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The objective of this research is to deliver an unprecedented study of hourly SWAT model simulations of discharge in two local watersheds (around 50 km2). An urbanized watershed and a forest watershed across northwest Delaware and northeastern US were selected. Both watersheds are developed and vulnerable to flash flood. Very high resolution (2 m) topography and land use information were used to depict complex urban landscape. The model calibration and validation were performed on 2010 and 2011, starting with 2009 as model spin-up period. Satisfactory fitness results were achieved at both forest and urbanized watershed, with the Nash–Sutcliff coefficients of 0.68 and 0.77, R2 of 0.7 and 0.78, and percent bias of 1.5 and 9.3, respectively. The calibration results showed that the 2-m land use accurately captured the impervious surface due to 8.9% adjustment of curve number. But, greater steepness of slope derived from 2-m DEM leads to faster runoff than reality, which means 2-m DEM does not accurately depict the topography and finer detail DEM is needed to capture the local topographic variation. To reproduce the seasonality of discharge at hourly time step, additional examination of parameters influencing baseflow was needed as part of local sensitivity test. For the peak flow dynamic simulation, substantial adjustments were performed for parameters conditioning runoff travel time, such as Manning roughness. We found hourly SWAT is a reliable modelling tool for local level watersheds but needs deliberate attention to the input selection of land use and DEM and calibration process.

The impacts of extreme climates on two watersheds vulnerable to hazards of drought and flooding are examined. Using 2-m resolution topography and land use information, county level soil survey data, meteorology and hydrology data, two daily SWAT models were calibrated in years 2008 to 2010 and validated in years 2012 to 2014. Using the two calibrated models, the meteorology inputs of historical extreme wet (1996) and dry years (1964–65) was selected for daily streamflow simulation using the present land surface and evaluation of changes in the urban hydrology system. Good fit results between simulated and observed streamflow values were achieved for both watersheds, with Nash-Sutcliff coefficient and R2 higher than 0.69 for calibration and 0.66 for validation. The wet year simulation showed that the majority of peakflow events have not increased in both rivers, but baseflow decreased in the upper Christina River in comparison to 1996 records. The dry year simulation indicated that urban development over the last 55 years has led to lower baseflow and greater streamflow variability in both watersheds. The results suggest that improvements are needed in this urban ecosystem to prepare for extreme droughts like the 1960s, and effective stormwater management practices should continue for controlling stormwater runoff. Both these improvements will build resilience in the urban environment.

Background The Antarctic minke whale (Balaenoptera bonaerensis) is a relatively small baleen whale species and is well suited to life in the Antarctic pack ice. Information on their individual movement and distribution patterns is largely unknown due to their association with sea ice habitat where direct observations are limited. The primary objectives of this study are (1) to use satellite telemetry to quantify the movement patterns, distribution, and presumed foraging areas of Antarctic minke whales and (2) to assess the environmental conditions that are associated with areas used by minke whales along the western Antarctic Peninsula. Results Individual movement patterns from three Antarctic minke whales fitted with ARGOS-linked transmitters were analyzed with respect to environmental conditions. Behavioral states were identified using the Multi-Scale Straightness Index. Satellite telemetry revealed disparate behavioral patterns between these three individuals. Generalized additive model analysis demonstrated environmental variables, particularly sea ice, bathymetry, and sea surface temperature, are the best predictors of presumed foraging areas. Conclusions Satellite telemetry from three individuals revealed Antarctic minke whale summer foraging spaces are highly individualized but can generally be associated with pack ice habitat over the continental shelf. The coupled relationship between minke whales, krill, and sea ice suggests that these whales may be sensitive to changes in sea ice concentration, extent, and duration, making them particularly vulnerable to climate change.

This paper develops a multiobjective optimization model to consider transportation impacts of the future development of land. The output of the model is the best location and type of land use that has minimal negative transportation effects and uses the maximum available public transportation infrastructure. It provides tools for both planners and transportation engineers and enables them to consider different scenarios of possible policies and land development. Since multiple objectives and their nonlinear structures are considered, the model is solved using mixed integer nonlinear programming. The final results are shown in both tabular and graphical format. The effectiveness of the model is applied to the northern part of New Castle County, Delaware. The results show that the model successfully finds the best locations for both residential and commercial land uses in order to meet several criteria discussed in the paper.

This work evaluates two distinct calculations of central tendency for sea-ice thickness and quantifies the impact such calculations have on ice volume for the Southern Ocean. The first calculation, area-weighted average thickness, is computed from polygonal ice features and then upscaled to regions. The second calculation, integrated thickness, is a measure of the central value of thickness categories tracked across different scales and subsequently summed to chosen regions. Both methods yield the same result from one scale to the next, but subsequent scales develop diverging solutions when distributions are strongly non-Gaussian. Data for this evaluation are sea-ice stage-of-development records from US National Ice Center ice charts from 1995 to 1998, as proxy records of ice thickness. Results show regionally integrated thickness exceeds area-weighted average thickness by as much as 60% in summer with as few as five bins in thickness distribution. Year-round, the difference between the two calculations yields volume differences consistently >10%. The largest discrepancies arise due to bimodal distributions which are common in ice charts based on current subjective-analysis protocols. We recommend that integrated distribution be used for regional-scale sea-ice thickness and volume estimates from ice charts and encourage similar testing of other large-scale thickness data archives.

During late winter 2007, coincident measurements of sea ice were collected using various sensors at an ice camp in the Beaufort Sea, Canadian Arctic. Analysis of the archived data provides new insight into sea-ice isostasy and its related R-factor through case studies at three scales using different combinations of snow and ice thickness components. At the smallest scale (R-factor is allowed to vary: ranging from 2 to 12, with mean of 5.17, mode of 5.88 and skewed distribution. At regional scales, underwater, airborne and spaceborne platforms are always missing thickness variables from either above or below sea level. For such situations, realistic agreement is found by applying small-scale skewed ranges for the R-factor. These findings encourage a broader isostasy solution as a function of potential energy and length scale. Overall, results add insight to data collection strategies and metadata characteristics of different thickness products.

Chickaloon Flats, Kenai National Wildlife Refuge, is a 10,000 ha tidal mudflat complex on the Kenai Peninsula in southcentral Alaska. It is a protected coastal estuary stopover area along the Pacific Flyway, covering 7% of the total estuarine intertidal area from Cook Inlet to Prince William Sound. Because Chickaloon Flats is historically an important avian migratory stopover and has relative regional importance in terms of estuarine intertidal area, there was a need to evaluate the current vegetation and determine any changes since the last ground study in 1972. We collected land cover data at a sample of ground-truthed points on Chickaloon Flats during 2009–2010 to evaluate existing vegetation communities as compared to historic 1970–71 values. A maximum likelihood supervised classification was performed on 2005 Landsat TM imagery to create an updated land cover classification of Chickaloon Flats. We used two different analytical approaches to show that the most notable changes in land cover types from 1975–2005 were the increase in early successional communities and a decline in unvegetated mud. Additionally, inland land cover types, which represent the more stable marsh-like communities, decreased in area as a whole. The documented changes in vegetation composition and structure over the four decade study period are attributable to elevation changes from sediment accretion and post-1964 Earthquake subsidence. As a result, evidence points to reduced shorebird use of the Flats.

Childers, D.P.; Madsen, J.A.; Krantz, D.E., and Deliberty, T.L., 2019. Constraining the geometry of subsurface paleochannels beneath Delaware Bay and the Mid-Atlantic inner continental she...