114
Multiscale Hydrologic Remote Sensing: Perspectives and Applications
30% of the total events (Kogan 1998). Recent extreme hydroclimatic events in the
east and southeast regions of the United States include droughts in Maryland and
the Chesapeake Bay area in 2001–2002, the Peace River and Lake Okeechobee in
South Florida in 2006, and Lake Lanier in Atlanta, GA in 2007. The occurrence
of droughts in several regions has led to studies on their impact, mostly on water
availability or water shortage with regard to public needs and ecosystem conservation (Haase 2009). All these weather events impact ecosystem processes and services, triggering a need for advanced ecohydrologic studies, especially in coastal
urban regions where most of the population live. As a consequence, urban hydrology or hydrometeorology is playing a pivotal role on regional water balance and
conservation.
Cities in subtropical or temperate regions with ample precipitation will not be
spared the flood and drought impacts arising from global climate change. Especially,
urban regions are more vulnerable to climate change impacts, and many of these
regions have grown large enough to affect the hydrologic characteristics due to
continuous urban sprawl and expansion. This is because urbanization increases the
impervious area and decreases the vegetation cover, which weakens the urban infiltration and flood storage capacity. In short, urbanization brings surging demand in
response to flood and drought control, water supply, urban drainage, and infrastructures. Conversely, more intense heat conductivity produces more heat than natural
ecological environment, which causes the urban heat island effect and an obvious
increase in evapotranspiration (ET). To better understand urban land use dynamics
and water sustainability in urban regions, a resilience theory offers insights into the
behavior of complex systems and characterizes the importance of system criteria
such as system memory, self-organization, and diversity (Adger et al. 2005; Allenby
and Fink 2005). On a long-term basis, remote sensing technologies, as demonstrated
in this study, may provide us with quantitative ways of measuring urban system
adaptive capacity in relation to system memory, self-organization, and diversity over
seasons and identify emerging threshold limits in the assessment of ecosystem resilience in urban regions (Blackmore and Plant 2008). These relevant events in relation to urban system adaptive capacity mainly include, but are not limited to, flood,
drought, and water pollution, which first require a comprehensive understanding in
connection with the density and intensification of the soilborne properties such as
soil moisture, ET, and vegetation cover.
Soil moisture and ET are the two major elements of the water cycle. Soil moisture
is important to the growth and survival of plants. Its availability depends on the
frequency and amount of precipitation, evaporation rate, soil type, vegetation cover,
slope, and depth of groundwater table. Soil moisture has vital significance to climate,
hydrology, ecology, and agriculture and also indicates the storage of water in the soil
available for evaporation. Soil moisture and ET are affected by both water and energy
balances in the soil–vegetation–atmosphere system, which involves many complex
processes in the hydrologic cycle and ecosystem dynamics at the earth’s surface.
The traditional method for measuring soil moisture is in situ, which can accurately
assess the moisture content of soil profile from simple point measurements. Field
campaigns, however, are not only time consuming but also difficult to measure with
high efficiency over larger regions. The use of advanced sensing, monitoring, and
Multiscale Hydrologic Remote Sensing: Perspectives and Applications
30% of the total events (Kogan 1998). Recent extreme hydroclimatic events in the
east and southeast regions of the United States include droughts in Maryland and
the Chesapeake Bay area in 2001–2002, the Peace River and Lake Okeechobee in
South Florida in 2006, and Lake Lanier in Atlanta, GA in 2007. The occurrence
of droughts in several regions has led to studies on their impact, mostly on water
availability or water shortage with regard to public needs and ecosystem conservation (Haase 2009). All these weather events impact ecosystem processes and services, triggering a need for advanced ecohydrologic studies, especially in coastal
urban regions where most of the population live. As a consequence, urban hydrology or hydrometeorology is playing a pivotal role on regional water balance and
conservation.
Cities in subtropical or temperate regions with ample precipitation will not be
spared the flood and drought impacts arising from global climate change. Especially,
urban regions are more vulnerable to climate change impacts, and many of these
regions have grown large enough to affect the hydrologic characteristics due to
continuous urban sprawl and expansion. This is because urbanization increases the
impervious area and decreases the vegetation cover, which weakens the urban infiltration and flood storage capacity. In short, urbanization brings surging demand in
response to flood and drought control, water supply, urban drainage, and infrastructures. Conversely, more intense heat conductivity produces more heat than natural
ecological environment, which causes the urban heat island effect and an obvious
increase in evapotranspiration (ET). To better understand urban land use dynamics
and water sustainability in urban regions, a resilience theory offers insights into the
behavior of complex systems and characterizes the importance of system criteria
such as system memory, self-organization, and diversity (Adger et al. 2005; Allenby
and Fink 2005). On a long-term basis, remote sensing technologies, as demonstrated
in this study, may provide us with quantitative ways of measuring urban system
adaptive capacity in relation to system memory, self-organization, and diversity over
seasons and identify emerging threshold limits in the assessment of ecosystem resilience in urban regions (Blackmore and Plant 2008). These relevant events in relation to urban system adaptive capacity mainly include, but are not limited to, flood,
drought, and water pollution, which first require a comprehensive understanding in
connection with the density and intensification of the soilborne properties such as
soil moisture, ET, and vegetation cover.
Soil moisture and ET are the two major elements of the water cycle. Soil moisture
is important to the growth and survival of plants. Its availability depends on the
frequency and amount of precipitation, evaporation rate, soil type, vegetation cover,
slope, and depth of groundwater table. Soil moisture has vital significance to climate,
hydrology, ecology, and agriculture and also indicates the storage of water in the soil
available for evaporation. Soil moisture and ET are affected by both water and energy
balances in the soil–vegetation–atmosphere system, which involves many complex
processes in the hydrologic cycle and ecosystem dynamics at the earth’s surface.
The traditional method for measuring soil moisture is in situ, which can accurately
assess the moisture content of soil profile from simple point measurements. Field
campaigns, however, are not only time consuming but also difficult to measure with
high efficiency over larger regions. The use of advanced sensing, monitoring, and