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Abstract. Compound floods are an active area of research in which the complex interaction between pluvial, fluvial, coastal and groundwater flooding are analyzed. A number of studies have simulated the compound flooding impacts of precipitation, river discharge and storm surge variables with different numerical models and linking techniques. However, groundwater flooding is often neglected in flood risk assessments due to its sporadic frequency (as most regions have water tables sufficiently low that do not
exacerbate flooding conditions), isolated impacts and considerably lower
severity with respect to other types of flooding. This paper presents a
physics-based, loosely coupled modeling framework using FLO-2D and
MODFLOW-2005 that is capable of simulating surface–subsurface water
interactions. FLO-2D, responsible for the surface hydrology and infiltration processes, transfers the infiltration volume as recharge to MODFLOW-2005 until the soil absorption capacity is exceeded, while MODFLOW-2005 returns exchange flow to the surface when the groundwater heads are higher than the surface depth. Three events characterized by short-duration intense precipitation, average tide levels and unusually high water table levels are used to assess the relevance of groundwater flooding in the Arch Creek Basin, a locality in North Miami particularly prone to flooding conditions. Due to limitations in water level observations, the model was calibrated based on properties that have experienced repetitive flooding losses and validated using image-based volunteer geographic information (VGI). Results suggest that groundwater-induced flooding is localized, and high groundwater heads influence pluvial flooding as the shallow water table undermines the soil infiltration capacity. Understanding groundwater flood risk is of particular interest to low-elevation coastal karst environments as the
sudden emergence of the water table at ground surface can result in social
disruption, adverse effects to essential services and damage to infrastructure. Further research should assess the exacerbated impacts of
high tides and sea level rise on water tables under current and future
climate projections.

Studies of trophic-level material and energy transfers are central to ecology. The use of isotopic tracers has now made it possible to measure trophic transfer efficiencies of important nutrients and to better understand how these materials move through food webs. We analyzed data from thirteen N-15-ammonium tracer addition experiments to quantify N transfer from basal resources to animals in headwater streams with varying physical, chemical, and biological features. N transfer efficiencies from primary uptake compartments (PUCs; heterotrophic microorganisms and primary producers) to primary consumers was lower (mean 11.5%, range 100%). Total N transferred (as a rate) was greater in streams with open compared to closed canopies and overall N transfer efficiency generally followed a similar pattern, although was not statistically significant. We used principal component analysis to condense a suite of site characteristics into two environmental components. Total N uptake rates among trophic levels were best predicted by the component that was correlated with latitude, DIN:SRP, GPP:ER, and percent canopy cover. N transfer efficiency did not respond consistently to environmental variables. Our results suggest that canopy cover influences N movement through stream food webs because light availability and primary production facilitate N transfer to higher trophic levels. ; National Science FoundationNational Science Foundation (NSF) [NSF-DEB 1052399, DBI-1401954]; Department of Energy's Office of Science, Biological and Environmental Research; U.S. DOEUnited States Department of Energy (DOE) [DE-AC05-00OR22725]; U.S. Department of EnergyUnited States Department of Energy (DOE) [DE-AC05-00OR22725] ; We thank everyone who participated in the individual tracer experiments used in this analysis. We are grateful for the leadership and friendship of the late Pat Mulholland, whose legacy continues to inspire. This manuscript is the product of a workshop funded by a National Science Foundation grant (NSF-DEB 1052399) to M. R. Whiles and W. K. Dodds. Partial support during manuscript preparation to N. A. Griffiths was from the Department of Energy's Office of Science, Biological and Environmental Research. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the U.S. DOE under contract DE-AC05-00OR22725. This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. S. M. Collins was supported by a National Science Foundation Postdoctoral Research Fellowship in Biology (DBI-1401954). ; Public domain authored by a U.S. government employee