Impervious surface estimation using remote sensing images and gis : how accurate is the estimate at subdivision level?

Impervious surface has long been accepted as a key environmental indicator linking development to its impacts on water. Many have suggested that there is a direct correlation between degree of imperviousness and both quantity and quality of water. Quantifying the amount of impervious surface, however, remains difficult and tedious especially in urban areas. Lately more efforts have been focused on the application of remote sensing and GIS technologies in assessing the amount of impervious surface and many have reported promising results at various pixel levels. This paper discusses an attempt at estimating the amount of impervious surface at subdivision level using remote sensing images and GIS techniques. Using Landsat ETM+ images and GIS techniques, a regression tree model is first developed for estimating pixel imperviousness. GIS zonal functions are then used to estimate the amount of impervious surface for a sample of subdivisions. The accuracy of the model is evaluated by comparing the model-predicted imperviousness to digitized imperviousness at the subdivision level. The paper then concludes with a discussion on the convenience and accuracy of using the method to estimate imperviousness for large areas

Zoning, TDRs, and the Density of Development

Many communities on the urban fringe are implementing a range of policies to preserve farmland and open space, cluster residential development, and guide development to areas with existing infrastructure. These efforts are an attempt to control overall growth and the concomitant loss in open space and also to counter a trend toward the so-called large lot development that often takes place in these areas. Planners have argued that policies to manage density are the most important local policy focus for urban areas in the coming years. It is possible that large lot development and sprawl are themselves the result of government policy. Most local governments use zoning to establish minimum acreage requirements for each residential dwelling unit; in ex-urban localities, these limits are often quite high. Developers might build a subdivision with average lot sizes greater than the minimum but they cannot by law go below it. Some researchers have argued, however, that the spatial patterns of development are simply the natural result of household preferences and market forces. In this paper, we address the question of whether zoning limits are the primary cause of lowdensity, sprawling development or whether market forces tend to dictate this outcome. If zoning limits account for low-density development in at least some cases, how would development patterns be different if there had been no such rules? We begin by constructing a simple model of the developer decision about the density of new development. The subdivision is the unit of observation, and developers must weigh both demand and cost considerations in choosing density, in addition to complying with zoning restrictions that vary across parcels. We apply the model using parcel-level data from a region where zoning rules vary but are exogenous to the period under study. Calvert County, Maryland, near Washington, DC, is an historically rural county that has experienced rapid growth in recent years. The county has a transferable development rights (TDRs) program that has led to a great deal of variability in the intensity of development across properties. We are able to not only examine the extent to which zoning has contributed to large lot development but also to determine the economic forces that underlie density decisions. Finally, we are able to forecast how density would have been different in the absence of zoning rules by estimating a Tobit equation that is censored for the observations constrained by zoning.housing density, zoning, transferable development rights

The Effects of Subdivision Design on Housing Values: The Case of Alleyways

Subdivision design likely impacts residential housing values. This study examines the sale prices of houses located in subdivisions utilizing rear-entry alleyways in the Greater Dallas-Fort Worth-Denton metroplex. Regression analysis on a sample of 1,672 home sales, some of which are located on alleyways, reveals statistically significant impacts. Consequently, developers, appraisers, New Urbanists and other real estate participants should consider subdivision design when estimating value for residential dwellings.

The validation of the rating for sustainable subdivision neighbourhood design (RSSND) in Bangkok Metropolitan Region (BMR), Thailand

In recent years, the problems resulting from unsustainable subdivision development have become significant problems in the Bangkok Metropolitan Region (BMR), Thailand. Numbers of government departments and agencies have tried to eliminate the problems by introducing the rating tools to encourage the higher sustainability levels of subdivision development in BMR, such as the Environmental Impact Assessment Monitoring Award (EIA-MA) and the Thai’s Rating for Energy and Environmental Sustainability of New construction and major renovation (TREES-NC). However, the EIA-MA has included the neighbourhood designs in the assessment criteria, but this requirement applies to large projects only. Meanwhile, TREES-NC has focused only on large scale buildings such as condominiums, office buildings, and is not specific for subdivision neighbourhood designs. Recently, the new rating tool named “Rating for Subdivision Neighbourhood Sustainability Design (RSNSD)” has been developed. Therefore, the validation process of RSNSD is still required. This paper aims to validate the new rating tool for subdivision neighbourhood design in BMR. The RSNSD has been validated by applying the rating tool to eight case study subdivisions. The result of RSNSD by data generated through surveying subdivisions will be compared to the existing results from the EIA-MA. The selected cases include of one “Excellent Award”, two “Very Good Award”, and five non-rated subdivision developments. This paper expects to prove the credibility of RSNSD before introducing to the real subdivision development practises. The RSNSD could be useful to encourage higher sustainability subdivision design level, and then protect the problems from further subdivision development in BMR

Land subdivision: A case study in metropolýtan area of Istanbul

The application of detailed urban plans is only possible by realizing subdivision in urban areas. Minor subdivisions, land readjustment projects and expropriations in Turkey are primary methods in realizing subdivision of urban areas. Municipalities are responsible for the application of detailed urban plans. In metropolitan areas this power is given to sub-municipalities. The purpose of this paper is to determine whether or not to be difference in realizing of subdivision according to detailed urban plans between urban areas in Istanbul Metropolitan Area. The other purpose of this paper is to constitute a model concerning realizing of subdivision according to detailed urban planning for urban areas in different population groups in Istanbul Metropolitan Area and then to compare each these city groups. For this research a sample survey method were used were questionnaires were sent to Municipalities of urban areas in different population groups in Istanbul Metropolitan Area. In addition, the realizing of subdivision ýndex (RSI) are used as a dependent variable and population, population growth rate, global density in urban areas according to detailed plans, municipal budgets, socio-economic index, the average of land values of cities. Multiple Regression Model is used for each city groups.

Mercury in Florida Bay fish: spatial distribution of elevated concentrations and possible linkages to Everglades restoration

Health advisories are now posted in northern Florida Bay, adjacent to the Everglades, warning of high mercury concentrations in some species of gamefish. Highest concentrations of mercury in both forage fish and gamefish have been measured in the northeastern corner of Florida Bay, adjacent to the dominant freshwater inflows from the Everglades. Thirty percent of spotted seatrout (Cynoscion nebulosus Cuvier, 1830) analyzed exceeded Florida’s no consumption level of 1.5 μg g−1 mercury in this area. We hypothesized that freshwater draining the Everglades served as the major source of methylmercury entering the food web supporting gamefish. A lack of correlation between mercury concentrations and salinity did not support this hypothesis, although enhanced bioavailability of methylmercury is possible as freshwater is diluted with estuarine water. Stable isotopes of carbon, nitrogen, and sulfur were measured in fish to elucidate the shared pathways of methylmercury and nutrient elements through the food web. These data support a benthic source of both methylmercury and nutrient elements to gamefish within the eastern bay, as opposed to a dominant watershed source. Ecological characteristics of the eastern bay, including active redox cycling in near-surface sediments without excessive sulfide production are hypothesized to promote methylmercury formation and bioaccumulation in the benthos. Methylmercury may then accumulate in gamefish through a food web supported by benthic microalgae, detritus, pink shrimp (Farfantepenaeus duorarum Burkenroad, 1939), and other epibenthic feeders. Uncertainty remains as to the relative importance of watershed imports of methylmercury from the Everglades and in situ production in the bay, an uncertainty that needs resolution if the effects of Everglades restoration on mercury levels in fish are to be modeled and managed

Making Markets for Development Rights Work: What Determines Demand

Many economists see current land use patterns as inefficient due to various market failures, and planners argue that current patterns do not follow sound planning practice. One policy of interest to both groups is transferable development rights (TDR). TDRs allow the development rights from land that is preserved in an undeveloped state to be transferred to other areas where development can be made denser. This paper addresses one of the greatest difficulties TDR programs face—insufficient demand. We develop a simple theoretical model and estimate a TDR demand function using data from Calvert County, Maryland, one of the only regions where data on individual sales are available. We find that baseline zoning is a critical determinant of TDR demand—demand is high in low-density rural areas but not in the relatively high-density residential areas. We also identify many subdivision characteristics that are significant in explaining TDR use.TDRs, density, zoning, subdivisions