Determination of subcatchment and watershed boundaries in a complex and highly urbanized landscape

Urban development significantly alters the landscape by introducing widespread impervious surfaces, which quickly convey surface run‐off to streams via stormwater sewer networks, resulting in “flashy” hydrological responses. Here, we present the inadequacies of using raster‐based digital elevation models and flow‐direction algorithms to delineate large and highly urbanized watersheds and propose an alternative approach that accounts for the influence of anthropogenically modified land cover. We use a semi‐automated approach that incorporates conventional drainage networks into overland flow paths and define the maximal run‐off contributing area. In this approach, stormwater pipes are clustered according to their slope attributes, which define flow direction. Land areas drained by each cluster and contributing (or exporting) flow to a topographically delineated catchment were determined. These land masses were subsequently added or removed from the catchment, modifying both the shape and the size. Our results in a highly urbanized Toronto, Canada, area watershed indicate a moderate net increase in the directly connected watershed area by 3% relative to a topographically forced method; however, differences across three smaller scale subcatchments are greater. Compared to topographic delineation, the directly connected watershed areas of both the upper and middle subcatchments decrease by 5% and 8%, respectively, whereas the lower subcatchment area increases by 15%. This is directly related to subsurface storm sewer pipes that cross topographic boundaries. When directly connected subcatchment area is plotted against total streamflow and flashiness indices using this method, the coefficients of variation are greater (0.93 to 0.97) compared to the use of digital elevation model‐derived subcatchment areas (0.78 to 0.85). The accurate identification of watershed and subcatchment boundaries should incorporate ancillary data such as stormwater sewer networks and retention basin drainage areas to reduce water budget errors in urban systems.     

Elastic source model of the North Mono eruption (1325–1368 A.D.) based on shoreline deformation

Topographic data from the Shuttle Radar Topography Mission (SRTM) captures the permanent deformation of a prominent highstand of Mono Lake, California USA. Deformation of the Dechambeau Ranch highstand shoreline was measured using the elevation of the beach berm—shoreline bluff break-in-slope. Point source models and a boundary element dike model were used to approximate the source of deformation underneath the northern end of the Mono Craters. The point source model could not adequately explain the observed deformation. The dike model yielded the best results for a NW trending dike dipping 60° NE and inflated to widths greater than 60 m. The results suggest that the geometry of the source is more complex than a simple vertical dike and that the deformation is better explained with a dipping dike following a normal fault, or an elongated cryptodome.     

Symplectic Mappings of Co-orbital Motion in the Restricted Problem of Three Bodies

The dynamics of co-orbital motion in the restricted three-body problem are investigated by symplectic mappings. Analytical and semi-numerical mappings have been developed and studied in detail. The mappings have been tested by numerical integration of the equations of motion. These mappings have been proved to be useful for a quick determination of the phase space structure reflecting the main characteristics of the dynamics of the co-orbital problem.     

Using Ground‐Penetrating Radar to Examine Spatial Organization at the Late Classic Maya Site of El Baúl,Cotzumalhuapa, Guatemala

The Cotzumalhuapa Nuclear Zone (CNZ) is a Late Classic site consisting of three large architectural compounds linked by a series of stone‐paved causeways and bridges. The majority of the site, however, lies beneath layers of recent tephra, leaving the structure of this settlement largely unknown. This study uses ground‐penetrating radar (GPR) to map the subsurface near El Baúl, one of the main compounds, in order to examine the spatial relationship among urban architectural features. Excavation within areas of the GPR survey provides fine‐grain detail of one major architectural feature in the region, the Gavarrete Causeway. The complimentary nature of these data sets characterizes the architectural organization of the settlement at two scales. Spatial patterning between large‐scale architectural features supports the hypothesis that the CNZ represents an integrated urban center with evidence of planned community organization characteristic of other Late Classic period centers across Mesoamerica.     

Optical properties of solid and liquid sulfur at visible and infrared wavelengths

Knowledge of the optical constants of elemental sulfur has potential applications to Venus, Jupiter, Io, Amalthea, and the Earth. The real part, n, of the index of refraction of liquid sulfur (at 133°C) and of solid orthorhombic sulfur (at 25°C) for the wavelength range 0.4–2.0 μm were measured ellipsometrically. The imaginary part, k, of the refractive index of liquid sulfur was obtained by transmittance measurements at the same temperature and wavelength range. The reflectance of semi-infinite slabs of solid and liquid sulfur is calculated using the measured n and k values. We confirm that sulfur melts on Io would be classified as “black” by the Voyager imaging system.     

Die Entwickelung und das Auftreten des Paläozoikums in Griechenland

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