Since 1936 National Park Service has been charged with preserving Civil War Earthworks while allowing public access. Soil erosion, both natural and human-induced, is a major concern facing the preservation of the earthworks. Currently, the National Park Service is committed to preserving these earthworks for future generations by determining which maintenance activities cause the least soil erosion. This study was undertaken to determine which management practice; burned, mowed, park-forest, forested, or trimmed, best minimized soil erosion. A secondary objective was to determine how several empirical formulas (e.g. Universal Soil Loss Equation) and one field estimate (e.g. erosion pins) compared soil erosion trends for the 5 treatments. A third objective of this study was to gather information regarding the soil development which has occurred during the 135 + years since the earthworks were constructed. Earthworks managed by prescribed burning suffered the greatest erosion rates while the forested earthworks eroded the least. The trimmed and mowed management regimes were not significantly different and would provide adequate erosion protection while the forested treatment had significantly less erosion. Based on the empirical models, erosion was primarily a function of ground cover; on the other hand, rain intensity was highly influential for erosion as measured by the erosion pins. All of the erosion estimation methods concurred that the burned treatment should be avoided due to the high erosion rates while the erosion pins indicated that the park-forest treatment could potentially have erosion problems as well. Soil profile descriptions from the earthworks revealed that A horizon depths on the earthworks were not significantly different then the A horizons found on the relatively undisturbed adjacent forest floor and that subsurface soil structure has begun to develop on earthwork soils. / Master of Science

To quantify sediment contributions due to urban channel enlargement, 50 study sites were selected on 1st- through 3rd-order streams, in watersheds with varying levels of urbanization, in two Physiographic Regions (Coastal Plain and Piedmont), and in the Coastal Zone Management Area of Virginia. At each site, riffle cross-sectional and longitudinal surveys were conducted to measure the channel morphology. Enlargement ratios for bankfull cross-sectional parameters were calculated to quantify channel change relative to stable streams (from regional curves). Relationships between dependent, channel characteristics and watershed-scale, independent variables were assessed. The main objectives were to: 1) test for differences in the morphological features between Coastal Plain and Piedmont streams; 2) develop relationships between watershed-level, urbanization characteristics and stream morphological features; and, 3) determine if relationships exist between watershed urbanization and channel enlargement ratios to estimate sediment loading from urban streams for use in statewide nonpoint source pollution assessment activities. It was determined that: 1) for a given watershed area, streams in the Piedmont tended to be larger than those in the Coastal Plain Region (for regional curve streams and for project streams); 2) among all project sites and sites in the Piedmont, watershed area was the best indicator of channel morphology, but among the Coastal Plain sites, the number of road crossings over streams was the best indicator of channel morphology; and, 3) few significant relationships between enlargement ratios and watershed urbanization variables existed; however, one commonality observed across all sites was an inverse relationship between watershed area and channel enlargement ratios. / Master of Science

Accurately predicting sediment delivery has been a long-standing problem in the field of water resource management. Many different watershed equations and models have been developed such as the Universal Soil Loss Equation (USLE), the Geo-spatial interface for the Water Erosion Prediction Program (GeoWEPP) and many more, however, these models have not always been able to reliably predict in-stream sediment loads. In this study, two scales, watershed and site level, are used to understand where sediment transported in-stream is being produced. At the watershed scale, USLE was used to estimate sediment yield and then different factors such as connectivity topographic indices were applied as discount factors in an attempt to improve these estimates. The different parameters were then compared to turbidity to determine the level of accuracy of each method. It was found that USLE is not able to predict in-stream turbidity levels in the study area watersheds in Virginia and North Carolina. An implicit assumption of USLE is that runoff is produced on steeper slopes and that sediment production occurs on these hillslopes. However, it was found that flatter-sloped areas were highly correlated with in-stream turbidity. It was also found that in-channel and site-specific parameters such as bank height/slope and level of confinement at higher flows were more accurate predictors of in-stream sediment levels. Overall, turbidity and in-stream sediment levels are not well predicted by models that employ USLE. The distribution of runoff source areas, and channel/bank properties appear to be good predictors of sediment production at the watershed scale. These results indicate that sediment production and transport, as conceptualized by common models and equations, often associate sediment source areas with geomorphic and hydrologic processes in ways that are not consistent with the results of this study. Our results show that sediment is most likely being sourced from the channels and in stream areas. / Master of Science / Predicting how sediment moves through a watershed has been a long-standing problem in the field of water resource management. There are many equations and models that have been developed to calculated the amount of sediment that exits a watershed; such as the Universal Soil Loss Equation (USLE), the Geo-spatial interface for the Water Erosion Prediction Program (GeoWEPP) and many more. However, these models have not always been reliable or accurate in their predictions. In this study, two scales, watershed and site level, are used to understand where sediment transported within streams is being produced. At the watershed scale, USLE was used to estimate sediment leaving a system and then different factors, with different approaches to the understanding of sediment movement, were applied as discount factors in an attempt to improve these estimates. The different values that were calculated were then compared to turbidity to determine the level of accuracy of each parameter. It was found that USLE is not able to predict in-stream turbidity levels in the study area watersheds in Virginia and North Carolina. An assumption of USLE is that runoff is produced on steeper slopes and that sediment erosion occurs on these steeper sloped areas. However, it was found that flatter-sloped areas were highly correlated with turbidity. It was also found that in-channel and site-specific parameters such as bank height/slope and the level of confinement at higher flows were more accurate predictors of turbidity. Overall, USLE and models that used USLE were not able to predict turbidity. The distribution of runoff source areas and channel/bank properties appear to be good predictors of turbidity at the watershed scale. These results indicate that sediment movement, as conceptualized by common models and equations, often associate sediment source areas with watershed level morphology and hydrology in ways that are not consistent with the results of this study. Our results show that sediment is most likely being produced from the channels and in stream areas.

Doctor of Philosophy / Environmental Design and Planning Program / Timothy D. Keane / The original purpose of this investigation was to develop streambank erosion prediction curves for Northeast Kansas streams. Rosgen's (2001, 2006) methods were employed and eighteen study banks were measured and monitored over a four-year period, summer 2007 through summer 2010. At each study bank, a toe pin and two to three bank pins were set at a recorded longitudinal profile station of the stream. Vertical and horizontal measures from the toe pin to the bank face were taken each summer, 2007 as the baseline measure and 2008 - 2010 as bank change years. Bank profiles were overlaid to gain insight into bank area lost or gained due to erosional or depositional processes. A Bank Erosion Hazard Index (BEHI) and Near Bank Stress (NBS) combination rating was assessed and calculated for each study bank during the initial survey of 2007. The streambanks experienced varied erosion rates for similar BEHI/NBS combinations producing R2 values from 0.43 as the High/Very High BEHI rating and 0.80 as the Moderate BEHI rating. In addition, Moderate BEHI ratings provided higher erosion rates than the High/Very High BEHI rating and curves intersected at lower NBS ratings, suggesting a discrepancy in the fit of the model used in the Northeast Kansas region and conditions. In this light, modification of the BEHI model was evaluated and variables were assessed in the model for additional influence exerted in the Northeast Kansas region. Vegetation seemed to provide the most influence to bank resistance and was more closely evaluated. Banks with and without woody riparian vegetation were then plotted against BEHI and NBS values, as banks lacking woody vegetation eroded at higher rates. This study's findings can allow us to calibrate the BEHI model according to woody vegetation occurrence levels along streambanks in the Black Vermillion watershed. Modifications regarding vegetation occurrence of the BEHI model was completed and the results of these modifications generated R2 values of 0.78 for High/Very High BEHI and 0.82 for Moderate BEHI ratings. High/Very High ratings provided higher predicted erosion rates than Moderate ratings, while the curve slopes did not intersect at lower NBS ratings.

Dans cette thèse je travaille sur la relation entre la pluviosité et l’érosion fluviatile en utilisant une approche probabiliste. Je développe une méthodologie indépendante de la moyenne pour caractériser la variabilité de la pluviosité journalière.L’indépendance vis-à-vis de la moyenne permet une comparaison simpleetobjectivedelavariabilitédelapluviosité sous différents régimes climatiques. Elle semontre également utile pour intégrer le concept de variabilité de la pluviosité dans lathéorie que je développe ensuite. J’applique cette approche à la chaine de montagnesHimalayenne en utilisant des données de pluviosité de hautes résolutions spatiale ettemporelle et trouve qu’il existe des variations significatives de la variabilité de la pluviositédans l’Himalaya. En prenant en compte la variabilité de la pluviosité en plusde la pluviosité moyenne, je trouve un lien entre pluviosité et érosion qui, d’un pointde vue géomorphologique, diffère, de façon significative, de celui déduit de la seulepluviosité moyenne.Ensuite, je développe une théorie d’érosion fluviatile du type ’puissance de flux‘ quicomprend une paramétrisation réaliste de la pluviosité et de l’hydrologie. Ceci estréalisé en intégrant un modèle hydrologique stochastique-mécaniste bien établi dansune formulation stochastique de la puissance de flux comprenant un seuil. La théoriehydrologique conduit à des expressions mathématiques pour la distribution et la variabilitédu débit journalier en fonction des conditions climatiques qui sont valablespour la majorité des régimes de débit observés à la surface de la Terre. Les nouveauxparamètres qui en découlent ont une signification bien ancrée dans des théories climatiqueet hydrologique établies et se mesurent facilement. Cette approche nous permetde prédire comment le taux d’érosion fluviatile répond à des changements du forçageclimatique. Je trouve ainsi que les processus hydrologiques peuvent avoir une influencesignificative sur l’efficacité érosive d’un forçage climatique donné. Cette approchepeut également être utilisée comme fondement de nouveaux modèles d’évolution desreliefs qui prennent en compte des conditions aux limites climatique et hydrologique.Une des principales conséquences d’intégrer l’hydrologie dans le modèle de puissancede flux est de révéler le double effet de la moyenne et de la variabilité du forçage climatiquesur la réponse écohydrologique. Une corrélation négative existe entre la moyenneet la variabilité qui restreint grandement les réponses possibles d’un bassin versant àdes changements climatiques. L’approche théorique que j’ai développée décrit égalementles relations qui relient la variabilité journalière à plusieurs paramètres écohydroclimatiques.Je trouve ainsi que l’index d’aridité, le temps de réponse du bassin versant,et l’épaisseur effective de sol sont les contrôles les plus importants sur la variabilité dudébit. Ceci a d’importantes conséquences pour le rôle que jouent l’hydrologie et lavégétation sur l’évolution des reliefs.Finalement, je démontre que l’influence de la variabilité journalière du forçage climatiquesur le taux d’érosion des rivières est principalement déterminée par l’existence et la valeur de seuils d’érosion. Je démontre que, quelques soient les détails du processus d’érosion considéré, c’est le rapport entre la valeur du seuil et la valeur moyenne du forçage climatique qui détermine si la variabilité compte ou pas, et dans quel sens.Parmi de nombreuses autres applications, ces découvertes contribuent à l’élaborationd’un nouveau cadre permettant de comprendre et prédire la réponse de la surface dela Terre à des changements de la moyenne et de la variabilité de la pluviosité et du débit des rivières. La généralité de ces découvertes a d’importantes implications pour le reste des travaux présentés dans la thèse, ainsi que pour les travaux antécédents sur le rôle de la variabilité de la pluviosité et du débit sur l’efficacité érosive des rivières. / In this thesis, we address the problem of how climate drives landscape evolution. Specifically, we work on the relationship between rainfall and fluvial erosion using a probabilistic approach. First we develop a mean-independent methodology to characterize the variability of daily rainfall. The mean-independent nature allows for simple, objective comparison of rainfall variability in climatically different regions. It also proves useful for integrating the concept of rainfall variability into theory. We apply this method over the Himalayan orogen using high spatial and temporal resolution rainfall data sets and find significant variations in rainfall variability over the Himalayan orogen. By taking into account variability of rainfall in addition to mean rainfall rate, we find a pattern of rainfall that, from a geomorphological perspective, is significantly different from mean rainfall rate alone. Next we develop of theory of stream power fluvial erosion that allows for realistically parameterized rainfall and hydrology. This is accomplished by integrating an established stochastic-mechanistic model of hydrology into a threshold-stochastic formulation of stream power. The hydrological theory provides equations for the daily streamflow distribution and variability as a function of climatic boundary conditions that are applicable across most of the observed range of streamflow regimes on Earth. The new parameters introduced are rooted firmly in established climatic and hydrological theory and are easily measured. This framework allows us to predict how fluvial erosion rates respond to changes in realistic rainfall forcing. We find that hydrological processes can have a significant influence on how erosive a particular climatic forcing will be. This framework can be used as a foundation for landscape evolution models that have realistic climatic and hydrological boundary conditions. One of the main strengths of integrating hydrology into the stream power model is to reveal the dependence of both streamflow mean and variability on the climatic forcing and ecohydrological response. This negative correlation of the mean and variability vastly restricts the likely responses of a river basin to changing climate. Our theoretical framework also describes the scaling daily variability with several other ecohydroclimatic parameters. We find that the aridity index, the basin response time, and the effective soil depth are the most important controls on discharge variability. This has important implications for the role of hydrology and vegetation in landscape evolution. Finally, we demonstrate that the way the Earth's surface responds to short-term climatic forcing variability is primarily determined by the existence and magnitude of erosional thresholds. We show that, irrespective of the nature of the erosional process, it is the ratio between the threshold magnitude and the mean magnitude of climatic forcing that determines whether variability matters or not and in which way. Among many other implications, our findings help provide a general framework to understand and predict the response of the Earth's surface to changes in mean and variability of rainfall and river discharge. The generality of this finding has important implications for the other work in this thesis, as well as previous work on role of rainfall and discharge variability on fluvial erosion.

This thesis focuses on the great threat of soil erosion. We live in a fast moving world where roads, motorways, and buildings are being built with no regard to soil protection. Soil erosion is faster and more visible. This thesis analyses and compares anti-erosion protection strategies of particular areas according to the land consolidation proposed by Land Registry, or according to a public erosion control calculator.

La construction d’un ouvrage hydraulique commence par le choix des matériaux devant le constituer. Les sols employés pour la construction d’ouvrages hydrauliques en terre peuvent être constitués de matériaux perméables tels que les sables ou les graves ou de matériaux peu perméables tels que les argiles ou les limons. En fonction de la disponibilité des matériaux à proximité du chantier, il est alors possible d’opter pour différents types d’ouvrages (ouvrages homogènes, à noyau ou zonés). Dans tous les cas, le coût d’un ouvrage tel qu’une digue est d’autant moins élevé que les sols utilisés pour sa construction sont issus de zones proches du chantier. Lorsque des sols sont disponibles en quantité suffisante à proximité du chantier mais que leur utilisation soit risquée pour la stabilité de l’ouvrage, il peut être opportun de chercher à modifier leurs caractéristiques pour qu’ils puissent être utilisés dans les mêmes conditions de sécurité que les matériaux traditionnels. C’est autour de cette problématique que ce travail de thèse a vu le jour. En particulier, ce travail vise à étudier les améliorations apportées par un traitement à la chaux appliqué sur un sol grossier soumis à un écoulement interne afin de le stabiliser contre le phénomène de l’érosion interne. La compréhension des améliorations apportées a nécessité la mise en place d’une analyse multicritère au travers d’essais dédiées. Dans la première partie de la thèse, nous nous sommes employés à développer un dispositif d’essais permettant de réaliser des essais d’érosion interne sur ce type de sol. Ce dispositif nous a permis de réaliser une étude phénoménologique sur le comportement du sol considéré, soumis à des écoulements, en fonction du sens de l’écoulement et de l’application ou pas du traitement. Par la suite une étude paramétrique a été réalisée afin de mettre en évidence l’influence des paramètres principaux : dosage de traitement, temps de cure, hauteur de l’éprouvette et surcharge. Dans une seconde partie, nous nous sommes intéressés à l’influence de l’immersion des échantillons dans l’eau sur leur stabilité. A cet effet, l’essai de dispersion, adapté à ce type de sol, a pu être utilisé et exploité. Des essais complémentaires de résistance à la compression simple ont été réalisés afin d’estimer la perte de résistance après immersion. Ce qui nous a poussés à examiner l’existence de corrélations entre les propriétés à l’érosion et les propriétés mécaniques du sol traité / The construction of a hydraulic structure starts with the selection of the materials that will constitute it. The soils used in the construction of hydraulic earthen structures may be made of permeable materials such as sands or low permeability materials such as clay or silt. Depending on the availability of materials near the site, it is possible to choose different types of structures (homogeneous structures, core or zoned). In all cases, the cost of such a structure as a dike is even lower than the soils used for its construction come from areas near the site. When soils are sufficiently available near the construction site, but their use is risky for the stability of the structure, it may be appropriate to seek to modify their characteristics so they can be used in the same security conditions than traditional materials. It is around this issue that this thesis was born. More particularly, this research aims to study the improvements made by a lime treatment on a coarse soil subjected to internal flow to stabilize against the phenomenon of internal erosion. Understanding improvements requires the establishment of a multi-criteria analysis through dedicated tests. In the first part, we are interested in developing a testing device for performing internal erosion tests on this type of soil. This device has enabled us to realize a phenomenological study of the phenomena observed with the direction of flow and the presence or not of the treatment. Subsequently a parametric study was conducted to highlight the influence of the main parameters: treatment dosage, treatment time, height of the specimen and overload. In the second part, we studied the influence of immersion samples in water for this purpose the crumb test test was adapted for this type of soil. Additional unconfined compression tests were conducted to estimate the loss of strength after immersion. This allowed us to try couplings between the properties to erosion and soil treated mechanical properties

This study focuses on quantifying explicitly the sediment budget of deeply incised ravines in the lower Le Sueur River watershed, in southern Minnesota. High-rate-gully-erosion equations along with the Universal Soil Loss Equation (USLE) were implemented in a numerical modeling approach that is based on a time-integration of the sediment balance equations. The model estimates the rates of ravine width and depth change and the amount of sediment periodically flushing from the ravines. Components of the sediment budget of the ravines were simulated with the model and results suggest that the ravine walls are the major sediment source in the ravines. A sensitivity analysis revealed that the erodibility coefficients of the gully bed and wall, the local slope angle and the Manning’s coefficient are the key parameters controlling the rate of sediment production. Recommendations to guide further monitoring efforts in the watershed and increased detail modeling approaches are highlighted as a result of this modeling effort.

In the United States, the annual cost of on-site soil erosion problems such as soil and nutrient losses, and off-site soil erosion problems such as sedimentation of lakes and river, loss of navigable waterways, flooding and water quality impairment, has been estimated at 44 billion USD (Pimentel, 1995; Telles, 2011). While eroding sediment sources can either be from land or from stream/river systems, the erosion from streambanks can be quite significant, reaching up to 80% of sediment leaving a watershed (Simon et al 2002; Simon and Rinaldi 2006). Despite many decades of research one the erosion of cohesive soils by flowing water (fluvial erosion), this significant aspect of environmental sustainability and engineering is still poorly understood. While past studies have given invaluable insight into fluvial erosion, this process is still poorly understood. Therefore, the objective of this dissertation was to examine the relationship between time and erosion resistance of remolded cohesive soils, and to quantify and model the effects soil and water temperature on the fluvial erosion of cohesive soils First, erosion tests were performed to investigate how soil erosion resistance develops over time using three natural soils and testing in a laboratory water channel. Results showed that the erosion rate of the soils decreased significantly over the time since the soils were wetted. This study indicates researchers need to report their sample preparation methods in detail, including the time between sample wetting and sample testing. Second, erosion tests were performed at multiple soil and water temperatures. Results showed that increases in water temperature led to increased erosion rates while increases in soil temperature resulted in decreased erosion rate. When soil and water temperatures were equal, erosion results were not significantly different. Results also showed a linear relationship between erosion rate and the difference between soil and water temperatures, indicating erosion resistance decreased as heat energy was added to the soil. Lastly, two common erosion models (the excess shear stress and the Wilson models) were evaluated, and were modified to account for soil and water temperature effects. Results showed that, compared to the original models, the modified models were better in predicting erosion rates. However, significant error between model predictions and measured erosion rates still existed. Overall, these results improve the current state of knowledge of how erosion resistance of remolded cohesive soils evolves with time, showing the importance of this factor in the design of cohesive erosion experiments. Also, the results show that by accounting for thermal effects on erosion rate, the usability of erosion models can be improved in their use for erosion predictions in soil and water conservation and engineering practice. / PHD / In the United States, the annual cost of on-site soil erosion problems such as soil and nutrient losses, and off-site soil erosion problems such as sedimentation of lakes and river, loss of navigable waterways, flooding and water quality impairment, has been estimated at 44 billion USD (Pimentel, 1995; Telles, 2011). While eroding sediment sources can either be from land or from stream/river systems, the erosion from streambanks can be quite significant, reaching up to 80% of sediment leaving a watershed (Simon et al 2002; Simon and Rinaldi 2006). Despite many decades of research one the erosion of cohesive soils by flowing water (fluvial erosion), this significant aspect of environmental sustainability and engineering is still poorly understood. While past studies have given invaluable insight into fluvial erosion, this process is still poorly understood. Therefore, the objective of this dissertation was to examine the relationship between time and erosion resistance of remolded cohesive soils, and to quantify and model the effects soil and water temperature on the fluvial erosion of cohesive soils First, erosion tests were performed to investigate how soil erosion resistance develops over time using three natural soils and testing in a laboratory water channel. Results showed that the erosion rate of the soils decreased significantly over the time since the soils were wetted. This study indicates researchers need to report their sample preparation methods in detail, including the time between sample wetting and sample testing. Second, erosion tests were performed at multiple soil and water temperatures. Results showed that increases in water temperature led to increased erosion rates while increases in soil vi temperature resulted in decreased erosion rate. When soil and water temperatures were equal, erosion results were not significantly different. Results also showed a linear relationship between erosion rate and the difference between soil and water temperatures, indicating erosion resistance decreased as heat energy was added to the soil. Lastly, two common erosion models (the excess shear stress and the Wilson models) were evaluated, and were modified to account for soil and water temperature effects. Results showed that, compared to the original models, the modified models were better in predicting erosion rates. However, significant error between model predictions and measured erosion rates still existed. Overall, these results improve the current state of knowledge of how erosion resistance of remolded cohesive soils evolves with time, showing the importance of this factor in the design of cohesive erosion experiments. Also, the results show that by accounting for thermal effects on erosion rate, the usability of erosion models can be improved in their use for erosion predictions in soil and water conservation and engineering practice.

Les mécanismes d'érosion sont la principale cause de rupture des ouvrages hydrauliques en remblai, c'est pourquoi il est capital de pouvoir quantifier la résistance des sols à l'érosion. Divers appareillages permettent d'en obtenir une estimation, notamment le Jet Erosion Test (JET) dont le modèle d'interprétation est empirique. L'objectif de ce travail est de statuer sur la pertinence ce modèle d'interprétation. Pour cela, nous avons développé un modèle numérique 2D de type Navier-Stokes turbulent avec déplacement d'interface et remaillage, permettant de modéliser l'érosion d'un sol cohésif par un écoulement turbulent. En injectant dans notre modèle les paramètres d'érosion trouvés à la suite d'essais de JET, on retrouve numériquement l'évolution de la profondeur d'affouillement obtenue expérimentalement. Nous avons appliqué cette méthode à trois différents essais de JET, les résultats obtenus sont en bon accord avec les résultats expérimentaux. En plus d'une importante étude paramétrique, ces résultats ont permis d'apporter d'importants éléments de validation au modèle d'interprétation du JET. Pour étendre le champ d'applicabilité du modèle, nous avons également appliqué cette méthode de modélisation à la configuration de l'érosion de conduit. Trois essais de Hole Erosion Test (HET) ont été modélisés et nous avons également obtenus des résultats en bon accord avec les résultats expérimentaux. Une analyse de la loi d'érosion et des paramètres d'érosion obtenus à la suite d'essais de JET et de HET a ensuite été initiée. Les bases d'une étude portant sur l'influence de l'angle d'incidence de l'écoulement, sur l'efficacité de l'érosion, ont été posées. / Erosion mechanisms are the main cause of hydraulic failure in embankments. Therefore, the resistance of soils to erosion must be quantified. To this hand, several devices are used such as the Jet Erosion Test (JET), whose model of interpretation is strongly empirical. The aim of this study is to determine the relevance of the interpretation model of the JET. For this purpose, a 2D Navier-Stokes numerical model of erosion of cohesive soils by a turbulent flow has been proposed. We first developed and implemented an interface movement model, whose input parameters are the erosion parameters found experimentally by JET test. Then, the scour depth evolutions obtained numerically for three JET test cases are compared to experimental data. Good agreement is obtained. A parametric study has also been conducted to validate the accuracy of the numerical results. These results contribute to the validation of the JET interpretation model. To extend its domain of application, we applied the numerical model to concentrated leak erosion during Hole Erosion Tests (HET). Three HET were modeled and, here again, our numerical results are in satisfactory agreement with the experimental results from the tests. An analysis of the erosion law and erosion parameters obtained with JET and HET was finally initiated. The potential influence of the flow incidence angle on the erosion efficiency was underlined.