Theodore A. Endreny

Maximizing spatial congruence of observed and DEM-delineated overland flow networks

Model simulated overland flow is traditionally routed by the terrain-based algorithms that read 90 to 10-m pixel data, yet observed flow is often influenced by sub-meter micro-terrain features. While sub-meter terrain maps are not available for most watersheds, routing algorithms that bifurcate flow through multiple pixel boundaries may function to match observed runoff patterns. This paper assesses the spatial congruence between observed overland flow from two agricultural hillslopes in New Jersey with 30-m pixel flowpaths predicted by five common routing algorithms known as D8, Multiple Flow, 2D-Lea, (a building block in DEMON), 2D-Jensen, and D-Infinity. The lowest congruence ratings were assigned to D8, which constrained flow to a single neighbour, and MF, which bifurcated flow into all neighbours lower in elevation. 2D-Lea and D-Infinity, algorithms that bifurcated flow to a maximum of two neighbours, achieved the highest accuracy rankings. Simple algorithm modifications that increased D8 bifurcation, and constrained MF bifurcation, resulted in congruence rankings that rivaled the more sophisticated 2D-Lea, 2D-Jensen, and D-Infinity results. These experiments support the use of flow bifurcation schemes that pass flow into a maximum of between two and three pixels when routing polluted runoff.

Detailed river stage mapping and head gradient analysis during meander cutoff in a laboratory river

Analytical models of river evolution predict meander narrowing and elongation which creates sinuosity-driven hyporheic exchange across the meander neck, by decreasing flow distance and increasing head loss. We used a laboratory river table and close range photogrammetry to map and analyze sinuosity as a driver of head gradients and hyporheic exchange during cutoff. The river valley had relatively high slopes (1.8%) and moderately cohesive sediment (10% talc, 90% sand) to facilitate cutoff, and ratios of horizontal to vertical scaling were distorted to achieve dynamic similitude (Re = 3200). Incipient to cutoff, the head gradient across the neck increased due to a narrowing neck, upstream aggradation, and downstream degradation. Longitudinal and transverse river surface slopes around the meander bend increased as the meander approached cutoff. The steep head gradient across the moderately cohesive meander neck generated seepage erosion and scour that formed a low-sinuosity avulsion. Sediment-rich flow in the avulsed channel aggraded the downstream bed and separated the active channel and oxbow lake. The limitation in geometric and dynamic similitude in the river table limits extrapolation to natural rivers, yet river evolution may involve aggradation and degradation induced channel head loss and turnover hyporheic exchange as well as seepage-induced meander neck erosion. Our submillimeter maps of meander morphology and water stage provide data to parameterize river evolution and hyporheic exchange models, and may inform analysis and mapping of field sites.

Assessing urban forest effects and values: Toronto's urban forest

An analysis of trees in Toronto, Ontario, reveals that this city has about 10.2 million trees with a tree and shrub canopy that covers approximately 26.6 percent of the city. The most common tree species are eastern white-cedar, sugar maple, and Norway maple. The urban forest currently stores an estimated 1.1 million metric tons of carbon valued at CAD

Short note: Monitoring soil moisture and water table height with a low-cost data logger

25.0 million. In addition, these trees remove about 46,700 metric tons of carbon per year (CAD

A Comparison of Hyporheic Transport at a Cross‐Vane Structure and Natural Riffle

1.1 million per year) and about 1,905 metric tons of air pollution per year (CAD

Robustness of pollutant loading estimators for sample size reduction in a suburban watershed

16.9 million per year). Trees in Toronto are estimated to reduce annual residential energy costs by CAD

River Surface Water Topography Mapping at Sub-Millimeter Resolution and Precision With Close Range Photogrammetry: Laboratory Scale Application

9.7 million per year. The compensatory value is estimated at CAD

Bioretention column study of bacteria community response to salt-enriched artificial stormwater.

7.1 billion. Information on the structure and functions of the urban forest can be used to improve and augment support for urban forest management programs and to integrate urban forests within plans to improve environmental quality in the Toronto area.

Estimating recharge rates for qanat-based water supply in northern Cyprus: a case study using remotely sensed and in-situ data

Comprehensive temporal data sets are often needed in geosciences to understand and model environmental phenomena. Time series data sets in the geosciences have traditionally been captured by costly commercial sensors and data loggers (

Hydraulic complexity at a large river confluence in the Amazon basin

100–1000s). Dedrick et al. (2000) presented a less costly (