H22B-01
Landsat-Based Impervious Surface Mapping And Storm Runoff Response Modeling
The hydrologic response of urbanized watersheds is greatly affected by the extent of fractional impervious surface (FIS) area. Impervious surfaces effect on ecohydrology of watersheds include reduction of infiltration, soil moisture storage, natural interception and depression storage, base flow and groundwater recharge, increase peak discharge, reduction in time to peak and time of concentration. These effects have important ecological and economic impact on the hydrology of watersheds. Thus accurate estimation of these surfaces is an important part of urban watershed management. For larger areas, it has been shown that remote sensing of these surfaces using standard procedures is practical and cost effective. Estimation of FIS areas using Landsat imagery for two watersheds of different settings (Simms Creek, Florida and Red River basin of the North @ Grand Forks, North Dakota) was conducted. The respective storm runoff response was studied using a spatially distributed storm runoff model based n the concept of travel time and temporal comparisons were made. For Simms Creek, the increase in urban built-up areas in the year 2000 compared to 1984 increased the peak flow by 16.2% and reduced the time required to attain the peak flow 18.1%. The results at the Red River basin of the North show that an increase in impervious areas (FIS >0.5) (by 79% from 1974 to 2001) attributed to the growing cities in the Red River Basin for the period of study. Hydrograph analysis of the flow at Grand Forks gauging station also indicated runoff response of the basin has increased between 1993 and 2002 with all years having percent runoff greater than 10% compared to only 35% of the years between 1974 and 1993. Keywords: Landsat; storm runoff, Land-cover; impervious surface area, Simms Creek; Red River
H22B-02
City Expansion And The Tradgedy Of The Commons: The Case Of Lagos, Nigeria
The conflict between the short-term welfare of individuals and the long-term welfare of the society as described by Hardins (1968) always pose serious risk of degradation to the basic life support systems. This scenario is aptly demonstrated by the voracious expansion of cities especially in the developing countries and emerging economies of the world. The risk of degradation which poses serious risks to the functioning of the global commons is even more serious where the city is ‘evolving' with little or no planning measures to guide city growth and development. The city of Lagos, Nigeria's former capital with a population of over 9million classically exemplifies this case. This study integrates archived base data (maps and aerial photographs) and medium resolution remote sensing data to characterise the spatial evolution of the city of Lagos in over 4 decades (between 1960 and 2005). Specifically, quantitative assessment of the extent and impact of Lagos city expansion on critical ecosystems (wetlands, waterbodies natural/semi natural vegetations, and wilderness) was estimated. In addition, the impact of the loss of supporting, regulating, and cultural functions of natural ecosystems on urban flooding, city temperature/heat islands, and aesthetics in the city is also analysed. The implications of the results both for human health, and as advocacy tool for city planning and management options are also discussed.
H22B-03
Effects of Global Change on U.S. Urban Areas: Vulnerabilities, Impacts, and Adaptation
Human settlements, both large and small, are where the vast majority of people on the Earth live. Expansion of
cities both in population and areal extent, is a relentless process that will accelerate in the 21st century. As a
consequence of urban growth both in the United States and around the globe, it is important to develop an
understanding of how urbanization will affect the local and regional environment. Of equal importance, however,
is the assessment of how cities will be impacted by the looming prospects of global climate change and climate
variability. The potential impacts of climate change and variability has recently been enunciated by the IPCC's
"Climate Change 2007" report. Moreover, the U.S. Climate Change Science Program (CCSP) is preparing a
series of "Synthesis and Assessment Products" (SAP) reports to support informed discussion and decision
making regarding climate change and variability by policy makers, resource managers, stakeholders, the media,
and the general public. We are working on a chapter of SAP 4.6 ("Analysis of the Effects of Global Chance on
Human Health and Welfare and Human Systems") wherein we wish to describe the effects of global climate
change on human settlements. This paper will present the thoughts and ideas that are being formulated for our
SAP report that relate to what vulnerabilities and impacts will occur, what adaptation responses may take place,
and what possible effects on settlement patterns and characteristics will potentially arise, on human settlements
in the U.S. as a result of climate change and climate variability. We wish to present these ideas and concepts as
a "work in progress" that are subject to several rounds of review, and we invite comments from listeners at this
session on the rationale and veracity of our thoughts. Additionally, we wish to explore how technology such as
remote sensing data coupled with modeling, can be employed as synthesis tools for deriving insight across a
spectrum of impacts (e.g. public health, urban planning for mitigation strategies) on how cities can cope and
adapt to climate change and variability. This latter point parallels the concepts and ideas presented in the U.S.
National Academy of Sciences, Decadal Survey report on "Earth Science Applications from Space: National
Imperatives for the Next Decade and Beyond" wherein the analysis of the impacts of climate change and
variability, human health, and land use change are listed as key areas for development of future Earth observing
remote sensing systems.
http:www.climatescience.gov/Library/sap/sap4-6/default.php
H22B-04
Remote sensing and ecosystem modeling for monitoring urban ecosystems
As an increasingly larger fraction of people is living in cities, there is a growing interest in understanding how the mosaic of buildings, roads, concretes, grassy lawns, gardens and other exotic vegetation functions as an ecosystem and how urban ecosystems services can be enhanced to ensure adequate quality of life to the bulk of the global population. High resolution remote sensing allows separating the mosaic components and their functions with high degree of precision over small surfaces. On the other hand, moderate to coarse resolution remote sensing integrated with ground observations and modeling provides a feasible approach for studying the functioning of these ecosystems and their impacts on the carbon and water cycles across a wide range of geographical settings. Here we present a summary of continental scale analyses based on satellite data from the DMSP/OLS, MODIS, and ecosystem modeling to quantify the impact of urban development on the terrestrial carbon and water cycle in the United States. The results show that urban ecosystems can maintain significantly high levels of photosynthetic capacity, but with fluxes varying largely as a function of vegetation management. Periodical monitoring of these impacts at the regional scale is critical for the appropriate management of urban growth and the sustainable use of natural resources. We will discuss the limitations of the current tools and required sensor improvements for the continued monitoring of these impacts.
H22B-05
Mapping Global Urban Extent and Intensity for Environmental Monitoring and Modeling
The human dimensions of global environmental change have received increased attention in policy, decision- making, research, and even the media. However, the influence of urban areas in global change processes is still often assumed to be negligible. Although local environmental conditions such as the urban heat island effect are well-documented, little or no work has focused on cross-scale interactions, or the ways in which local urban processes cumulatively impact global changes. Given the rapid rates of rural-urban migration, economic development and urban spatial expansion, it is becoming increasingly clear that the ‘ecological footprint' of cities may play a critical role in environmental changes at regional and global scales. Our understanding of the cumulative impacts of urban areas on natural systems has been limited foremost by a lack of reliable, accurate data on current urban form and extent at the global scale. The data sets that have emerged to fill this gap (LandScan, GRUMP, nighttime lights) suffer from a number of limitations that prevent widespread use. Building on our early efforts with MODIS data, our current work focuses on: (1) completing a new, validated map of global urban extent; and (2) developing methods to estimate the subpixel fraction of impervious surface, vegetation, and other land cover types within urbanized areas using coarse resolution satellite imagery. For the first task, a technique called boosting is used to improve classification accuracy and provides a means to integrate 500 m resolution MODIS data with ancillary data sources. For the second task, we present an approach for estimating percent cover that relies on continuous training data for a full range of city types. These exemplars are used as inputs to fuzzy neural network and regression tree algorithms to predict fractional amounts of land cover types with increased accuracy. Preliminary results for a global sample of 100 cities (which vary in population size, level of economic development, and spatial extent) show good agreement with the expected morphology in each region.
H22B-06
Using Time-Series of Impervious Cover and Tree Cover to Study Urban Dynamics in the Upper Delaware River Basin
We have developed and tested a satellite-based regional land cover/use monitoring protocol. The approach is based on well-established algorithms used with coarse resolution satellite data and uses state-of-the-art processing techniques, including atmospheric corrections. Sub-pixel fractions of impervious cover and tree cover are derived at the 28.5m spatial resolution of the Landsat satellite data using air photography and used to detect and monitor urban growth and dynamics in the Upper Delaware River Watershed, which comprises a major water supply of urban centers such as New York City. A pilot project that examines urban growth patterns in Upper Delaware River Basin from 1984 to 2005 is presented as a demonstration of the protocols and includes field validation. These data are being used to simulate urban growth into the future and are an important tool for decision-making and urban planning in the entire watershed.