Cenozoic deposits in intermontane basins in the upper Gila River basin have been collectively included in the Gila conglomerate of Gilbert and Ransome. Re-examination of type-section areas shows that the term is unsatisfactory because it includes a substantial proportion of deposits other than conglomerates; it suggests that deposits in separate basins are identical; its use masks sequences of alluvial deposits within individual basins and relationships of deposits between basins; and it oversimplifies a complex Cenozoic history. It is suggested that the term Gila conglomerate be abandoned. The deposits, in the many basins, which heretofore may have been included in the Gila conglomerate, can be separated into two major divisions which may in turn be subdivided into mappable rock units. In each structural trough the upper units are characterized by: (1) Truncation by the highest pediment surfaces; (2) depositional or normal-fault contact with adjacent mountain areas whose composition the deposits reflect; (3) size-gradation relationships that suggest deposition within the boundaries of the present structural troughs; and (4) lack of mineralization. Limited fossil evidence suggests that deposition occurred during Pliocene to Pleistocene (Kansan) time. The lower units crop out in areas of deep dissection or structural uplift. They may be in fault contact with the upper units, underlie them unconformably, or grade into them. The lower units are characterized by: (1) Texture and composition that suggest deposition in basins other than those reflected by the present topography; (2) thrusting or normal faulting more complex than that associated with the upper units; (3) local mineralization; and (4) shallow intrusion. Limited fossil evidence sug gests a Miocene age for some of the older of the lower units, The alluvial deposits in individual basins in this area are amenable to stratigraphic analysis by standard procedures for describing rock units Correlations within or between basins should be on the basis of proper fossil or stratigraphic evidence and should be limited to the particular units involved and not expanded to include all the alluvial deposits in the areas concerned.

This thesis investigates the constant pressure cake filtration of interacting cellulose fibre/TiO2 (rutile) mixtures, and involved experimental studies using an automated pressure filtration apparatus. The influence of suspension composition, filtration pressure and solution environment on filtration has been discussed in relation to cake properties such as average cake porosity and specific resistance. To help interpret the filtration results, sedimentation data were also obtained. The average porosities of filter cakes formed from pure rutile and fibre suspensions in deionised water were approximately 0.6 and 0.75, respectively, and a steady and progressive increase in porosity with fibre fraction was generally observed. With filtrations at 450 kPa, the average specific cake resistances for pure fibre and rutile in deionised water were approximately 9.4x1013 and 4.2x1012 m kg-1 respectively, with the variation of specific resistance with solids composition showing a minimum. Similar trends were observed at other tested filtration pressures with suspensions in deionised water but not with filtrations of suspensions in 0.2 M NaCl and 0.1 M CaCl2 solutions. The minima in average specific cake resistance with solids composition for feeds in deionised water was attributed to rutile-fibre interactions. Abrupt transitions in cake structure were evident part way through some filtrations, and resulted in unexpected filtrate flow behaviour. This is an interesting phenomenon, and not only were the changes in cake structure relatively reproducible, but also the nature of the change could be altered by changes in filtration pressure, solids composition and/or solution environment. The study of fibre/particle binary filtration behaviour, in particular the porosity and specific cake resistance trends, were substantiated by relevant theoretical treatment and modelling analysis. With the porosity trends, an additive porosity concept seemed to represent the data better than interparticle penetration models. With the specific cake resistance trends, a semi-empirical equation was proposed which appeared to represent a wide range of binary mixture filtration data. A mathematical framework was also developed in an attempt to understand the underlying physical mechanisms which led to filter cake restructuring, and possible explanations were postulated.

The North Alpine Foreland Basin (NAFB) comprises sediments of late Eocene to middle Miocene age. The earliest deposits are the North Helvetic Flysch which are exposed in the regions of Glarus and Graubunden, eastern Switzerland. The Taveyannaz sandstones are the first thrust wedge (southerly) derived sediments of the North Helvetic Flysch. The Taveyannaz basin was divided into two sub-basins by a thrust ramp palaeohigh running ENE/WSW (parallel to the thrust front). Palaeocurrent directions were trench parallel towards the ENE. Sedimentation in the Inner basin (140m thick) is characterised by very thick bedded turbidite sands generated by thrust induced seismic events confined within the thrust-top basin. The Outer basin (240m min. thickness) comprises 10-15 sand packages (5-100m thick) formed by turbidite sands which are commonly amalgamated. Sedimentation in the Outer basin is considered to have been controlled by thrust-induced relative sea-level variations. The Inner basin underwent intense deformation at the sediment/water interface prior to the emplacement of a mud sheet over the basin whilst the sediments were partially lithified. Later tectonic deformation involved fold and thrust structures detaching in the underlying Globigerina marls. The stratigraphy of the NAFB can be considered as two shallowing upward megasequences separated by the base Burdigalian unconformity. This stratigraphy can be simulated by computer by simplifying the foreland basin/thrust wedge system into 4 parameters: 1) the effective elastic thickness of the foreland plate, 2) a transport coefficient to describe the erosion, transport and deposition of sediment, 3) the surface slope angle of the thrust wedge, 4) the thrust wedge advance rate. The Alpine thrust wedge underwent thickening during the underplating of the External Massifs at about 24-18Ma. This event is simulated numerically by slowing the thrust wedge advance rate, and increasing the slope angle and keeping all other parameters constant. This event causes rejuvenation of the forebulge, and erosion of the underlying stratigraphy, so simulating the base Burdigalian unconformity without recourse to eustasy or anelastic rheologies to the foreland plate.

We study a number of non-equilibrium models of interest to both active matter and biological physicists. Using microscopic agent-based simulation as well as numerical integration of stochastic PDEs, we uncover the non-trivial behaviour exhibited when active transport, or an advection field, is added to out of equilibrium systems. When gravity is included in the celebrated Fisher-Kolmogoro Petrovsky Piscouno (F-KPP) equation, to model sedimentation of active bacteria in a container, we observe a discontinuous phase transition between a `sedimentation' and a `growth' phase, which should in principle be observable in real systems. With the addition of multiplicative noise, the resulting model contains, as its limits, both the bacterial sedimentation previously described and the fluctuating hydrodynamic description of Directed Percolation (DP), an important and well-studied non-equilibrium system whose physics incorporate many universal features which are typical of systems with absorbing states. We map out the phase diagram describing all the systems in between these two limiting cases, finding that adding an advection term, however small, immediately lifts the resulting system out of the DP universality class. Furthermore, we find two distinct low-density phases separated by a dynamical phase transition reminiscent of a spinodal transition. Finally, we attempt to improve the current diffusion-limited model for the growth of filopodia, which are intriguing networks of actin fibres used by moving cells to sense their environment. By the addition of directed transport of actin monomers to the fibre tip complex by myosin molecular motors, we show that, under appropriate conditions, the resulting dynamics may be more efficient that transport by diffusion alone, which would result in filopodial lengths better corresponding to experimental observation.

To comply with the European Union Water Framework Directive (2000), National Governments are required to achieve good chemical and ecological status of freshwater bodies. Fine sediment has been shown to be a major cause of the degradation of lakes and rivers, and as a result research in geomorphology has been directed towards the understanding of fine sediment dynamics. It was identified by a review of published literature that at present a paucity of information on sediment dynamics existed for the East Midlands, UK. The use of tracers within a sediment fingerprinting framework has recently become a heavily used technique to investigate the sources of fine sediment pressures. However, uncertainties associated with tracer behaviour have been cited as major potential limitations to sediment fingerprinting methodologies. At present few studies have quantified the uncertainties associated with tracer use, or the exact reasons why different tracers are producing different sediment provenance results. This thesis had two aims based on these gaps in published literature. First, to assess the impact of sediment sampling methodology, tracer selection, particle size corrections and organic enrichment corrections on a fine sediment fingerprinting study. Secondly, to develop a partial sediment budget for the Upper Nene river basin and its major tributaries. The results of this thesis were presented in two parts. The first part investigated Aim 1 when fingerprinting; historically deposited sediment, suspended sediment and recently deposited sediment. The second part investigated Aim 2 by constructing a fine sediment budget for the Nene river basin, consisting of; sediment yield, sediment provenance, floodplain sediment accumulation and channel bed sediment storage. A mean difference of 24.1% between the predicted contributions of sediment originating from channel banks was found when using nine different tracer groups to fingerprint the river sediment samples. When fingerprinting contributions from urban street dusts mean differences between tracer group predictions were lower, at between 8% and 11%. There was little indication that organic matter content and / or particle size caused differences between tracer group predictions. Within-source variability in tracer concentrations, and small contrasts between the tracer concentrations of the sediment source groups, were identified as probable causes of inherent uncertainty present in the fingerprinting analysis. It was determined that the ratio of the percentage difference between median tracer concentrations in the source groups and the average within-source tracer concentration coefficient of variation could indicate the likely uncertainty in model predictions prior to tracer use. When fingerprinting historically deposited sediment, a reservoir core was fingerprinted with the least uncertainty, with tracer group provenance predictions ~28% apart and with consistent down-core trends. When fingerprinting an on-line lake core and four floodplain cores, differences between tracer group predictions were as large as 100%; the down-core trends in changing sediment provenance were also different. The differences between tracer group predictions could be attributed to the organic matter content and particle size of the sediment. There was also evidence of the in-growth of bacterially derived magnetite and chemical dissolution affecting the preservation of tracer signatures. Despite the prior indications that organic matter and particle size were causing tracer non-conservatism in historical sediment cores, data corrections were found to often be ineffective at reducing the differences between tracer group predictions. The corrections were found to either have no effect on, or increase the mean differences between, tracer group predictions when fingerprinting river sediment. The sediment budget identified that the annual sediment yield of 13 - 19 t km-2 yr-1 for the Nene is low in comparison to other UK catchments. Channel banks were found to be the dominant sediment source in the Nene, typically contributing between 60% and 100% of the sediment. Rates of sediment accumulation on the Nene’s floodplain was found to be highly variable (920– 7,200 t km-2 yr-1); the presence of flood defences were likely to be a cause of this variability, and have caused a reduction in the accumulation rate since 1963. It was found that large quantities of sediment accumulated on channel beds during periods of low flows (~ 28% of the annual sediment yield), which was flushed from the bed by a series of flood events (leaving <1% of the annual sediment yield in temporary storage). An original contribution to research was made by quantifying the uncertainties associated with tracer use in a fine sediment fingerprinting investigation, as well as identifying the probable causes of the observed uncertainty. The fine sediment dynamics of the Nene basin were also investigated for the first time, and it was identified that the high contributions from channel banks in the Nene were highly a-typical for UK catchments.

The central objective of the study was to fractionate sedimenting organic materials according to their source (allochthonous or autochthonous) and ultimately to determine the degree of biodegradability of contributions from either source with particular reference to activities at the mud-water interface.

Coastal marshes and wetlands are vital natural resources that offer habitats for plants and animals, serve as ecological filtration for soil and water pollutants, and act as protection for coastlines. Fishing, both commercial and sport, has a large economic impact in the study area – the Gulf Coast between Galveston Bay, TX and Oak Grove, LA. The objective of this research was to determine the contribution of Hurricane Ike storm surge sedimentation to long-term marsh aggradation in Texas and Louisiana coastal marshes. The research hypothesized that Hurricane Ike’s storm surge deposit would be equal to decades and possibly even a century’s worth of the average annual non-storm sedimentation. A quantitative field study was performed. The storm surge deposit was examined in a series of 15 transects covering approximately 180 km east of Hurricane Ike’s landfall. Nine of the 15 transects were re-surveyed a year after the initial measurement to assess preservation of the deposit. The results demonstrate that Hurricane Ike contributed between 10 to 135 years’ worth of sediment to coastal marshes along the coasts of Texas and Louisiana, and the sediment deposits have been preserved for over two years.

The Skeleton Coast forms part of the Atlantic coastline of NW Namibia comprising several ephemeral rivers, which flow west-southwest towards the Atlantic Ocean. The area is hyper-arid with less than 50 mm average annual rainfall and a rainfall variability of 72%. Therefore, the major catchment areas of the rivers are about 100-200 km further inland in regions with relatively high annual rainfall of 300-600 mm. The coastal plain in the river downstream areas is characterized by a prominent NNW trending, 165 km long belt of 20-50 m high, locally compound, barchanoid and transverse dunes. This dune belt, termed Skeleton Coast Erg, starts abruptly with a series of barchans and large compound dunes 15 km north of the Koigab River and extends from 2-5 km inland sub-parallel to the South Atlantic margin of NW Namibia over a width of 3-20 km. As the SSE-NNW trending dune belt is oriented perpendicular to river flow, the dunefield dams and interacts with the west-southwestward flowing ephemeral river systems. This study focused on three main topics: 1) investigation and classification of the Koigab Fan, 2) the investigation of the Cenozoic succession in the Uniabmond area and 3) comparative studies of fluvio-aeolian interaction between five ephemeral rivers and the Skeleton Coast Erg. Sedimentological and geomorphological investigations show that the Koigab Fan represents a yet undocumented type of a braided fluvial fan system, which operates in an arid climatic, tropical latitude setting, is dominated by ephemeral mixed gravel/sand braided rivers, lacks significant vegetation on the fan surface, has been relatively little affected by human activity, is a perfect study site for recording various types of fluvio-aeolian interaction and thereby acts additionally as a model for certain Precambrian and Early Palaeozoic fan depositional systems deposited prior to the evolution of land plants. The Cenozoic succession in the Uniabmond area consists of three major unconformity-bounded units, which have been subdivided into the Red Canyon, the Whitecliff, and the Uniabmond Formation. The Tertiary Red Canyon Fm. is characterized by continental reddish sediments documenting an alluvial fan and braided river to floodplain depositional environment. The Whitecliff Fm. displays a wide variety of continental and marine facies. This formation provides the possibility to examine fluvio-aeolian interactions and spectacular, steep onlap relationships towards older sediments preserved in ancient seacliffs. The Whitecliff Fm. has been subdivided into four sedimentary cycles, which resulted from sea level changes during the Plio- to Middle Pleistocene. The following Uniabmond Fm. provides a unique insight into the depositional history of the NW Namibian coast during the Last Pleistocene glacial cycle. The formation has been subdivided into four units, which are separated by unconformities controlled by sea level changes. Unit 1 represents deposits of an Eemian palaeo-beach. The overlying Units 2-4 build up the sedimentary body of the Uniab Fan, again a braided river dominated fan, which is nowadays degraded and characterized by deeply incised valleys, deflation surfaces and aeolian landforms. The Uniabmond Fm. is overlain by the dunes of the Skeleton Coast Erg, whose development is related to the Last Glacial Maximum (LGM). The damming of river flow by aeolian landforms has been previously recognized as one of several principal types of fluvio-aeolian interaction. Five ephemeral rivers (from S to N: Koigab, Uniab, Hunkab, Hoanib, Hoarusib), which variously interact with the Skeleton Coast Erg, were chosen for the purpose of this study to consider the variability of parameters within these fluvio-aeolian systems and the resulting differences in the effectiveness of aeolian damming. The fluvio-aeolian interactions between the rivers and the dune field are controlled by the climate characteristics and the geology of the river catchment areas, the sediment load of the rivers, their depositional architecture, the longitudinal river profiles as well as the anatomy of the Skeleton Coast Erg. Resulting processes are 1) aeolian winnowing of fluvially derived sediments and sediment transfer into and deposition in the erg; 2) dune erosion during break-through resulting in hyperconcentrated flow and intra-erg mass flow deposits; 3) the development of extensive flood-reservoir basins caused by dune damming of the rivers during flood; 4) interdune flooding causing stacked mud-pond sequences; and 5) the termination of the erg by more frequent river floods. / Das hyperaride Gebiet der Skelettküste im NW Namibias ist durch eine Vielzahl ephemerer Flußsysteme und einen über 165 km langen, NNW-streichenden Dünengürtel, den Skelettküsten-Erg, charakterisiert. Der Erg verläuft nahezu orthogonal zu den westwärts, zum Atlantik entwässernden ephemeren Flußsystemen, deren Haupteinzugsgebiete etwa 150-300 km östlich der Küste liegen. Bei ihrem unregelmäßigen Abkommen auf dem Weg zum Atlantischen Ozean müssen die meisten dieser westwärts entwässernden Riviere den Dünengürtel passieren. Aus diesem Grund wurde dieses Gebiet ausgewählt, um vergleichende sedimentologische und geomorphologische Studien durchzuführen, die sich auf folgende frei Schwerpunkte konzentrierten: 1) die Untersuchung und Klassifizierung des Koigab Fans und dessen Rolle für den Sedimenteintrag in den Skelettküsten Erg; 2) die detaillierte Aufnahme und Untersuchung der känozoischen Sedimente im Mündungsbereich des Uniab Riviers und deren Rolle bei der Interpretation von Plio- und Pleistozänen Meeresspiegelschwankungen; und 3) die Erlangung eines grundlegenden Verständnis der zugrundeliegenden Kontrollparameter für die Variabilität von fluvio-äolischen Interaktionen und der daraus resultierenden Sedimentkörpergeometrien. Im Mündungsbereich des Koigab Riviers befindet sich der Koigab Fan. Dieser ist mit einer Länge von 15 km und einer Breite von 21 km der größte aktive Fan der Skelettküste, der durch einen der westsüdwestwärts entwässernden ephemeren Flußsystemen gebildet wurde. Sedimentologische und geomorphologische Studien an dessen Ablagerungen ergaben, dass es sich bei ihm um einen bis jetzt noch nicht dokumentierten Fan-Typ innerhalb der bestehenden Fan-Klassifikationen handelt. Der Koigab Fan repräsentiert einen von verflochtenen ephemeren Flußrinnen aufgebauten Fan, der keine Anzeichen von Schuttstömen (debris flows) oder mäandrierenden Flußrinnen aufweist. Der Koigab-Fan stellt daher ein Endglied innerhalb des von Stanistreet & McCarthy (1993) zur Fan-Klassifikation aufgestellten Dreieckdiagramms dar. Dem Koigab-Fan kommt eine besondere Bedeutung zu, da er in Bezug auf Größe und Gradienten eine Brücke zwischen der Gruppe kleiner, steil abfallender Fans und den mit nur geringem Gefälle versehenen Mega-Fans schlägt. Trotz seiner Position in den Tropen liegt der Koigab-Fan in einem ariden Gebiet und ist durch eine ausgeprägte Vegetationsarmut gekennzeichnet. Sedimentologische Untersuchungen an seinen Ablagerungen können daher auch als Analogbeispiele für vegetationsfreie früh-proterozoische und früh-paläozoische Fan-Systeme verwendet werden. Zudem stellt der Koigab Fan eine wesentliche Sedimentquelle für den Skelettküsten Erg dar, was mit Hilfe von Schwermineral- und Korngrößenanalysen nachgewiesen werden konnte. Die im Mündungsbereich des Uniab Riviers anstehenden Sedimente stellen die am vollständigsten erhaltene und am besten aufgeschlossene känozoische Sedimentabfolge entlang der Küste NW-Namibias dar. Im Rahmen des Promotionsprojektes wurde diese Abfolge erstmals vollständig sedimentologisch bearbeitet und anhand markanter Diskordanzen in drei Formationen unterteilt: die Red Canyon, Whitecliff und Uniabmond Formation. Die tertiäre Red Canyon Fm. ist durch Rotsedimente charakterisiert, die in einem alluvial-fluvialen Milieu abgelagert wurden. Die überlagernde Whitecliff Fm. wird aus vier sedimentären Einheiten aufgebaut. Die älteste und die jüngste Einheit enthalten marine und äolische Ablagerungen, in denen fossile Strandniveaus überliefert sind. Diese können herangezogen werden um die Whitekliff Fm. in das späte Pliozän bis ins mittlere Pleistozän einzustufen. Mit den Sedimenten der Uniabmond Fm. ist höchst wahrscheinlich der letzte glaziale Zyklus des Pleistozäns überliefert. Die jüngsten Sedimente der Uniabmond Fm. werden direkt von dem Skelettküsten Erg überlagert, dessen Bildung mit dem letzten glazialen Meeresspiegel-Tiefstand zusammenfällt. Das Aufstauen von Flüssen durch Dünen stellt einen Haupttyp fluvio-äolischer Interaktion dar. Fünf ephemeren Flusssystemen, die unterschiedlich mit dem Skelettküsten Erg in Interaktion treten, wurden innerhalb dieser Studie eingehen untersucht, um die Bandbreite fluvio-äolischer Interaktionen und deren zugrundeliegenden Kontrollparameter zu erfassen. Die fluvio-äolischen Interaktionen zwischen den Flüssen und dem Dünenfeld werden kontrolliert durch Klimacharakteristika, die Geologie des Einzugsgebietes, die Sedimentfracht der Flüsse, ihre Ablagerungsarchitektur und die Anatomie des Skelettküsten Ergs. Die zu beobachtenden Prozesse sind 1) äolische Verfrachtung von fluvial antransportiertem Sediment und dessen Ablagerung in dem Erg; 2) die Erosion und Aufarbeitung von Dünen während Durchbruchsereignissen; 3) die Bildung ausgedehnter Stauseen; 4) die Flutung von Interdünenbereichen mit der Ablagerung von Ton-Silt-Abfolgen; und 5) die Termination des Ergs durch häufiger auftretende Fluten.

Thesis advisor: Noah P. Snyder / Thesis advisor: Gabrielle C. David / The Reservoir Sedimentation Database (ResSed), a catalogue of reservoirs and depositional data that has recently become publicly available, allows for rapid calculation of sedimentation and capacity-loss rates over short (annual to decadal) timescales. This study is a statistical investigation of factors controlling average sediment yield (Y) in eastern United States watersheds. I develop an ArcGIS-based model that delineates watersheds upstream of ResSed dams and calculate drainage areas to determine Y for 191 eastern US watersheds. Geomorphic, geologic, regional, climatic, and land use variables are quantified within study watersheds using GIS. Sediment yield exhibits a large amount of scatter, ranging from 4.7 to 3336 tonnes1km 2year-1. A weak inverse power law relationship between drainage area (A) and Y (R2 = 0.09) is evident, similar to other studies (e.g., Koppes and Montgomery, 2009). Linear regressions reveal no relationship between mean watershed slope (S) and Y, possibly due to the relatively low relief of the region (mean S for all watersheds is 6°). Analysis of variance shows that watersheds in formerly glaciated regions exhibit a statistically significant lower mean Y (159 tonnes1km-2year-1) than watersheds in unglaciated regions (318 tonnes1km-2year-1), while watersheds with different dam purposes show no significant differences in mean Y. Linear regressions reveal no relationships between land use parameters like percent agricultural, and percent impervious surfaces (I) and Y, but classification and regression trees indicate a threshold in highly developed regions (I > 34%) above which the mean Y (965 tonnes1km-2year-1) is four times higher than watersheds in less developed (I < 34%) regions (237 tonnes1km 2year-1). Further, interactions between land use variables emerge in formerly glaciated regions, where increased agricultural land results in higher rates of annual capacity loss in reservoirs (R2 = 0.56). Plots of Y versus timescale of measurement (e.g., Sadler and Jerolmack, 2014) show that nearly the full range of observed Y, including the highest values, are seen over short survey intervals (< 20 years), suggesting that whether or not large sedimentation events (such as floods) occur between two surveys may explain the high degree of variability in measured rates. / Thesis (MS) — Boston College, 2014. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

Visando garantir a disponibilidade hídrica em seus diferentes usos são construídos reservatórios, estes sempre associados a problemas de perda de volume de armazenamento devido ao processo de assoreamento. A atualização destes dados, bem como a quantificação do assoreamento geralmente é feita através de Levantamento Batimétrico. Apesar da grande importância do tema não é observado na literatura um método padronizado para a realização de estudos batimétricos, autores e organizações apresentam métodos dispares quanto à quantidade e disposição dos dados. Deste modo, a presente pesquisa buscou elencar os métodos apresentados na literatura e analisá-los quanto a precisão obtida no cálculo de volume do reservatório, utilizando como estudo de caso o reservatório da UHE Três Irmãos (SP). Observou-se que os MDTs gerados pelos métodos não representavam com fidelidade trechos estreitos do reservatório (braços) bem como o talvegue. Foi então proposto um método para a determinação do espaçamento entre seções bem como uma rotina para geração de MDT considerando características do talvegue. O método proposto para determinação do espaçamento entre seções se mostrou capaz de representar com relativa boa precisão trechos dos braços (diferença máxima encontrada de 5,01%) e apresentou tempo de coleta de dados de 60% do método mais preciso apresentado na literatura. A rotina de geração de MDT proporcionou em média melhora de aproximadamente 30% na qualidade dos dados de volume calculados. Por meio da aplicação dos métodos desenvolvidos na UHE Chavantes foi calculado um assoreamento de 3,91%, de acordo com os resultados, sem a utilização das rotina de geração de MDT desenvolvida cálculo do volume do reservatório seria subestimado em 1,61%, superestimando o cálculo do assoreamento. / Water reservoirs are built with the main purpose of guaranteeing water supply, however, their volume always decreases due the sedimentation processes. Bathymetric surveys can be deployed to assess the current volumetric capacity of a given reservoir and to estimate and quantify the sedimentation process. Although Bathymetric surveys are considered to be a key factor when analyzing and assessing properties of a given reservoir, a standard method for its deployment is yet to be defined. Authors and research groups presents different methods about the sampling rate as well as the choice of adequate spots for data collection. The overall goal of this research was to identify and analyze the different methods deployed in previous published literature analyzing the accuracy of the volume data provided by these different methods. Três Irmãos reservoir (São Paulo) was used as a case study where methods were compared. It was pointed out that the DEMs obtained were unable to accurately represent narrower reservoirs areas (tributaries) and the thalweg. Therefore was proposed a new method for determining the distance among survey sections as well as a routine for DEM generation takes into account the thalweg characteristics. Results revealed that the data pulled out was able to represent with accuracy the tributary areas (maximum difference was 5.01%). In addition, a reduced data collection time was observed (60%) when compared against the most accurate method found in published literature. The proposed technique for DEM generation indicated approximately 30% of quality improvement in the data calculated for the reservoir volume. The developed method was applied on a bathymetric survey conducted on the Chavantes reservoir (São Paulo). The loss of reservoir capacity assessed was 3.19%. According to results, a bathymetric survey which does not deploy the new method proposed would underestimate the reservoir\'s volume by 1.61% and overestimate the sedimentation process.