von Kalibrierungsmethoden abgeschatzt werden.
Das Ziel dieser Forschungsarbeit war die Entwicklung von effektiven, praktischen und stabilen Methoden der Parameterabschatzung, welche fur eine zuverlassige hydrologische Modellierung sowohl in beobachteten als auch in unbeobachteten Einzugsgebieten eingesetzt werden sollen.
Der Schwerpunkt wurde darauf gelegt, einen vertieften Einblick im Prozess der Parameterschatzung in der hydrologischen Modellierung zu bekommen.
Ein weiteres Ziel war die Entwicklung einer Methodik zur regionaler Parameterschatzung eines auf physikalischen Eigenschaften des Einzugsgebietes basierendes konzeptionelles kontinuierliches Wasserbilanzmodells. Unter den physikalischen Eigenschaften befinden sich Landnutzung, Bodentyp, Struktur und Lange des Flussnetzwerks sowie die Topographie des Einzugsgebietes.
Durch Schatzung der Beziehung zwischen den Modellparametern und den physikalischen Grosen im Einzugsgebiet zielt es die Methodik an, die im traditionell zweistufigen Regionalisierungsansatz angeborenen Schwachstellen zu mindern. Ferner sollten grundsatzliche Fragen beantwortet werden, wie z.B.:
- Wie konnen die fur das Modellieren hydrologisch zuverlassige Parameter abgeschatzt werden?
- Wie bilden unterschiedliche Zielfunktionen den Parameter-Raum wahrend der Kalibration ab?
- Kann ein hydrologisches Modell mit sorgfaltig ausgewahlte kritischen Ereignisse kalibriert werden?
- Konnen Vorhersage und Modelldiagnose durch Einschluss dynamischer Variabilitat in Parametern verbessert werden?
- Wie konnen hydrologisch zuverlassige Parameter von beobachtete auf unbeobachtete Einzugsgebiete ausgeweitet werden?
In dieser Forschungsarbeit wurden zur Beantwortung der obenerwahnten Fragen mehrere Algorithmen (z.B. ROPE, SRWP, HOP, ICE, RDPE und SAV) entwickelt. Diese haben sich fur eine robuste und zuverlassige hydrologische Modellierung sowohl in beobachteten als auch in unbeobachteten Einzugsgebieten als sehr nutzlich erwiesen.
62 citations
Cites background from "Regionalization of an event based N..."
...This is mainly due to the lack of very clear and sound understanding of physics behind rainfall-runoff process and in adequate representation of the available process knowledge (Patil, 2008)....
[...]
01 Jan 2009
TL;DR: In this article, the authors proposed a method for estimating the storage capacity of deep saline aquifers for a CCS project, which is a challenging task since usually few data are available and the prognosis of the complex processes occurring in a reservoir after CO2 injection is difficult.
Abstract: The concentration of greenhouse gases in the atmosphere has increased due to tremendous human fossil fuel consumption since the Industrial Revolution. This is most likely the cause for an observed global increase in the average temperature and for the changing climate. It is expected that further global warming will have drastic ecological and economic impacts.
No single technology will be sufficient to achieve the necessary emission reductions. Carbon dioxide capture and storage (CCS) is a promising technology which could make a substantial contribution. It is a process which captures CO2 from large local sources and then stores it away from the atmosphere. Storage capacity estimates for deep saline aquifers are most promising. The initial procedure for selecting a few aquifers for a CCS project is called site screening. Aquifers identified in site screening then have to prove their suitability in further investigations. Site screening is a challenging task, since usually few data are available and the prognosis of the complex processes occurring in a reservoir after CO2 injection is difficult.
This study aims at improving the insight into CO2 injection processes in geological formations to assist site screening. The criteria in site screening include the estimation of the storage capacity, which should be sufficient to store the long-term production of the CO2 source, and the long-term ability to store CO2 ,which is related to the efficiency of the project and risk arising due to possible CO2 leakages. At first, the statistical characteristics of storage sites in potential geological formations are calculated by analysis of a large database. The parameter ranges and distributions are used to define typical reservoirs and serve as a basis for generating random reservoir setups respecting statistical characteristics. The relation of forces occurring in reservoirs after CO2 injection is analysed by dimensional analysis. By the identification of dominant forces and processes, reservoirs with different parameter setups are compared with respect to their potential CO2 storage capacity and risk. A sophisticated concept for estimating the CO2 storage capacity of geological formations is developed. Detailed, time-dependent storage-capacity estimates are calculated in numerical experiments. The results are interpreted using the simultaneously calculated ratios of forces. The influence of individual reservoir parameters on storage capacity and risk is investigated in a sensitivity analysis. Finally, a risk analysis on potential
CO2 leakage through pre-existing wells is performed. In numerous numerical experiments, individual parameters are randomly sampled from the statistical parameter distributions and leakage is calculated. A risk surface is derived which represents the average risk for CO2 leakage through pre-existing wells for any site with unknown reservoir properties.
Aufgrund des enormen Verbrauchs an fossilen Brennstoffen in den letzten 160 Jahren, stieg die Konzentration der Treibhausgase in der Atmosphare stark an. Dieser Anstieg der Treibhausgaskonzentrationen ist mit groster Wahrscheinlichkeit die Ursache fur den weltweiten Temperaturanstieg und die beobachteten Klimaveranderungen. Man erwartet, dass ein weiterer Temperaturanstieg zu tiefgreifenden okologischen Veranderungen und okonomischen Belastungen fuhren wird.
Eine einzelne Technologie oder Masnahme wird die notige Verringerung der Treibhausgasemissionen nicht leisten konnen, deshalb muss gleichzeitig eine ganze Reihe an Masnahmen ergriffen werden. Zu diesen Masnahmen gehoren z.B. eine effizientere Energiegewinnung und -nutzung, der Ausbau der Nutzung regenerativer Energien, die erhohte Verwendung treibhausgasarmer Brennstoffe sowie die Abscheidung des CO2 im Abgasstrom von grosen CO2-Produzenten und die anschliesende Einlagerung in tiefe geologische Schichten oder der Tiefsee (CCS).
Der Fokus dieser Arbeit liegt auf der Abscheidung und Speicherung von CO2 in tiefen geologischen Schichten. Mit der vorliegenden Arbeit soll das Prozessverstandnis von CO2 Injektionen in geologische Formationen verbessert werden um die anfangliche Standortauswahl innerhalb einer Region zu unterstutzen. Diese Phase eines Projekts ist typischerweise durch einen Mangel an detaillierten Standortinformationen gekennzeichnet. Um eine Vorauswahl treffen zu konnen, muss dennoch die Speicherkapazitat einer Formation abgeschatzt werden. Auserdem muss die Eignung der Formation das CO2 uber lange Zeitraume sicher verwahren zu konnen nachgewiesen werden. Dieser Nachweis ist notig um den Projekterfolg sicherzustellen sowie eventuelle Risiken zu vermeiden. Die Untersuchung dieser Fragestellungen erfolgt in dieser Arbeit uber die statistische Analyse einer Datenbank relevanter Formationsparameter, sowie uber analytische und numerische Experimente.
53 citations
TL;DR: In this paper, the authors discussed how model coupling could help in reducing the model complexity and increasing model efficiency while the relevant processes are still taken into account while the coupling concepts are discussed.
51 citations
DOI•
01 Jan 2012
TL;DR: In this article, a multivariate fuzzy-logic model is proposed to simulate the quality of reproduction habitats for gravel-spawning fish using physical habitat modelling. But the model is not suitable for aquatic habitats.
Abstract: The complexity and dynamic nature of ecosystem processes impose high requirements on the approaches, methods and modelling techniques applied to support ecological assessments of rivers. Particularly the interactions of abiotic and biotic variables, the high spatial and temporal variability of parameters and processes and the interdisciplinary research field present a special challenge on the development of appropriate tools. Given the naturally dynamic creation, destruction and maintenance of habitat templates in rivers (habitat dynamics) the habitat can be regarded as a basic element of fluvial ecosystems. Accordingly, high demands are placed on aquatic habitat modelling techniques emphasizing the need for the improvement and further development of existing approaches.
The present study predominantly addresses three research fields encompassing the hydromorphology, the fluvial ecology and the hyporheic interstitial of rivers. All disciplines are involved by interacting processes defining the quality of reproduction habitats for gravel-spawning fish. This work is focused on implementing the hydromorphological and hyporheic variability in physical habitat modelling considering all variables that describe the habitat in their spatial and temporal variability to allow a dynamic representation of habitat suitability. The reproduction period of gravel-spawning fish works as an excellent indicator for interstitial habitats, as the life-stages during reproduction are characterised by high requirements on the habitat. Based on the abiotic description of the environment a multi-step habitat modelling framework is developed that addresses each life-stage during the reproduction by an appropriate selection of key habitat variables that are linked via a multivariate fuzzy-logic model to simulate habitat suitability indices of each life stage during the reproduction period. The last step of the modelling framework includes the aggregation of the dynamic habitat values to a temporally integrated parameter and the final result of the modelling framework, the reproduction habitat suitability.
The proposed multi-step habitat modelling framework is applied in a mountainous river reach downstream of a dam and produced reliable results. The simulated habitat suitability indices for each life-stage during reproduction allow for a representation of physical habitats in the form of spatial distribution maps for different time-steps, time-series for different locations and an integrated habitat supply over the entire reproduction period. This provides highly valuable information about habitat dynamics as all spatially and temporally varying input variables are considered in the multi-step habitat modelling framework. Consequently a direct identification of occurring bottlenecks during the reproduction of brown trout is feasible and can be referred back to responsible habitat variables. In the case study it is found that the spawning and emergence stages are not limiting the reproduction success and the most restricting conditions occurred during hatching. These limitations are predominantly caused by critical temperatures during the winter season and critical permeability conditions due to sediment infiltration processes during the regulated flow period. The aggregated reproduction habitat suitability contains the summarized effects of all varying abiotic conditions during the reproduction period of gravel-spawning fish and allows for a quick identification of the availability and quality of reproductive habitats.
Although the obtained results provide valuable results it is worth noting that models in general are never able to fully reflect the dynamic behaviour of rivers and its ecological relations given their numerous and complex interactions. The simplification of the physical and ecological processes requires a well-founded verification of obtained simulation results against field observations and reference sites. The highest benefit of the proposed modelling framework comprises the spatial and temporal consideration of conventional and new habitat variables resulting in a detailed representation of habitat dynamic processes occurring in river reaches. Further, the presented work is the first attempt to simulate the quality of reproduction habitats for gravel-spawning fish using physical habitat modelling. Possible future applications predominantly include the support of ecological impact assessments but also the applicability as an instrument supporting the management and planning processes of restoration measures (e.g. for re-establishing reproducing fish population in rivers) as the simulation of reproduction habitats presents one fundamental process for the development of stable fish populations.
Die Komplexitat und Dynamik fluvialer okologischer Prozesse stellt auserst hohe Anforderungen an die Entwicklung von Methoden und Modellen zur Unterstutzung in okologischen Bewertungen von Fliesgewassern. Insbesondere die Interaktion zwischen abiotischen und biotischen Komponenten, die hohe raumliche und zeitliche Variabilitat sowie die Interdisziplinaritat der beteiligten Prozesse erschweren die Entwicklung geeigneter Modellierungs- und Prognosewerkzeuge. Die regelmasige Erzeugung, Zerstorung und Erhaltung von charakteristischen Habitatmustern (Habitatdynamik) sind grundlegende Prozesse fluvialer Okosysteme, die mit aktuell verfugbaren Habitatmodellen schwierig abzubilden sind und die Notwendigkeit der Weiterentwicklung von existierenden Ansatzen der Habitatmodellierung verdeutlichen.
Die vorliegende Arbeit befasst sich mit Prozessen aus der Hydromorphologie, der Fliesge-wasserokologie und des hyporheischen Interstitials, die interaktiv die Habitatqualitat wahrend der Reproduktion von kieslaichenden Fischarten bestimmen. Die Motivation dieser Arbeit resultiert aus der wachsenden Anforderung dynamische Prozesse, wie die hydromorphologische und hyporheische Variabilitat in die physikalische Habitatmodellierung von Fischen zu implementieren um somit die Simulation von dynamisch veranderlichen Habitateignungen zu ermoglichen. Der Fokus richtet sich hierbei auf morphodynamische Prozesse, wie Kornsortierungen (longitudinal, horizontal und vertikal), Infiltration von Feinsedimenten in das Korngerust der Gewassersohle und Sohlumlagerungen, die einerseits notwendig sind um geeignete Habitate zu erzeugen aber andererseits auch limitierend wirken konnen. Um den Habitatanspruchen wahrend der Reproduktion durch Modellierung gerecht zu werden besteht weiterhin der Bedarf an der Entwicklung eines geeigneten Indikators zur Beschreibung der hyporheischen Variabilitat. Dieser soll dazu dienen den interstitialen Lebensraum wahrend den Entwicklungsstadien des Inkubationszeitraums (Augenpunktstadium, Schlupfzeit und larvale Phase) entsprechend zu bewerten. Das primare Ziel ist daher die Entwicklung eines Modellsystems, basierend auf dem Prinzip der physikalischen Habitatbeschreibung um die raumlich und zeitlich variierenden Habitateignungen der einzelnen Entwicklungsstadien wahrend der Reproduktionsphase von kieslaichenden Fischarten zu simulieren und zu einem aggregierenden Gesamtergebnis - der Reproduktionshabitateignung - zusammenzufuhren.
Das Modellsystem wird in einer typischen Gebirgsstrecke unterhalb einer Staumauer angewendet. Die Berucksichtigung von raumlich und zeitlich variierenden Habitatvariablen erlauben die simulierten Habitateignungen der einzelnen Entwicklungsstadien wahrend der Reproduktion kieslaichender Fische in Form von Habitateignungskarten zu verschiedenen Zeitpunkten, Habitateignungsganglinien an verschiedenen Orten und als integrierendes Habitatangebot darzustellen und auszuwerten. Damit wird einerseits die Habitatdynamik beschrieben und andererseits bieten die Auswertungen die Moglichkeit limitierende abiotische Randbedingungen sowohl zeitlich als auch raumlich zuzuordnen. Einschrankend ist jedoch festzuhalten, dass insbesondere der hyporheische Austausch in Zukunft verstarkt in der abiotischen Beschreibung der Habitate zu berucksichtigen ist und eine fundierte Uberprufung anhand biologischer Untersuchungen notwendig ist, um die Belastbarkeit der Ergebnisse zu erhohen.
Obwohl die erzielten Ergebnisse eine hohe Bedeutung fur die Bewertung der Reproduktion kiesaichender Fischarten beinhalten, bleibt festzuhalten, dass Modelle nie die gesamte fluviale Dynamik und deren Interaktion mit okologischen Prozessen abbilden konnen. Die Vereinfachung physikalischer und okologischer erfordern eine ausfuhrliche und wohlbedachte Verifizierung der erhaltenen Simulationsergebnisse anhand von Naturdaten und Referenzbedingungen. Die Weiterentwicklung der physikalischen Habitatmodellierung im Rahmen dieser Arbeit besteht masgeblich aus der raumlich und zeitlich hochaufgelosten Verwendung von bestehenden und neuen Habitatvariablen. Diese erlauben eine detaillierte Abbildung der relevanten abiotischen Prozesse in Fliesgewassern in ihrem zeitlichen Verlauf und somit Aussagen uber die Habitatdynamik. Des Weiteren stellt das Modellsystem erstmals den Versuch dar, die Reproduktionshabitate von kieslaichenden Fischarten im Rahmen einer physikalischen Habitatmodellierung abzubilden. Aufgrund der beinhalteten Dynamik und der Prognosefahigkeit des Modellsystems bestehen Anwendungsmoglichkeiten vorwiegend im Rahmen von okologischen Untersuchungen und Bewertungen, aber auch in der Planung und dem Management wasserwirtschaftlicher und wasserbaulicher Masnahmen, die zum Beispiel auf eine Wiedereinfuhrung von reproduzierenden Fischpopulationen abzielen, da die Simulation von verfugbaren Reproduktionshabitaten eine fundamentale Grundlage fur die nachhaltige Entwicklung von stabilen gewassertypischen Fischpopulationen ist.
45 citations
01 Jan 2009
TL;DR: In this article, a conceptual model is developed and implemented in a numerical model that is capable of modelling flow and transport processes considering structural alterations of the porous medium phenomenologically, and the structural alterations are accounted for phenomenologically by constitutive relations describing the impact of structural alterations on the flow and traffic behaviour.
Abstract: In this thesis, a conceptual model is developed and implemented in a numerical model that is capable of modelling flow and transport processes considering structural alterations of the porous medium phenomenologically. Thus, the model bridges the gap between pure flow and transport models on the one hand and structural mechanics models on the other hand.
The flow and transport model is a non-isothermal two-phase two-component model including advection and convection, diffusion, thermal conduction, vaporisation and condensation as well as dissolution and degassing. The structural alterations are accounted for phenomenologically by constitutive relations describing the impact of the structural alterations on the flow and transport behaviour. The following effects of the structural alterations are considered: immobilisation and mobilisation of water in the soil matrix, change in total volume and porosity as well as the impact the changes in total volume and porosity have on the hydraulically relevant processes. Based on a model-intercomparison study, it could be shown that the model can reproduce the flow and transport processes in a swelling soil and that the correct parameters can be determined by inverse modelling.
Stromungs- und Transportprozesse in schwellenden / schrumpfenden Boden, wie sie zum Beispiel in tonhaltigen Deponiebasisabdichtungen auftreten, werden masgeblich von den Strukturveranderungen des porosen Mediums beeinflusst.
Im Rahmen dieser Arbeit wird ein Modellkonzept entwickelt und in einem numerischen Modell implementiert, das sowohl Mehrphasenstromungs- und -transportprozesse in porosen Medien als auch Strukturveranderungen des porosen Mediums umfasst. Dabei handelt es sich um ein nichtisothermes Zweiphasen-Zweikomponenten-Model, das die Stromungs- und Transportprozesse Advektion und Konvektion, Diffusion, Warmeleitung, Verdunstung und Kondensation der Flussigphase sowie Losung und Entgasung der Gasphase einbezieht. Die Strukturveranderungen, deren Auswirkungen auf das Stromungs- und Transportverhalten phanomenologisch mittels konstitutiver Beziehungen berucksichtigt werden, sind Immobilisierung und Mobilisierung von Wasser in der Bodenmatrix, Anderung des Gesamtvolumens und der Porositat sowie deren Einfluss auf die hydraulisch relevanten Prozesse.
Zur Validierung des Modells wird eine Modellvergleichsstudie durchgefuhrt, die zeigt, dass erstens das Modell geeignet ist, die Stromungs- und Transportprozesse in schwellenden Boden zu simulieren, und zweitens alle dafur benotigten Parameter mittels inverser Modellierung korrekt bestimmt werden konnen.
40 citations
References
More filters
Book•
01 Jan 1989
TL;DR: Hosmer and Lemeshow as discussed by the authors provide an accessible introduction to the logistic regression model while incorporating advances of the last decade, including a variety of software packages for the analysis of data sets.
Abstract: From the reviews of the First Edition. "An interesting, useful, and well-written book on logistic regression models... Hosmer and Lemeshow have used very little mathematics, have presented difficult concepts heuristically and through illustrative examples, and have included references."- Choice "Well written, clearly organized, and comprehensive... the authors carefully walk the reader through the estimation of interpretation of coefficients from a wide variety of logistic regression models . . . their careful explication of the quantitative re-expression of coefficients from these various models is excellent." - Contemporary Sociology "An extremely well-written book that will certainly prove an invaluable acquisition to the practicing statistician who finds other literature on analysis of discrete data hard to follow or heavily theoretical."-The Statistician In this revised and updated edition of their popular book, David Hosmer and Stanley Lemeshow continue to provide an amazingly accessible introduction to the logistic regression model while incorporating advances of the last decade, including a variety of software packages for the analysis of data sets. Hosmer and Lemeshow extend the discussion from biostatistics and epidemiology to cutting-edge applications in data mining and machine learning, guiding readers step-by-step through the use of modeling techniques for dichotomous data in diverse fields. Ample new topics and expanded discussions of existing material are accompanied by a wealth of real-world examples-with extensive data sets available over the Internet.
35,847 citations
TL;DR: Applied Logistic Regression, Third Edition provides an easily accessible introduction to the logistic regression model and highlights the power of this model by examining the relationship between a dichotomous outcome and a set of covariables.
Abstract: \"A new edition of the definitive guide to logistic regression modeling for health science and other applicationsThis thoroughly expanded Third Edition provides an easily accessible introduction to the logistic regression (LR) model and highlights the power of this model by examining the relationship between a dichotomous outcome and a set of covariables. Applied Logistic Regression, Third Edition emphasizes applications in the health sciences and handpicks topics that best suit the use of modern statistical software. The book provides readers with state-of-the-art techniques for building, interpreting, and assessing the performance of LR models. New and updated features include: A chapter on the analysis of correlated outcome data. A wealth of additional material for topics ranging from Bayesian methods to assessing model fit Rich data sets from real-world studies that demonstrate each method under discussion. Detailed examples and interpretation of the presented results as well as exercises throughout Applied Logistic Regression, Third Edition is a must-have guide for professionals and researchers who need to model nominal or ordinal scaled outcome variables in public health, medicine, and the social sciences as well as a wide range of other fields and disciplines\"--
30,190 citations
TL;DR: In this article, the principles governing the application of the conceptual model technique to river flow forecasting are discussed and the necessity for a systematic approach to the development and testing of the model is explained and some preliminary ideas suggested.
19,601 citations
TL;DR: The Marquardt algorithm for nonlinear least squares is presented and is incorporated into the backpropagation algorithm for training feedforward neural networks and is found to be much more efficient than either of the other techniques when the network contains no more than a few hundred weights.
Abstract: The Marquardt algorithm for nonlinear least squares is presented and is incorporated into the backpropagation algorithm for training feedforward neural networks. The algorithm is tested on several function approximation problems, and is compared with a conjugate gradient algorithm and a variable learning rate algorithm. It is found that the Marquardt algorithm is much more efficient than either of the other techniques when the network contains no more than a few hundred weights. >
6,899 citations
TL;DR: The most important single factor involved in erosion phenomena and, in particular in connection with the development of stream systems and their drainage basins by aqueous erosion is called crossgrading.
Abstract: The composition of the stream system of a drainage basin can be expressed quantitatively in terms of stream order, drainage density, bifurcation ratio, and stream-length ratio.
Stream orders are so chosen that the fingertip or unbranched tributaries are of the 1st order; streams which receive 1st order tributaries, but these only, are of the 2d order; third order streams receive 2d or 1st and 2d order tributaries, and so on, until, finally, the main stream is of the highest order and characterizes the order of the drainage basin.
Two fundamental laws connect the numbers and lengths of streams of different orders in a drainage basin:
The infiltration theory of surface runoff is based on two fundamental concepts:
For a given terrain there is a minimum length x c of overland flow required to produce sufficient runoff volume to initiate erosion. The critical length x c depends on surface slope, runoff intensity, infiltration-capacity, and resistivity of the soil to erosion. This is the most important single factor involved in erosion phenomena and, in particular, in connection with the development of stream systems and their drainage basins by aqueous erosion.
The erosive force and the rate at which erosion can take place at a distance x from the watershed line is directly proportional to the runoff intensity, in inches per hour, the distance x , a function of the slope angle, and a proportionality factor K e , which represents the quantity of material which can be torn loose and eroded per unit of time and surface area, with unit runoff intensity, slope, and terrain.
The rate of erosion is the quantity of material actually removed from the soil surface per unit of time and area, and this may be governed by either the transporting power of overland flow or the actual rate of erosion, whichever is smaller. If the quantity of material torn loose and carried in suspension in overland flow exceeds the quantity which can be transported, deposition or sedimentation on the soil surface will take place.
On newly exposed terrain, resulting, for example, from the recession of a coast line, sheet erosion occurs first where the distance from the watershed line to the coast line first exceeds the critical length x c and sheet erosion spreads laterally as the width of the exposed terrain increases. Erosion of such a newly exposed plane surface initially develops a series of shallow, close-spaced, shoestring gullies or rill channels. The rills flow parallel with or are consequent on the original slope. As a result of various causes, the divides between adjacent rill channels are broken down locally, and the flow in the shallower rill channels more remote from the initial rill is diverted into deeper rills more closely adjacent thereto, and a new system of rill channels is developed having a direction of flow at an angle to the initial rill channels and producing a resultant slope toward the initial rill. This is called cross-grading.
With progressive exposure of new terrain, streams develop first at points where the length of overland flow first exceeds the critical length x c , and streams starting at these points generally become the primary or highest-order streams of the ultimate drainage basins. The development of a rilled surface on each side of the main stream, followed by cross-grading, creates lateral slopes toward the main stream, and on these slopes tributary streams develop, usually one on either side, at points where the length of overland flow in the new resultant slope direction first exceeds the critical length x c .
Cross-grading and recross-grading of a given portion of the area will continue, accompanied in each case by the development of a new order of tributary streams, until finally the length of overland flow within the remaining areas is everywhere less than the critical length x c . These processes fully account for the geometric-series laws of stream numbers and stream lengths.
A belt of no erosion exists around the margin of each drainage basin and interior subarea while the development of the stream system is in progress, and this belt of no erosion finally covers the entire area when the stream development becomes complete.
The development of interior divides between subordinate streams takes place as the result of competitive erosion, and such divides, as well as the exterior divide surrounding the drainage basin, are generally sinuous in plan and profile as a result of competitive erosion on the two sides of the divide, with the general result that isolated hills commonly occur along divides, particularly on cross divides, at their junctions with longitudinal divides. These interfluve hills are not uneroded areas, as their summits had been subjected to more or less repeated cross-grading previous to the development of the divide on which they are located.
With increased exposure of terrain weaker streams may be absorbed by the stronger, larger streams by competitive erosion, and the drainage basin grows in width at the same time that it increases in length. There is, however, always a triangular area of direct drainage to the coast line intermediate between any two major streams, with the result that the final form of a drainage basin is usually ovoid or pear-shaped.
The drainage basins of the first-order tributaries are the last developed on a given area, and such streams often have steep-sided, V-shaped, incised channels adjoined by belts of no erosion.
The end point of stream development occurs when the tributary subareas have been so completely subdivided by successive orders of stream development that there nowhere remains a length of overland flow exceeding the critical length x c . Stream channels may, however, continue to develop to some extent through headward erosion, but stream channels do not, in general, extend to the watershed line.
Valley and stream development occur together and are closely related. At a given cross section the valley cannot grade below the stream, and the valley supplies the runoff and sediment which together determine the valley and stream profiles. As a result of cross-grading antecedent to the development of new tributaries, the tributaries and their valleys are concordant with the parent stream and valley at the time the new streams are formed and remain concordant thereafter.
Valley cross sections, when grading is complete, and except for first-order tributaries, are generally S-shaped on each side of the stream, with a point of contraflexure on the upper portion of the slope, and downslope from this point the final form is determined by a combination of factors, including erosion rate, transporting power, and the relative frequencies of occurrence of storms and runoff of different intensities. The longitudinal profile of a valley along the stream bank and the cross section of the valley are closely related, and both are related to the resultant slope at a given location.
Many areas on which meager stream development has taken place, and which are commonly classified as youthful, are really mature, because the end point of stream development and erosion for existing conditions has already been reached.
When the end point of stream and valley gradation has arrived in a given drainage basin, the remaining surface is usually concave upward, more or less remembling a segment of a parabaloid, ribbed by cross and longitudinal divides and containing interfluve hills and plateaus. This is called a “graded” surface, and it is suggested that the term “peneplain” is not appropriate, since this surface is neither a plane nor nearly a plane, nor does it approach a plane as an ultimate limiting form.
The hydrophysical concepts applied to stream and valley development account for observed phenomena from the time of exposure of the terrain. Details of these phenomena of stream and valley development on a given area may be modified by geologic structures and subsequent geologic changes, as well as local variations of infiltration-capacity and resistance to erosion.
In this paper stream development and drainage-basin topography are considered wholly from the viewpoint of the operation of hydrophysical processes. In connection with the Davis erosion cycle the same subject is treated largely with reference to the effects of antecedent geologic conditions and subsequent geologic changes. The two views bear much the same relation as two pictures of the same object taken in different lights, and one supplements the other. The Davis erosion cycle is, in effect, usually assumed to begin after the development of at least a partial stream system; the hydrophysical concept carries stream development back to the original newly exposed surface.
5,348 citations