Island Surface Area Research Articles

Influence of precipitation event magnitude on baseflow and coastal nitrate export for Prince Edward Island, Canada

AbstractThe export of anthropogenic nitrate to coastal waters, which depends on the interplay between many factors such as land use and meteorological forcing, is a rising concern in many regions of the world. The present study investigates the effect of precipitation event magnitude on baseflow and associated groundwater‐driven nitrate export in Prince Edward Island, Canada. Twenty‐year time‐series of precipitation, stream flow, and groundwater levels across the island were analysed to establish a three‐way relationship between precipitation, groundwater level rise, and baseflow increase along a hydrological response pathway in this island setting. The analysis was performed by extracting hydrological responses for groundwater level and baseflow for a selected subset of relatively isolated precipitation events. The results reveal a non‐linear relationship between precipitation event magnitude and baseflow change that is also observed for precipitation events associated with hurricanes and post tropical storms. A time‐series of streamflow nitrate concentrations during Hurricane Dorian's passage (September 2019) was used to evaluate the relevance of these findings for nitrate export. The data show that baseflow increases after a heavy precipitation event have limited impact on streamflow concentrations, but result in substantial and sustained increase of nitrate export (calculated by multiplying concentration by flow). These observations are consistent with a recharge‐induced water table rise leading to increased hydraulic gradients that drive discharge of shallow nitrate‐containing groundwater. Due to the similarity of the processes governing groundwater flow to the sea and to streams, the results can be used to gain insights into the impacts of precipitation event magnitude on direct groundwater discharge to coastal waters. On Prince Edward Island, this applies to at least the 13% of the island's surface area that is closer to the ocean than to any stream and likely feeds submarine groundwater discharge pathways.

Evaluating the state-of-the-art in remote volcanic eruption characterization Part I: Raikoke volcano, Kuril Islands

Raikoke, a small, unmonitored volcano in the Kuril Islands, erupted in June 2019. We integrate data from satellites (including Sentinel-2, TROPOMI, MODIS, Himawari-8), the International Monitoring System (IMS) infrasound network, and global lightning detection network (GLD360) with information from local authorities and social media to retrospectively characterize the eruptive sequence and improve understanding of the pre-, syn- and post- eruptive behavior. We observe six infrasound pulses beginning on 21 June at 17:49:55 UTC as well as the main Plinian phase on 21 June at 22:29 UTC. Each pulse is tracked in space and time using lightning and satellite imagery as the plumes drift eastward. Post-eruption visible satellite imagery shows expansion of the island's surface area, an increase in crater size, and a possibly-linked algal bloom south of the island. We use thermal satellite imagery and plume modeling to estimate plume height at 10–12 km asl and 1.5–2 × 106 kg/s mass eruption rate. Remote infrasound data provide insight into syn-eruptive changes in eruption intensity. Our analysis illustrates the value of interdisciplinary analyses of remote data to illuminate eruptive processes. However, our inability to identify deformation, pre-eruptive outgassing, and thermal signals, which may reflect the relatively short duration (~12 h) of the eruption and minimal land area around the volcano and/or the character of closed-system eruptions, highlights current limitations in the application of remote sensing for eruption detection and characterization.

An equilibrium theory signature in the island biogeography of human parasites and pathogens

AbstractAimOur understanding of the ecology and biogeography of microbes, including those that cause human disease, lags behind that for larger species. Despite recent focus on the geographical distribution of viruses and bacteria, the overall environmental distribution of human pathogens and parasites on Earth remains incompletely understood. As islands have long inspired basic ecological insights, we aimed to assess whether the microorganisms that cause human disease in modern times follow patterns common to insular plants and animals.LocationGlobal and regional.MethodsRelying on the publically accessible GIDEON database, we use the spatial distribution of nearly 300 human parasites and pathogens across 66 island countries and territories to assess the current predictive value of the ‘equilibrium theory’ of island biogeography. The relationships between species richness and (1) island surface area and (2) distance to the nearest mainland were investigated with linear regression, and ANCOVAs were used to test for differences in these relationships with respect to pathogen ecology and taxonomy.ResultsPathogen species richness increases with island surface area and decreases with distance to the nearest mainland. The effect of area is more than 10 times lower than that usually reported for macroorganisms, but is greater than the effect of distance. The strongest relationships are for pathogens that are vector‐borne, zoonotic (with humans as dead‐end hosts) or protozoan.Main conclusionOur results support the basic predictions of the theory: disease diversity is a positive function of island area and a negative function of island isolation. However, differences in the effects of area, distance and pathogen ecology suggest that globalization, probably through human travel and the animal trade, has softened these relationships. Parasites that primarily target non‐human species, whose distributions are more constrained by island life than are those restricted to human hosts, drive the island biogeography of human disease.

Flora and factors affecting species diversity in protected “Natura 2000” sites of the Ionian area: the Echinades islet group (Greece)

Iliadou E., Panitsa M., Raus Th. & Dimopoulos P.: Flora and factors affecting species diversity in protected “Natura 2000” sites of the Ionian area: the Echinades islet group (Greece). — Willdenowia 44: 121–136. 20 March 2014. — Version of record published online ahead of inclusion in April 2014 issue; ISSN 1868-6397; © 2014 BGBM Berlin-Dahlem.DOI: http//dx.doi.org/10.3372/wi.44.44113The vascular plant species diversity of the Echinades islet group, quite unexplored so far, is documented by an inventory of flowering plants and ferns, filling a gap in the floristic information available for the National Park to which these islets belong, as well as for the Ionian land-bridge island system, for which detailed studies concerning floristic and phytogeographical relationships were available before. Field investigations on 19 of the 20 Echinades islets generated an inventory of plant species composition for the first time for 18 of them and added 56 taxa as new to the islet of Oxeia as compared to previous literature. The total vascular flora of the Echinades islets comprises 386 plant taxa. Spectra of life-form and chorological categories are presented and discussed. Floristic cross-correlations (beta-diversity) showed that the individual islet floras differ from each other from 25 % to 85 %. Concerning the role of geographical variables as influencing plant species diversity in the area, regression analyses indicated island surface area and elevation as the major predictor variables of species richness, while distance to the mainland plays a subordinate predictive role.

Evaluation of the levels of alcohol sulfates and ethoxysulfates in marine sediments near wastewater discharge points along the coast of Tenerife Island

Alcohol sulfates (AS) and alcohol ethoxysulfates (AES) are all High Production Volume and ‘down-the-drain’ chemicals used globally in detergent and personal care products, resulting in low levels ultimately released to the environment via wastewater treatment plant effluents. They have a strong affinity for sorption to sediments. Almost 50% of Tenerife Island surface area is environmentally protected. Therefore, determination of concentration levels of AS/AES in marine sediments near wastewater discharge points along the coast of the Island is of interest. These data were obtained after pressurized liquid extraction and liquid chromatography–tandem mass spectrometry analysis. Short chains of AES and especially of AS dominated the homologue distribution for AES. The Principal Components Analysis was used. The results showed that the sources of AS and AES were the same and that both compounds exhibit similar behavior. Three different patterns in the distribution for homologues and ethoxymers were found.

Multidecadal Atoll Shoreline Change on Manihi and Manuae, French Polynesia

Yates, M.L.; Le Cozannet, G.; Garcin, M.; Salai, E., and Walker, P., 2013. Multidecadal atoll shoreline change on Manihi and Manuae, French Polynesia.As interest in the impact of sea-level rise on atoll islands increases, this study contributes to the growing database of observations of shoreline changes on South Pacific Islands, where few observations are currently available. Historical aerial photographs and recent satellite images were used to evaluate multidecadal surface area and shoreline changes on two atolls in French Polynesia: Manihi and Manuae. During the 40- to 50-year study period, atoll island surface area primarily increased or remained stable on Manihi and decreased on Manuae. Distinct ocean and lagoon shoreline changes were observed in different geographical regions of each atoll. On Manihi, ocean shoreline accretion rates were larger on the NW rim than the SE rim. On Manuae, atoll islands on the NE rim were eroding on the lagoon side and accreting on the ocean side, whereas islands on the SE rim showed the opposite trend. Sea-level rise is often thought to cause atoll erosion, but in this study, lagoon and ocean shorelines both eroded and accreted over a period when sea-level rise rates were greater than the global mean. Surface area changes related directly to anthropogenic activities were identified on only two of the 47 atoll islands. After completing a classification of the incident wave field, it was hypothesized that waves have an important role in controlling the shoreline change variability. Additional field surveys and in situ observations are needed to validate this hypothesis and to understand better island response to changing forcing factors.Une analyse de la mobilité du trait de côte au cours des cinquantaines dernières années a été réalisée sur deux atolls de Polynésie Franaise (Pacifique Sud): Manihi (Nord-ouest de l'archipel des Tuamotus) et Manuae (Est de l'archipel des îles de la Société). La mobilité de la limite de végétation permanente a été extraite de photographies aériennes anciennes de 1955 ou 1961 et d'images satellites à haute résolution acquises dans les années 2000. Cette analyse a nécessité le géoréférencement des photographies aériennes puis la digitalisation des limites successives de la végétation permanente. La ligne de végétation permanente a été utilisée comme marqueur des mouvements de basse fréquence du trait de côte (i.e., échelles de temps pluri-décennales). En effet, elle demeure aisément identifiable aussi bien sur les images anciennes que récentes tout en s'émancipant des variations à haute fréquence (marée, surcote etc.) et des difficultés de pointage de certains marqueurs sur les photographies anciennes. Les incertitudes liées au géoréférencement et à la digitalisation du trait de côte ont été évaluées et conduisent à ne considérer que des mouvements supérieurs à 5m sur la durée considérée. Dans de trés nombreux îlots (motu), des changements de plus grande ampleur sont observés et sont de fait sont considérés comme significatifs. Ils indiquent une tendance générale à l'érosion à Manuae et à l'accrétion à Manihi. Cependant, au sein d'un même atoll, nous observons une grande variabilité des évolutions des limites de végétation des motu : ainsi, la plupart des motu sont en accrétion côté lagon et côté océan à Manihi, toutefois, certains sont en érosion côté océan, côté lagon ou bien des deux côtés. Dans ces deux atolls peu anthropisés, les aménagements ne modifient la ligne de rivage que dans deux des 47 motu étudiés (quarante-et-un à Manihi, six à Manuae). Selon Becker et al. (2012), l'élévation du niveau marin, dans cette partie du Pacifique, a été supérieure à la moyenne globale depuis 60 ans. Des études antérieures suggèrent que l'élévation du niveau marin induit une érosion des îlots notamment sur leur face océanique. Ces effets n'apparaissent pas dominants dans les deux atolls étudiés. Au contraire, la tendance d'évolution du trait de côte obsevée n'est pas hom

ECOLOGICAL FIDELITY OF PLEISTOCENE-HOLOCENE LAND SNAIL SHELL ASSEMBLAGES PRESERVED IN CARBONATE-RICH PALEOSOLS

Studies that assess the ecological fidelity—preservation of the original community—of terrestrial shell accumulations are uncommon but essential to infer accurate changes in past ecosystems. When live-dead comparisons are unavailable, the taxonomic agreement between differing taphofacies may be used to evaluate the fidelity of ancient shelly assemblages. This approach was used to approximate the fidelity of Quaternary land snails preserved in carbonate-rich paleosols from the northeastern islets of the Canary Archipelago. Such macroscopic alteration as fragmentation, corrosion, carbonate coating, and color loss affected shells, however, microscopic analyses concluded substantial diagenetic alterations unlikely. The shell abundance negatively correlated with fragmentation, suggesting that a higher proportion of shells may be a consequence of higher shell input rate and lower shell destruction rate rather than lower sedimentation rate, as predicted by taphonomic models. Strongly and weakly altered taphofacies significantly differed in species abundances. Substantial taphonomic bias was improbable, however, because both taphofacies contained taxa with comparable durability. Temporal fluctuations in taphonomy and ecology suggest variable environmental conditions operated through time. The overall decline in shell abundance from the last glacial to interglacial paleosols may be explained by a decline in humidity and reduced island surface area resulting in lowered snail proliferation, and in turn, a decreased net shell input rate. This study emphasizes that the original community is preserved within the studied terrestrial shell accumulations regardless of the degree of taphonomic alteration. Measures of past taxonomic richness and diversity, therefore, may be used as a reliable measure of the original snail community.

Water Currents and Water Budget in a Coastal Megastructure, Palm Jumeirah Lagoon, Dubai, UAE

Abstract Palm Jumeirah is the most completely developed of several man-made coastal island megaconstructions in Dubai, United Arab Emirates. The palm-shaped island, surrounded by an elliptical breakwater, was developed 7 y ago, has an overall footprint of 23 km2, of which the constructed island surface area is 7.9 km2, and is connected to shore via a 5-km-long spine from the mainland to the crescent tip. Time-series observations of hydrographic variables and currents within the interior of the development (Palm Jumeirah Lagoon) during 30 d in April–May 2008 were utilized to examine current flow, tide variability, water budget, vertical mixing, and turnover time within this megastructure. Currents within Palm Jumeirah Lagoon varied between stations; however, similar water temperatures and salinities were apparent throughout all the stations. Palm Jumeirah Lagoon tides were mixed and mainly semidiurnal, with spring and neap tidal ranges measuring 116 and 56 cm, respectively, and no difference in amplitude o...

Biological geography of the European seas: results from the MacroBen database

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 382:265-278 (2009) - DOI: https://doi.org/10.3354/meps07955 Contribution to the Theme Section ‘Large-scale studies of the European benthos’ Biological geography of the European seas: results from the MacroBen database C. Arvanitidis1,*, P. J. Somerfield, H. Rumohr, S. Faulwetter, V. Valavanis, A. Vasileiadou, G. Chatzigeorgiou, E. Vanden Berghe, J. Vanaverbeke, C. Labrune, A. Grémare, M. L. Zettler, M. Kedra, M. Wlodarska-Kowalczuk, I. F. Aleffi, J. M. Amouroux, N. Anisimova, G. Bachelet, M. Büntzow, S. J. Cochrane, M. J. Costello, J. Craeymeersch, S. Dahle, S. Degraer, S. Denisenko, C. Dounas, G. Duineveld, C. Emblow, V. Escavarage, M. C. Fabri, D. Fleischer, J. S. Gray, C. H. R. Heip, M. Herrmann, H. Hummel, U. Janas, I. Karakassis, M. A. Kendall, P. Kingston, L. Kotwicki, J. Laudien, A. S. Y. Mackie, E. L. Nevrova, A. Occhipinti-Ambrogi, P. G. Oliver, F. Olsgard, R. Palerud, A. Petrov, E. Rachor, N. K. Revkov, A. Rose, R. Sardá, W. C. H. Sistermans, J. Speybroeck, G. Van Hoey, M. Vincx, P. Whomersley, W. Willems, A. Zenetos 1Institute of Marine Biology and Genetics, and Institute of Marine Biological Resources, Hellenic Centre for Marine Research, PO Box 2214, Heraklion 71003, GreeceAddresses for all authors are given in the Electronic Appendix at www.int-res.com/articles/suppl/m382p221_app.pdf *Email: arvanitidis@her.hcmr.gr ABSTRACT: This study examines whether or not biogeographical and/or managerial divisions across the European seas can be validated using soft-bottom macrobenthic community data. The faunal groups used were: all macrobenthos groups, polychaetes, molluscs, crustaceans, echinoderms, sipunculans and the last 5 groups combined. In order to test the discriminating power of these groups, 3 criteria were used: (1) proximity, which refers to the expected closer faunal resemblance of adjacent areas relative to more distant ones; (2) randomness, which in the present context is a measure of the degree to which the inventories of the various sectors, provinces or regions may in each case be considered as a random sample of the inventory of the next largest province or region in a hierarchy of geographic scales; and (3) differentiation, which provides a measure of the uniqueness of the pattern. Results show that only polychaetes fulfill all 3 criteria and that the only marine biogeographic system supported by the analyses is the one proposed by Longhurst (1998). Energy fluxes and other interactions between the planktonic and benthic domains, acting over evolutionary time scales, can be associated with the multivariate pattern derived from the macrobenthos datasets. Third-stage multidimensional scaling ordination reveals that polychaetes produce a unique pattern when all systems are under consideration. Average island distance from the nearest coast, number of islands and the island surface area were the geographic variables best correlated with the community patterns produced by polychaetes. Biogeographic patterns suggest a vicariance model dominating over the founder-dispersal model except for the semi-closed regional seas, where a model substantially modified from the second option could be supported. KEY WORDS: Marine biodiversity · Biogeography · Macrobenthos · Polychaetes · Europe Full text in pdf format PreviousNextCite this article as: Arvanitidis C, Somerfield PJ, Rumohr H, Faulwetter S and others (2009) Biological geography of the European seas: results from the MacroBen database. Mar Ecol Prog Ser 382:265-278. https://doi.org/10.3354/meps07955Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 382. Online publication date: April 30, 2009 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2009 Inter-Research.

Scaling tidal channel geometry with marsh island area: A tool for habitat restoration, linked to channel formation process

Hydraulic geometry and related analyses are often used to investigate tidal channel geometry and evolution and inform marsh restoration. An alternative approach is presented that avoids calculating tidal prism and allows analysis of additional channel metrics. It relies on scaling relationships between marsh island surface area and various metrics of the set of tidal channels draining each island. In the Skagit Delta marshes (Washington, United States), total channel surface area and length and surface area of the largest channel draining an island scaled disproportionately with island area, suggesting restoration of a 100‐ha site would be preferable to restoration of 10 separate 10‐ha sites to maximize channel length and area. A model of channel formation through random island conglomeration replicated observed scaling patterns, linking channel scaling to blind channel evolution from river distributaries. Channel size and complexity varied spatially, with significant deficits in an eroding marsh isolated from river distributaries and riverine sediments.

Aerial dispersal of springtails on the Antarctic Peninsula: implications for local distribution and demography

Aerial dispersal has been frequently proposed as a potential mechanism by which polar terrestrial arthropods are transported to, and settle the ice free habitats of Antarctica, but to date there has been little substantive evidence in support of this hypothesis. Using water traps we investigated aerial deposition of arthropods on Lagoon Island, Ryder Bay, on the Antarctic Peninsula. Over a period of five weeks, trapping at three different altitudes, we captured a total of nine springtails, Cryptopygus antarcticus, all alive. This is the first study to demonstrate conclusively the survival of wind-borne native arthropods within Antarctica. By scaling the modest trapping area and success against island surface area, it is clear that hundreds, if not thousands, of springtails are regularly relocated by winds between the terrestrial habitats of Marguerite Bay. We use known desiccation rates of C. antarcticus and wind speeds to predict the likelihood of successful dispersal between the principal terrestrial habitats of the larger Marguerite Bay. Implications for local and long-range dispersal are discussed in relation to C. antarcticus and other polar arthropods.

Species diversity and endemism of five major Malesian islands: diversity–area relationships

AbstractAim A comparison of biodiversity patterns within Malesia in relation to surface area.Location Analysis of the patterns in species richness and endemism of vascular plants in the five major Malesian islands, i.e. Java, Sulawesi, Sumatra, Borneo and New Guinea.Methods Available data on species richness and species ranges in correlation with the surface area of the respective islands were examined in this work. Estimations of total species numbers for these islands are presented based on extrapolation of all available published Flora Malesiana information and recent checklists, all in all comprising 12,000 different species. The regression analysis of overall species richness and endemism were studied for all species together as well as for different plant families to compare the fit with the Arrhenius species–area model.Results The five islands form a series of independent areas of increasing size suited for an analysis of the species–area relationships at the regional scale. All species taken together and those of families with even distribution throughout Malesia show significant species–area relationships. Non‐significant relationships were detected in families with western or eastern‐centred Malesian distribution patterns. Relationships between number of endemic species and surface area are significant for all species and for the majority of the families with significant species–area relationships.Main conclusions Species–area relationships of families appear to be dependent on species number. Families with high numbers of species usually have a significant species–area relationship whereas small families have not. For the families that display an eastern or western Malesian centred pattern, a historical biogeographical explanation should be invoked. Island surface area appears to be a predictor for island percent endemism in Malesian vascular plants. None of the islands appears to be a hotspot of endemism nor of species diversity, as no significant departure from the Arrhenius model was noted for any of them.

Natural Disturbances and Mining of Panamanian Coral Reefs by Indigenous People

Abstract: Before the 1980s, coral reefs were considered relatively stable and healthy in Kuna‐Yala, Caribbean Panama. During the 1980s, however, several natural disturbances changed the reef's community structure. We evaluated historical changes in coral cover and for the first time provide quantitative evidence of a large‐scale process of reef degradation. This process started long before the onset of these disturbances as a result of demographic growth and the traditional practices of the Kuna people. Living coral cover declined 79% in 30 years ( 1970–2001 ) while the indigenous population increased 62%. We measured 20 km of seawall built with mined reef corals ( 16,000 m 3 ) and an increase in island surface area of 6.23 ha caused by coral land filling. Consequently, coastal erosion has increased as a result of the lack of a protective natural barrier and a 2.0 cm/year local increase in sea level. Coral‐mining and land‐filling practices to accommodate population expansion and mismanagement of resources have significantly modified the reef ecosystem and will have serious long‐term consequences. We propose eight priority conservation areas within the Indian reserve, based on reef conservation status. The Kuna people and their leaders are considering a cultural change, which may include a gradual and organized migration to the mainland, and have optimistically accepted our results.

Nest-density distribution patterns in a yellow-legged gull archipelago colony

Abstract The nest density distribution of yellow-legged gulls Larus cachinnans was investigated on the large Marseille archipelago colony (south-east France) which houses c. 18 000 breeding pairs. The study was performed at two investigation scales, including both mean nesting density on the nine study islands and density distribution within 171 sampling plots. The mean nesting density on each island was negatively correlated with island surface area and with the distance from the initial colony location (south-east end of the archipelago). No significant correlation was found with the other island parameters analysed (maximum elevation, shape index and distance from continent). A partial least squares regression performed between denstiy data from 171 500 m 2 sampling plots and environmental variables showed that the mostly explaining factors were island isolation and percentage of rocks in the plots (positive correlation), and distance of the island from the south-east end of the archipelago, island area, distance from plot to seaside and percentage of stone in the plots (negative correlation). Thus in our case, vegetation parameters (cover and height) were not influencial factors in nest density distribution.

Histoire de l'invasion d'une plante introduite, Miconia calvescens, dans une île polynésienne, Tahiti

Miconia calvescens DC (Melastomataceae), a forest understory shrub native of central America was introduced into Tahiti in 1937 due to its ornemental attributes. For about thirty years, it was found near gardens, in secondary forests or as a primary forest understory shrub. Ever since, it's distribution extends from the lowland up to the midland wet forests, bringing about the extinction of several endemic species. It occupies 75 % of the island's surface area, most parts of Moorea island, and is fast spreading on other islands of the Society archipelago. Hazardously dispersed, it starts off by penetrating Tahitian forests which are marked by the small height of their emergent trees. It then gradually reaches the forest cover, outgrows the emergents and makes up a monospecific canopy which now dictates new understory microclimatic conditions incompatible with the ecological requirements of indigenous species. Considering several parameters, some which are intrinsic to the island's ecosystem and others to climatic conditions or to species biology, this paper demonstrates that the fragility of an island's ecosystem towards allochton plants is related not only to fundamental parameters such as forest structure and reproduction biology but is also dependant on hazardous events such as climatic perturbation or the involuntary introduction of a bird...

Hydrology, hydraulics, and geomorphology of the Upper Mississippi River system

The Upper Mississippi River system has been modified with locks, dams, dikes, bank revetments, channel modifications, and dredging to provide a nine-foot navigation channel. These activities have changed the river's characteristics. The historical changes in the hydrologic, hydraulic, and geomorphic characteristics were assessed and related to navigational development and maintenance activities in the Upper Mississippi River system. The hydrologic, hydraulic, and geomorphic features studied include river discharges, stages, sediment transport, river position, river surface area, island surface area, and river bed elevation. Water and sediment transport effects on dredging were also estimated. It was found that the general position of the Upper Mississippi River system has remained essentially unchanged in the last 150 years except for specific man-made developments in the river basin. The stage, velocity, sediment transport, and river and island areas were altered by development of the 2.75-m navigation system. Dredging requirements are strongly related to mean annual water discharge. Years in which water discharges were great were generally the years during which large volumes of sediment needed to be dredged from the channel. The backwater areas are experiencing some deposition. With implementation of erosion-control measures in major tributaries and upland areas, better confinement of disposed dredged materials, and better maintenance practices, the sedimentation and pertinent problems in the main channel, as well as in the backwater areas, may be reduced with time.

Geomorphic Study of Upper Mississippi River

In order to estimate the effects of removal of snags hazardous to navigation and construction of dikes, revetment, and locks and dams on the river geomorphology, the past and present geomorphic features of the Upper Mississippi River were studied. The geomorphic features studied include: the river position, river surface area, island surface area, number of islands, riverbed surface area, surface widths, water depth, side channels, and riverbed elevations. The study results indicate that natural and man-induced activities in the last 150 yr have produced subtle changes in the river geomorphology. The low dike fields narrowed the river, created new islands and chutes, and enlarged old islands. Locks and dams have widened the river and increased the number of islands in the pools. It was concluded that 50 yr from now the river scene of the Upper Mississippi River will be essentially as it is today if no major man-made changes or natural events occur.