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Salt marshes provide important habitats for many species in the estuaries along the east and Gulf coasts of North America. With many species dependent on these coastal marshlands and extensive documentation that these marshlands are disappearing, a clear understanding of the mechanisms causing loss is critical. Much of the salt marsh was lost to reclamation and construction before these activities were curtailed circa 1970; however, losses due to other causes have continued and multiple hypothesized causes have been proposed, not all mutually exclusive. Yet it remains unclear whether there are legacy effects from the reclamation projects. When the edges of salt marshes are cut into, and gentle vegetated slopes are replaced by sharp edges adjoining deep water of 2 m or more, erosion could accelerate and could continue for many years. One method that may help shed light on the relative importance of the various causes of salt marsh erosion would be to compare the erosion rates of specific edges within a marshland that are exposed to particular conditions. We therefore used several sets of aerial photography spanning 84 years to track the changes at specific edge locations along marsh edges and then make comparisons between anthropogenically created edges and naturally created edges, including comparisons within use and width categories of navigational channels. Erosion rates were found to remain significantly higher on channelized edges than along other-wise similar wetland edges even several decades after modification. Likely reasons include the continued exposure of underlying layers that lack reinforcing plant root systems, vertical edges that are more vulnerable to undermining from wave action, and increased erosion related to altered tidal flows.

Field studies and aerial photograph interpretation suggest that large sections of Jamaica Bay salt marshes in New York City near John F. Kennedy International Airport are deteriorating rapidly. The relatively recent salt marsh losses may be caused by a variety of factors, potentially interacting synergistically. Possible factors include reduced sediment input, dredging for navigation channels, boat traffic, and regional sea-level rise. Field work included aboveground biomass measurements of Spartina alterniflora, mapping plant community distribution, and documenting biogeomorphological indicators of marsh loss. Current productivity (standing crop biomass), which ranged from approximately 700 to 1500 g m−2, was typical of healthy marshes in this region, in spite of other indicators of marsh degradation. Historical aerial photographs of several islands showed that sampled marshes have diminished in size by ∼12% since 1959. Overall island low marsh vegetation losses since 1974 averaged 38%, with smaller islands losing up to 78% of their vegetation cover. Ground observations indicate that major mechanisms of marsh loss include increased ponding within marsh interiors, slumping along marsh edges, and widening of tidal inlets. Projections of future sea-level rise, using outputs from several global climate models and data from local tide gauges, in conjunction with a range of plausible accretion rates, suggest that under current stresses, Jamaica Bay salt marshes are unlikely to keep pace with accelerated rates of sea-level rise in the future.

Geochemical analysis of 210 Pb-dated sediment cores from Otisco Lake (New York) combined with analysis of recent land cover change in the watershed revealed the history of land use change, lake management, and industrial pollution since European settlement in the northeastern US. Clearance of forestland for agriculture characterized the early settlement era that was marked in the Otisco Lake sediments by a decline in organic carbon (OC) and OC:N ratios, which indicate a change in the sources of organic matter to the lake. Agricultural land use reached its greatest areal extent in the Otisco watershed around 1900, followed by field abandonment and reforestation over the last century. In the 1920s sediment accumulation rates began to increase coincident with residential development along the lake shore. Nitrogen and organic carbon, which are transported from the watershed, show increased fluxes to the lake in response to this change. Deposition of inorganic carbon increased markedly over a short period from the 1940s to the 1980s, which is consistent with enhanced mobilization of watershed calcium by increased acidic deposition, followed by alkalinization of the lake waters and calcite precipitation. An increase in copper content in the sediments reflects application, since 1942, of the algicide copper sulfate to the lake waters to control algal blooms. This CuSO 4 marker confirmed the accuracy of the 210 Pb chronology. Atmospheric mercury (Hg) fluxes to the lake were affected by increased sediment transport from the watershed. The maximum Hg peak in the sediment record, however, was dated to the early 1970s and coincides with maximum Hg emissions to the atmosphere in the Great Lakes region.

Remote sensing is becoming a vital tool for understanding the changing vegetation patterns that are associated with broad-scale plant invasions. The establishment of North American east coast native Spartina alterniflora (smooth cordgrass) in Willapa Bay, Washington is a specific example of broad-scale invasion following local introduction. In this study, we examined a 120-y historical record of aerial photographs, oral histories, museum records, and publications to reconstruct the spatial, temporal, and historical elements of this invasion. We conclude that the most likely means for S. alterniflora to have reached Willapa Bay was the transport and translocation of oysters from New York harbour. Our data and analysis suggest that multiple areas were colonized between 1894 and 1920 coincident with sustained import of oysters from the Atlantic seaboard. We have evidence that S. alterniflora had been long established and growing in multiple widely spread locations by 1945, which is in contrast to a widely reported single introduction. Multiple foci would not only explain the colonization patterns we have observed, but could also increase the heterogeneity of the founding populations, helping to overcome barriers to reproduction that may have initially slowed the colonization in isolated populations during the first 50–70 y.

Two large groins were constructed soon after a severe erosion episode in 1962. The gross longshore transport is substantially larger than the net drift at the location. Depending on the sequence of conditions sand fillets sometimes accumulate on the east side and sometimes on the west. Over the long term the average beach is expected to be wider on the east side. The structures and associated sand deposits that have developed over the last forty years function as artificial headland. The local wave climate is altered, and in the absence of a predominant net longshore transport, a crenulate shoreline can form on both sides of the pair of structures in conformance with wave refraction and diffraction around a headland.

Remote sensing technology has been widely recognized for contributing to emergency response efforts after the World Trade Center attack on September 1 lth, 2001. The need to coordinate activities in the midst of a dense, yet relative-ly small area, made the combination of imagery and mapped data strategi cally useful. This paper reviews the role played byaerial photography, satellite imagery, and LIDAR data at Ground Zero. It examines how emergency managers utilized thesedatasets, and identifies significant problems that were encountered. It goes on to explore additional ways in which imagerycould have been used, while presenting recommend ations for more effective use in future disasters and Homeland Security applications. To plan adequately for future events, it was important to capture knowledge from individuals who responded tothe World Trade Center attack. In recognition, interviews with key emergency management and geographic information sys-tem (GIS) personnel provide the basis of this paper. Successful techniques should not be forgotten, or serious problems dismissed. Although widely used after September 11 th, it is important to recognize that with better planning, remote sensing and GIS could have played an even greater role. Together with a data acquisition timeline, an expanded discussion of these issues is available in the MCEER/NSF report \"Emergency Response in the Wake of the World Trade Center Attack: The Remote Sensing Perspective\" (Huyck and Adams, 2002).

Quantifying measurement error and precision may be the most difficult step of shoreline recession rate calculations. Calculation of long-term shoreline recession rates based on aerial photograph analysis reflect only the shoreline positions at the time of photography. Conventional methods of long-term recession rate calculation were combined with beach profiling techniques in order to quantify potential errors that can be produced by short-term variations in shoreline position. Monthly beach profiling of a typical northeastern/mid-Atlantic microtidal and wave-dominated shoreline demonstrated short-term shoreline position changes of up to 20 m over a one year period. Average long-term shoreline recession rates in this area were 1.2 m/yr 1.0 m/yr. Short-term shoreline position changes were the largest source of error in the long-term recession rate measurements. This emphasizes that photographed shorelines do not necessarily represent the seasonal mean shoreline position, particularly in locations where shorelines characteristically exhibit relatively large short-term variations in shoreline position. /// Die Quantifizierung von Mefifehlern und die Prazison der Messung sind wahrscheinlich die schwierigsten Faktoren bei der Berech-nung der Kiistenriickverlagerungsgeschwindigkeit. Die Berechnungen von Kiistenverlagerungen iiber langere Zeitraume, die auf Luftbildaufnahmen basiern, spiegelt nur die Lagezustande der Kustenlinien zur Zeit der jeweiligen Aufnahmen wider. In Ergan-zung zu den konventionellen Methoden zur Berechnung der Kiistenverlagerung werden morphometrische Karten des Strandes angefertigt um die moglichen Fehler, die durch kurzfristige Schwankungen der Kiistenlinie entstehen konnen, zu quantifizieren. Monatliche morphometrische Aufnahmen einer typischen nordosWmittelatlantischen, mikrotidalen und durch Wellen gepragten Kiistenlinie zeigte, dafi kurzzeitige Schwankungen der Kiistenlinie von bis zu 20 m in einem Jahr auftreten konnen. Die durchs-chnittliche Langzeit- Kustenverlagerungsrate betragt in diesem Gebiet l,2m/a 1,0 m/yr. Die kurzfristigen Schwankungen stel-len die hauptsachliche Fehlerquelle bei den Messungen der Langzeit-Kiistenverlagerung dar. Dies weist verstarkt darauf hin, daB Luftbildaufnahmen von Kustenlinien nicht notwendigerweise die jahreszeitliche durchschnittliche Position der Kiistenlinie reprasentieren, insbesondere an Lokalitaten, wo der Verlauf der Kiistenlinie vergleichsweise groBen Kurzzeit-Schwankungen unterworfen ist. /// L'etape la plus difficile a franchir pour estimer le recul du rivage est de quantifier les erreurs de mesure et leur precision. Les calculs de taux de recul du rivage a long terme reposent sur l'analyse de photographies aeriennes qui donnent le position du rivage instantane au moment de la prise de vue. Les méthodes conventionnelles d'estimation de recul a long terme ont ete combinees a un profilage des plages pour pouvoir quantifier les erreurs qui peuvent etre generees par les variations a court terme de la position du rivage. Le profilage mensuel d'une plage typique du NW de l'Atlantique moyen de type microtidal et doming par les houles presente une vatiation atteignant 20 m sur un an. Les taux moyens de recul dans cette zone sont de 1,2 m/an 1. Ce sont les changements a court terme qui sont les sources les plus importantes d'erreurs du calcul des taux de recul a long terme. Ceci souligne le fait que les photographies de rivages ne representent pas forcement la position moyenne saisonniere du rivage, surtout la ou d'importantes variations a court terme sont enregistrees. /// La cuantificacion del error y la precision de medida puede ser la etapa mas dificil en los calculos de la velocidad de recesion de la linea de costa. Los calculos de las velocidades de recesion a largo plazo, basados en la fotografia aerea, reflejan solo las posiciones de la linea en el instante de la fotografia. Los mStodos convencionales de calculo de la recesion a largo plazo se combinan con tecnicas de perfil de playas para cuantificar los errores potenciales que pueden producirse por las variaciones a corto plazo en la posicion de la linea de costa. El perfilado mensual de una linea de costa tipica micromareal y dominada por el oleaje en el Nordeste Atlantico demuestra que las variaciones a corto plazo en la posicion de la linea de costa pueden ser de hasta 20 m en el periodo de un ano. La velocidad media de recesibn a largo plazo con ese area es de 1.2 m/ano 1.0 m/ano. Los cambios de posicion de la linea de costa a corto plazo fueron las mayores fuentes de error en las medidas de la velocidad de recesion a largo plazo. Esta remarca que las lineas de costa fotografiadas no representan necesariamente su posicion media estacional, especialmente en aquellos lugares donde la linea de costa presenta variaciones a corto plazo relativamente importantes..

Glacial diversion of drainage has been a factor of first importance in determining the existing pattern of stream courses in regions occupied by Pleistocene continental glaciers. Aside from the well-known, large scale changes resulting from deposit of drift, transection of minor and major water partings by overflows from glacier-ponded waters was an important item in the reordering of stream courses. The efficacy of this type of crosion does not seem to have been fully appreciated. Deep gorges were evidently eroded with great rapidity by such overflow streams. In some places the cuts thus made served of themselves to confirm postglacial drainage in new channels. Elsewhere glacial erosion modified and commonly greatly enlarged the water-cut overflow channels. There is a marked tendency to compel the glacially reconstructed drainage to arcuate courses which reflect the outline of the normal lobate margins of the ice front.