Detailed Land Cover Map Research Articles

Soil erosion modelled with USLE and PESERA using QuickBird derived vegetation parameters in an alpine catchment

The focus of soil erosion research in the Alps has been in two categories: (i) on-site measurements, which are rather small scale point measurements on selected plots often constrained to irrigation experiments or (ii) off-site quantification of sediment delivery at the outlet of the catchment. Results of both categories pointed towards the importance of an intact vegetation cover to prevent soil loss. With the recent availability of high-resolution satellites such as IKONOS and QuickBird options for detecting and monitoring vegetation parameters in heterogeneous terrain have increased. The aim of this study is to evaluate the usefulness of QuickBird derived vegetation parameters in soil erosion models for alpine sites by comparison to Cesium-137 (Cs-137) derived soil erosion estimates. The study site (67km2) is located in the Central Swiss Alps (Urseren Valley) and is characterised by scarce forest cover and strong anthropogenic influences due to grassland farming for centuries. A fractional vegetation cover (FVC) map for grassland and detailed land-cover maps are available from linear spectral unmixing and supervised classification of QuickBird imagery. The maps were introduced to the Pan-European Soil Erosion Risk Assessment (PESERA) model as well as to the Universal Soil Loss Equation (USLE). Regarding the latter model, the FVC was indirectly incorporated by adapting the C factor. Both models show an increase in absolute soil erosion values when FVC is considered. In contrast to USLE and the Cs-137 soil erosion rates, PESERA estimates are low. For the USLE model also the spatial patterns improved and showed “hotspots” of high erosion of up to 16tha−1a−1. In conclusion field measurements of Cs-137 confirmed the improvement of soil erosion estimates using the satellite-derived vegetation data.

Comparison of pixel and sub-pixel based techniques to separate Pteronia incana invaded areas using multi-temporal high resolution imagery

Remote Sensing using high resolution imagery (HRI) is fast becoming an important tool in detailed land-cover mapping and analysis of plant species invasion. In this study, we sought to test the separability of Pteronia incana invader species by pixel content aggregation and pixel content de-convolution using multi-temporal infrared HRI. An invaded area in Eastern Cape, South Africa was flown in 2001, 2004 and 2006 and HRI of 1x1m resolution captured using a DCS 420 colour infrared camera. The images were separated into bands, geo-rectified and radiometrically corrected using Idrisi Kilimanjaro GIS. Value files were extracted from the bands in order to compare spectral values for P. incana, green vegetation and bare surfaces using the pixel based Perpendicular Vegetation Index (PVI), while Constrained Linear Spectral Unmixing (CLSU) surface endmembers were used to generate sub-pixel land surface image fractions. Spectroscopy was used to validate spectral trends identified from HRI. The PVI successfully separated the multi-temporal imagery surfaces and was consistent with the unmixed surface image fractions from CLSU. Separability between the respective surfaces was also achieved using reflectance measurements.

Are there habitats that contribute best to plant species diversity in coastal dunes?

The following paper describes patterns of diversity across major habitat types in a relatively well preserved coastal dune system in central Italy. The research addresses the following questions: (a) whether different habitats defined on the base of a land cover map support similar levels of biodiversity in terms of vascular flora richness and number of rare and endangered species, and (b) how each habitat contributes to the total species diversity of the coastal environment. A random stratified sampling approach based on a detailed land cover map was applied to construct rarefaction curves for each habitat type and to estimate total species richness. In addition, the number of exclusive, rare and endangered species was calculated for each habitat type. Results highlight the importance of the coastal dune zonation (embryo-dune, main dune, transition and stabilized dune) in species conservation because they harbour progressively higher species richness. However, differences among these habitats were not significant, so no particular species rich “hotspots” could be evidenced. On the contrary, rarefaction curves show that the upper beach (strand) habitat sustains significantly smaller number of species, but surprisingly, it shows the highest rarity values and highest proportion of endangered species. Therefore, for the establishment of successful biodiversity conservation programs in these coastal environments, it is imperative not only to conserve biologically rich hotspots but also to include species poor habitats containing endangered or unique elements. Thus, the complete coastal vegetation mosaic including all coastal habitats is important to adequately characterize the plant species diversity of coastal dune ecosystems.

Urban sprawl in the Mediterranean?: Patterns of growth and change in the Barcelona Metropolitan Region 1993–2000

Debates on the urban form have become strongly polarized between the advocates and opponents of the compact and of the dispersed or “sprawled” city. In this paper we argue that this may be the result of an excessive concentration on the study of the American experience and the neglect of other urban contexts, and examine the recent process of urban growth against the background of urban compactness and extreme densification represented by the Barcelona Metropolitan Region (BMR). The comparison of two detailed land-cover maps of 1993 and 2000 shows a progressive transformation in the traditional urban character of the region. Lower urban densities, high losses of non-urban land covers, depopulation of the metropolitan inner core, an increasing importance of single housing or the expansion of transportation infrastructures confirm the generalization of the dispersed urban model. However, the presence of numerous medium sized towns has also proved to be a deterrent of excessive dispersion. In conclusion, polycentric metropolitan areas such as the BMR may be more adjusted to absorb the negative effects of dispersion than monocentric areas.

A landscape approach for assessing the biodiversity value of indigenous forest remnants: Case study of the Manawatu/Wanganui region of New Zealand

To halt the decline of biodiversity in New Zealand, the government has formulated a strategy of maintaining and restoring a full range of remaining natural habitats to a healthy functioning state. Many indigenous forest remnants exist on private land, and these could be utilised to increase biodiversity. Resources for conservation of forest remnants are limited, so they must be used wisely to deliver the greatest possible biodiversity gain. This paper presents a rapid method for valuing the biodiversity of a region's indigenous forest remnants to help prioritise conservation resources. The region is divided into environmentally distinct areas called land environments. A detailed land-cover map is derived from satellite imagery and used to estimate the proportion of natural habitats remaining in each land environment; from this the biodiversity value of any forest remnant may be calculated. The method is rapid and does not require detailed biodiversity information. When combined with conservation costs, it may be used to create a priority list of forest remnants for conservation. The Manawatu/Wanganui region of New Zealand is used as a case study to demonstrate the method.

Planning restoration in a cultural landscape in Italy using an object-based approach and historical analysis

We present a proposal for a standardized method to develop restoration practices capable of increasing the efficacy of landscape management and create the necessary bridge between restoration planning and landscape ecology. This methodology was developed in order to identify the reference landscape and to define areas within that landscape that possess different degrees of potential for restoration purposes in a cultural landscape. We utilized retrospective data to compare former ecosystem arrangements, taking into account ecological, spatial and temporal issues, such as historical information on changes in land use, in addition to diachronically analyzed aerial photos taken between 1954 and 2002, using an object-based approach. The test area is a Nature Reserve in Tuscany (Italy) that preserves the cultural landscape of biancane badlands – erosion forms generated on Plio-Pleistocene marine clay outcrops – which is characterized by a high erosion rate. In the first step, a land cover map was obtained by image segmentation on the 1954 photographs and the patches classified as “target habitats” were used as a selection mask on the 2002 image. As a second step, a more detailed land cover map was created for the areas selected as masks in the previous step. Hence, the target habitats that showed stability (persistence) between the two dates were excluded from the analysis, as well as the land cover classes not suitable for restoration (broad-leaved forests, arable land, artificial and other agricultural areas). The selected sites, covered by four vegetation types in the 2002 land cover map, accounted for approximately 91 ha. The method focuses on selecting sites for restoration in order to reduce efforts and negative impact and to maximize the restoration results.

Fine-resolution remote-sensing and modelling of Himalayan catchment sustainability

A number of studies have reported on environmental degradation in the Nepal Himalaya as a result of large-scale deforestation and the associated agricultural extension. In contrast to many previous regional scale studies, we consider land cover and its environmental impact on an individual catchment-scale, using fine-resolution Quickbird data and a soil erosion model. First, using a detailed land cover map generated from Quickbird imagery, we establish basic relationships between land cover, dwelling density and topographic variability, which exist in a typical mid-elevation Nepalese catchment, the Pokhare Khola. These data suggest a strongly subsistence type of household economy based predominantly on terraced arable farming. We demonstrate using multitemporal vegetation indices that this farmland has existed in the region since the late 1980s, and that widespread deforestation has not taken place since then, possibly as a result of specific forest conservation policies of the government coupled with efforts by local communities. Further, through the use of soil erosion modelling we demonstrate the role that the terraced farming practices can play in reducing runoff and hence soil nutrient loss, thereby enabling restoration of vegetation in the previously deforested land terrains. Finally, by combining this information with regional land cover data, we show that the findings of this research can be scaled up to draw conclusions about environmental degradation across the Nepal Himalayan region.

Modeling potential species richness and urban buildout to identify mitigation sites along a California highway

One-foot resolution imagery is used to develop a detailed land cover map for part of Highway 99 in the San Joaquin Valley of California, US. The land cover map is used to model the probability of occurrence of 12 endangered or threatened species and as input to an urban growth model to examine the likelihood of development of every map unit. The combination of the two model predictions permits the categorization of every map unit with a potential endangered species richness index and predicted degree of development. Polygons with high potential endangered species richness were ranked according to the degree of development pressure. This planning approach is computationally intensive, but the input data are relatively easy to assemble, consisting of: a detailed, and fine-scale, land cover map; species presence locations; state-wide climate and landcover maps; a parcel ownership map; population growth projections; and a digital map of the county general plan.

Airborne laser scanning and usefulness for hydrological models

Abstract. Digital terrain models form the basis for distributed hydrologic models as well as for two-dimensional hydraulic river flood models. The technique used for generating high accuracy digital terrain models has shifted from stereoscopic aerial-photography to airborne laser scanning during the last years. Since the disastrous floods 2002 in Austria, large airborne laser-scanning flight campaigns have been carried out for several river basins. Additionally to the topographic information, laser scanner data offer also the possibility to estimate object heights (vegetation, buildings). Detailed land cover maps can be derived in conjunction with the complementary information provided by high-resolution colour-infrared orthophotos. As already shown in several studies, the potential of airborne laser scanning to provide data for hydrologic/hydraulic applications is high. These studies were mostly constraint to small test sites. To overcome this spatial limitation, the current paper summarises the experiences to process airborne laser scanner data for large mountainous regions, thereby demonstrating the applicability of this technique in real-world hydrological applications.

Impacts of reforestation and gravel mining on the Malnant River, Haute-Savoie, French Alps

The Malnant River is a rapidly incising river with a French name that translates as “bad creek,” reflecting local opinion of the hazards from dramatic channel changes that have occurred in the last few centuries. Downcutting in the last three decades has created severe problems for farmers in this small watershed (16 km 2) as bridges are undermined, streamside roads are threatened, and irrigation diversion structures are rendered unusable. The purpose of our study was to determine the extent and causes of downcutting. A detailed landcover map dated 1732 revealed that forest cover had been reduced by that time to 10% of the present-day cover. The Malnant was strongly affected by floods and debris torrents during the 18th and 19th centuries that delivered massive amounts of sediment. During the 20th century, reforestation reduced the sediment delivery from hillslopes. In addition, gravel extraction in the Malnant and in the Fier River (of which the Malnant is a tributary) has lowered the base level for the river. This initiated a knickpoint that moved upstream. Weirs placed in the Malnant in 1968 were used to measure rates of bed incision in the field. With a mean width of 4.0 m and degradation up to 36 cubic meters per meter channel length, the lower 4.5 km of the Malnant has experienced a net loss of approximately 163,000 m 3 of bed material. Above the 4.5-km point on the Malnant, bedrock controls exist that have arrested the upstream-progressing degradation.

A segmentation and classification approach of IKONOS-2 imagery for land cover mapping to assist flood risk and flood damage assessment

Various regions in Europe have suffered from severe flooding over the last decennium. Earth observation techniques can contribute toward more accurate flood hazard modelling and they can be used to assess damage to residential properties, infrastructure and agricultural crops. For this study, detailed land cover maps were created by using IKONOS-2 high spatial resolution satellite imagery. The IKONOS-2 image was first divided into segments and the land cover was classified by using spectral, spatial and contextual information with an overall classification accuracy of 74%. In spite of the high spatial resolution of the image, classes such as residential areas and roads are still fairly difficult to identify. The IKONOS-2-derived land cover map was used as input for the flood simulation model LISFLOOD-FP to produce a Manning roughness factor map of inundated areas. This map provides a more accurate spatial distribution of Manning’s roughness factor than maps derived from land cover datasets such as the EU CORINE land cover dataset. CORINE-derived roughness maps provide only averaged, lumped values of roughness factors for each mapping unit and are hence less accurate. Next, a method to produce a property damage map after flooding is presented. The detailed land cover map, water depth estimates resulting from the LISFLOOD-FP model, and known relations between water depth and property damage yielded a map of estimated property damage for the 1995 flood which affected the villages of Itteren and Borgharen in the southern part of The Netherlands. Such a map is useful information for decision makers and insurance companies.

Improved urban land cover mapping using multi-temporal IKONOS images for local government planning

This paper studies the potential role of multi-temporal (leaves-on ‐ spring and leaves-off ‐ fall) and multi-spectral IKONOS satellite images in the development of detailed and accurate urban land cover maps to assist planners and managers in the rapidly growing city of Columbia, Missouri, U.S.A. To improve the overall accuracy of the urban land cover map, multi-temporal images were classified separately and then outputs were combined. The result produced from the combined outputs was an improvement over the previous single season image. An up-to-date and detailed land cover map produced from these images can help planners in developing better urban land use plans. This paper also discusses in detail the problems encountered and lessons learned in using high-resolution satellite images in urban land cover classification so as to help planners proposing to use similar type images in future.

Landcover changes and δ13C composition of riverine particulate organic matter in the piracicaba river basin (southeast region of brazil)

Assuming the paradigm that catchment vegetation is the main source of particulate organic matter (POM) to rivers, the main objective of this study was to determine what the proportion of original C3 carbon from the forest had already been replaced by C4 carbon from sugar cane and pasture in the rivers of the Piracicaba Basin. In order to achieve this objective, we first produced a detailed landcover map using Landsat5‐TM images, and then we measured the carbon stable isotopic composition of the particulate riverine organic matter (δ13C‐POM) in seven sites along the major rivers and in two sites along a small creek. Sugar cane and pasture (C4 plants) covered almost 60% of the basin area, while silviculture, mostly of other crops, citrus, and forest that are C3 plants, covered 35%. Isotopic studies conducted in large pristine tropical rivers of South America and of Africa have shown that catchment vegetation is the main source of carbon in suspended POM. Our study demonstrates that relatively recent changes (70–80 yr ago) in landcover in the Piracicaba River Basin have already affected the composition of the riverine POM. Therefore, as in natural ecosystems, the vegetation (allochthonous source) plays an important role in the composition of the riverine POM in agricultural systems such as the Piracicaba River Basin. This control can be supported by the good correlation between cumulative area of the basin covered with C4 plants and the δ13C of the riverine POM. However, our study, differently from others, also shows that, during the low water period, in situ processes, such as primary production, may be an important source of carbon to the riverine POM.

Accuracy assessment in cotton acreage estimation using Indian remote sensing satellite data

The accuracy of cotton crop classification using satellite data has been assessed with respect to a detailed land cover map prepared by field survey. The effect of spatial resolution on classification accuracy was studied using LISS-I (spatial resolution 72.6 m) and LISS-II data (spatial resolution 36.25 m) of the Indian remote sensing satellite IRS-1B. The performances of the maximum likelihood and the minimum distance to mean as classifiers have also been assessed. LISS-II data have been found to give a higher classification accuracy. The estimate of cotton acreage using LISS-II data was closer to that obtained from the base map. The maximum likelihood classifier (MXL) and the minimum distance to mean (MDM) classifier performed equally well.