\textcopyright} 2014 Elsevier B.V. Coastal mangroves lose large amounts of water through evapotra... more \textcopyright} 2014 Elsevier B.V. Coastal mangroves lose large amounts of water through evapotranspiration (ET) that can be equivalent to the amount of annual rainfall in certain years. Satellite remote sensing can play a crucial role in identifying regional ET trends and surface energy changes after disturbances in isolated and inaccessible areas of coastal mangrove wetlands, like those found in Everglades National Park in southern Florida. Using a combination of long-term datasets acquired from the NASA Landsat 5TM satellite database and the Florida Coastal Everglades Long-Term Ecological Research project, the present study investigates how ET as well as radiation and other energy balance parameters in the Everglades mangrove ecotone have responded to multiple hurricane events and restoration projects over the past two decades. An energy balance model using satellite data was used to estimate latent heat ($\lambda$E) in tall and scrub mangrove environments. An eddy-covariance tower and weather tower supplied long-term data of multiple environmental and meteorological parameters that were used in calibrating and testing the modeled results from the Landsat images. Results identified significant differences in $\lambda$E and soil heat flux measurements between the tall and scrub, and fringe and basin mangrove environments. The scrub mangrove site had the lowest $\lambda$E rates, highest soil heat flux and lowest biophysical index (i.e., Fractional Vegetation Cover (FVC), Normalized Difference Vegetation Index (NDVI), and Soil-Adjusted Vegetation Index (SAVI) values. Mangrove damage and mortality associated with two strong hurricanes decreased FVC, NDVI, and SAVI, and increased soil heat flux at the tall mangrove site located in a basin-type environment. Recovery of the spectral characteristics, energy balance parameters and $\lambda$E following hurricane disturbance was quicker in fringe mangroves than in basin mangroves. Latent heat fluxes ($\lambda$E) were also relatively high after each storm and may have increased as a result of increasing vapor pressure deficits. Remote sensing of the surface energy balance and $\lambda$E of mangrove forests can help our understanding of how these environments respond to disturbances to the landscape and the effect that these changes can have on the energy and water budget. Moreover, relationships between energy and water balance components developed for the coastal mangroves of southern Florida could be extrapolated to other mangrove systems in the Caribbean to measure changes caused by natural events and human modifications.
ABSTRACT It has long been recognized that New Orleans is subsiding and is therefore susceptible t... more ABSTRACT It has long been recognized that New Orleans is subsiding and is therefore susceptible to catastrophic flooding. Here we present a new subsidence map for the city, generated from space-based synthetic-aperture radar measurements, which reveals that parts of New Orleans underwent rapid subsidence in the three years before Hurricane Katrina struck in August 2005. One such area is next to the Mississippi River–Gulf Outlet (MRGO) canal, where levees failed during the peak storm surge: the map indicates that this weakness could be explained by subsidence of a metre or more since their construction.
Characterizing submarine groundwater discharge is important for understanding the impact of nutri... more Characterizing submarine groundwater discharge is important for understanding the impact of nutrients and contaminants on coastal ecosystems. In Biscayne Bay, FL, some of this discharge occurs as discrete flow from a number of springs fed by karst conduits in the bay bottom. Previous studies have shown that flow from these springs is semi-diurnal and occurs near low tide. Since the groundwater temperature (25-26 C) often differs significantly from the surrounding bay water, these springs can produce anomalies in the nearby sea surface temperature. Therefore, aerial survey techniques such as thermal imaging may provide an efficient method for mapping these springs. Unfortunately, the nature of these anomalies is complicated by seasonal and diurnal surface temperature variations, currents, and seasonal flow dynamics. This study uses data from an array of temperature sensors placed at the surface over Ricisak Spring, a known and previously studied spring in western Biscayne Bay, to interpolate and simulate thermal images of the plume associated with the spring. 14 SeaStar CTD temperature sensors were suspended from floats fixed to fiberglass poles set in the bay bottom 2 m apart forming a star-shaped array. An additional sensor placed at a remote site provided a control reference. This array was deployed for 24 hour periods in June 2007 and February 2008 to study the conditions when the plume is either colder or warmer than the surrounding bay temperatures. For the June deployment, bay temperatures at the control station ranged from 28.4 to 31.2 C and resulted in negative temperature anomalies of approximately 2 C across the array during both late afternoon and early morning low tide flow periods. In February, temperatures at the control station ranged from 22.0 to 26.5 C. During the late afternoon low tide flow period, temperatures in the plume were similar to the surrounding bay water. In contrast, the lower bay temperatures in the early morning resulted in positive anomalies of as much as 2 C across the array. These results demonstrate that the surface temperature expression from this and similar springs in Biscayne Bay can be detected with 1-2 m resolution aerial thermal imagery.
Aquifer porosity characterization is often derived from measurements of borehole-gravity, acousti... more Aquifer porosity characterization is often derived from measurements of borehole-gravity, acoustic, neutron, and density logs as well as analysis of core samples. Electrical anisotropy measurements play an important role in estimating the direction of porosity and fluid flow in porous media and can be determined noninvasively. Knowledge of anisotropy in the Biscayne Aquifer rocks may indicate a preferred direction of secondary porosity which has been formed through the dissolution of limestone. In this study azimuthal resistivity measurements at 13 sites in Miami-Dade County, FL were used to investigate anisotropy of the electrical resistivity structure and to estimate the anisotropic secondary porosity of the Biscayne Aquifer. The coefficient of anisotropy ranged from 1.01 - 1.36 with the highest values beneath the Atlantic Costal Ridge near the east coast while lower values are generally in the low elevation areas on the margin of the Everglades to the west. The general trend of m...
ABSTRACT Characterizing submarine groundwater discharge is important for understanding the impact... more ABSTRACT Characterizing submarine groundwater discharge is important for understanding the impact of nutrients and contaminants on coastal ecosystems. In Biscayne Bay, FL, some of this discharge occurs as discrete flow from a number of springs fed by karst conduits in the bay bottom. Previous studies have shown that flow from these springs is semi-diurnal and occurs near low tide. Since the groundwater temperature (25-26 C) often differs significantly from the surrounding bay water, these springs can produce anomalies in the nearby sea surface temperature. Therefore, aerial survey techniques such as thermal imaging may provide an efficient method for mapping these springs. Unfortunately, the nature of these anomalies is complicated by seasonal and diurnal surface temperature variations, currents, and seasonal flow dynamics. This study uses data from an array of temperature sensors placed at the surface over Ricisak Spring, a known and previously studied spring in western Biscayne Bay, to interpolate and simulate thermal images of the plume associated with the spring. 14 SeaStar CTD temperature sensors were suspended from floats fixed to fiberglass poles set in the bay bottom 2 m apart forming a star-shaped array. An additional sensor placed at a remote site provided a control reference. This array was deployed for 24 hour periods in June 2007 and February 2008 to study the conditions when the plume is either colder or warmer than the surrounding bay temperatures. For the June deployment, bay temperatures at the control station ranged from 28.4 to 31.2 C and resulted in negative temperature anomalies of approximately 2 C across the array during both late afternoon and early morning low tide flow periods. In February, temperatures at the control station ranged from 22.0 to 26.5 C. During the late afternoon low tide flow period, temperatures in the plume were similar to the surrounding bay water. In contrast, the lower bay temperatures in the early morning resulted in positive anomalies of as much as 2 C across the array. These results demonstrate that the surface temperature expression from this and similar springs in Biscayne Bay can be detected with 1-2 m resolution aerial thermal imagery.
Shallow ground resistivity was used to image the saline-freshwater mixing zone in the subsurface ... more Shallow ground resistivity was used to image the saline-freshwater mixing zone in the subsurface due to saltwater intrusion at a site less than 2 kilometers from the coastline of Biscayne Bay, an estuary in South Florida. Resistivity arrays have several advantages when applied to coastal groundwater environments. Experiments can be set up to measure several depths by varying the electrode
\textcopyright} 2014 Elsevier B.V. Coastal mangroves lose large amounts of water through evapotra... more \textcopyright} 2014 Elsevier B.V. Coastal mangroves lose large amounts of water through evapotranspiration (ET) that can be equivalent to the amount of annual rainfall in certain years. Satellite remote sensing can play a crucial role in identifying regional ET trends and surface energy changes after disturbances in isolated and inaccessible areas of coastal mangrove wetlands, like those found in Everglades National Park in southern Florida. Using a combination of long-term datasets acquired from the NASA Landsat 5TM satellite database and the Florida Coastal Everglades Long-Term Ecological Research project, the present study investigates how ET as well as radiation and other energy balance parameters in the Everglades mangrove ecotone have responded to multiple hurricane events and restoration projects over the past two decades. An energy balance model using satellite data was used to estimate latent heat ($\lambda$E) in tall and scrub mangrove environments. An eddy-covariance tower and weather tower supplied long-term data of multiple environmental and meteorological parameters that were used in calibrating and testing the modeled results from the Landsat images. Results identified significant differences in $\lambda$E and soil heat flux measurements between the tall and scrub, and fringe and basin mangrove environments. The scrub mangrove site had the lowest $\lambda$E rates, highest soil heat flux and lowest biophysical index (i.e., Fractional Vegetation Cover (FVC), Normalized Difference Vegetation Index (NDVI), and Soil-Adjusted Vegetation Index (SAVI) values. Mangrove damage and mortality associated with two strong hurricanes decreased FVC, NDVI, and SAVI, and increased soil heat flux at the tall mangrove site located in a basin-type environment. Recovery of the spectral characteristics, energy balance parameters and $\lambda$E following hurricane disturbance was quicker in fringe mangroves than in basin mangroves. Latent heat fluxes ($\lambda$E) were also relatively high after each storm and may have increased as a result of increasing vapor pressure deficits. Remote sensing of the surface energy balance and $\lambda$E of mangrove forests can help our understanding of how these environments respond to disturbances to the landscape and the effect that these changes can have on the energy and water budget. Moreover, relationships between energy and water balance components developed for the coastal mangroves of southern Florida could be extrapolated to other mangrove systems in the Caribbean to measure changes caused by natural events and human modifications.
ABSTRACT It has long been recognized that New Orleans is subsiding and is therefore susceptible t... more ABSTRACT It has long been recognized that New Orleans is subsiding and is therefore susceptible to catastrophic flooding. Here we present a new subsidence map for the city, generated from space-based synthetic-aperture radar measurements, which reveals that parts of New Orleans underwent rapid subsidence in the three years before Hurricane Katrina struck in August 2005. One such area is next to the Mississippi River–Gulf Outlet (MRGO) canal, where levees failed during the peak storm surge: the map indicates that this weakness could be explained by subsidence of a metre or more since their construction.
Characterizing submarine groundwater discharge is important for understanding the impact of nutri... more Characterizing submarine groundwater discharge is important for understanding the impact of nutrients and contaminants on coastal ecosystems. In Biscayne Bay, FL, some of this discharge occurs as discrete flow from a number of springs fed by karst conduits in the bay bottom. Previous studies have shown that flow from these springs is semi-diurnal and occurs near low tide. Since the groundwater temperature (25-26 C) often differs significantly from the surrounding bay water, these springs can produce anomalies in the nearby sea surface temperature. Therefore, aerial survey techniques such as thermal imaging may provide an efficient method for mapping these springs. Unfortunately, the nature of these anomalies is complicated by seasonal and diurnal surface temperature variations, currents, and seasonal flow dynamics. This study uses data from an array of temperature sensors placed at the surface over Ricisak Spring, a known and previously studied spring in western Biscayne Bay, to interpolate and simulate thermal images of the plume associated with the spring. 14 SeaStar CTD temperature sensors were suspended from floats fixed to fiberglass poles set in the bay bottom 2 m apart forming a star-shaped array. An additional sensor placed at a remote site provided a control reference. This array was deployed for 24 hour periods in June 2007 and February 2008 to study the conditions when the plume is either colder or warmer than the surrounding bay temperatures. For the June deployment, bay temperatures at the control station ranged from 28.4 to 31.2 C and resulted in negative temperature anomalies of approximately 2 C across the array during both late afternoon and early morning low tide flow periods. In February, temperatures at the control station ranged from 22.0 to 26.5 C. During the late afternoon low tide flow period, temperatures in the plume were similar to the surrounding bay water. In contrast, the lower bay temperatures in the early morning resulted in positive anomalies of as much as 2 C across the array. These results demonstrate that the surface temperature expression from this and similar springs in Biscayne Bay can be detected with 1-2 m resolution aerial thermal imagery.
Aquifer porosity characterization is often derived from measurements of borehole-gravity, acousti... more Aquifer porosity characterization is often derived from measurements of borehole-gravity, acoustic, neutron, and density logs as well as analysis of core samples. Electrical anisotropy measurements play an important role in estimating the direction of porosity and fluid flow in porous media and can be determined noninvasively. Knowledge of anisotropy in the Biscayne Aquifer rocks may indicate a preferred direction of secondary porosity which has been formed through the dissolution of limestone. In this study azimuthal resistivity measurements at 13 sites in Miami-Dade County, FL were used to investigate anisotropy of the electrical resistivity structure and to estimate the anisotropic secondary porosity of the Biscayne Aquifer. The coefficient of anisotropy ranged from 1.01 - 1.36 with the highest values beneath the Atlantic Costal Ridge near the east coast while lower values are generally in the low elevation areas on the margin of the Everglades to the west. The general trend of m...
ABSTRACT Characterizing submarine groundwater discharge is important for understanding the impact... more ABSTRACT Characterizing submarine groundwater discharge is important for understanding the impact of nutrients and contaminants on coastal ecosystems. In Biscayne Bay, FL, some of this discharge occurs as discrete flow from a number of springs fed by karst conduits in the bay bottom. Previous studies have shown that flow from these springs is semi-diurnal and occurs near low tide. Since the groundwater temperature (25-26 C) often differs significantly from the surrounding bay water, these springs can produce anomalies in the nearby sea surface temperature. Therefore, aerial survey techniques such as thermal imaging may provide an efficient method for mapping these springs. Unfortunately, the nature of these anomalies is complicated by seasonal and diurnal surface temperature variations, currents, and seasonal flow dynamics. This study uses data from an array of temperature sensors placed at the surface over Ricisak Spring, a known and previously studied spring in western Biscayne Bay, to interpolate and simulate thermal images of the plume associated with the spring. 14 SeaStar CTD temperature sensors were suspended from floats fixed to fiberglass poles set in the bay bottom 2 m apart forming a star-shaped array. An additional sensor placed at a remote site provided a control reference. This array was deployed for 24 hour periods in June 2007 and February 2008 to study the conditions when the plume is either colder or warmer than the surrounding bay temperatures. For the June deployment, bay temperatures at the control station ranged from 28.4 to 31.2 C and resulted in negative temperature anomalies of approximately 2 C across the array during both late afternoon and early morning low tide flow periods. In February, temperatures at the control station ranged from 22.0 to 26.5 C. During the late afternoon low tide flow period, temperatures in the plume were similar to the surrounding bay water. In contrast, the lower bay temperatures in the early morning resulted in positive anomalies of as much as 2 C across the array. These results demonstrate that the surface temperature expression from this and similar springs in Biscayne Bay can be detected with 1-2 m resolution aerial thermal imagery.
Shallow ground resistivity was used to image the saline-freshwater mixing zone in the subsurface ... more Shallow ground resistivity was used to image the saline-freshwater mixing zone in the subsurface due to saltwater intrusion at a site less than 2 kilometers from the coastline of Biscayne Bay, an estuary in South Florida. Resistivity arrays have several advantages when applied to coastal groundwater environments. Experiments can be set up to measure several depths by varying the electrode
Symposium on the Application of Geophysics to Engineering and Environmental Problems 2014, 2014
ABSTRACT This study presents hydrogeophysical measurements of aquifer anisotropy at an active hyd... more ABSTRACT This study presents hydrogeophysical measurements of aquifer anisotropy at an active hydrological site consisting of a municipal wellfield transversed by a surface drainage canal. 1-D azimuthal electrical soundings, 2-D and 3-D resistivity imaging, and azimuthal self potential gradient (ASPG) techniques were employed together with well data to map the subsurface behavior at Snapper Creek Municipal Well Field, in Miami, Florida. Azimuthal electrical measurements at the site indicate that the direction of minimum resistivity (maximum hydraulic conductivity) changes from NNW-SSE to NE-SW with depth. The 1-D resistivity-depth profile shows a decrease in resistivity between 2 and 4 m depth, followed by a more resistive layer below 4 m depth. The 2-D and 3-D imaging illustrates higher resistivity at the surface in the unsaturated zone followed by a decrease in the saturated zone with significant horizontal and vertical changes due to low resistivity zones. The variation is attributed to solution cavities similar to those evidenced in monitoring well lithology at the site. The measured self potential during pumping and non-pumping of groundwater changes on the average by 3 mV. The estimated potential polarities indicate that flow direction trends SSE which is similar to the trend of azimuthal resistivity survey from the surface to 4 m and the direction of the surface water flow in the canal at the site. The results demonstrate that the change in hydraulic anisotropy might be related to solution cavities, the surface canal and the groundwater extraction wells. This study shows the potential for hydrogeophysical measurement as a useful tool in providing information about the anisotropy in areas of complex surface and groundwater interaction.
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