Transferring Google Earth observations to GIS-software : example from gully erosion study

High-resolution images available on Google Earth are increasingly being consulted in geographic studies. However, most studies limit themselves to visualizations or on-screen measurements. Google Earth allows users to create points, lines, and polygons on-screen, which can be saved as Keyhole Markup Language (KML) files. Here, the use of R statistics freeware is proposed to easily convert these files to the shapefile format [or .shp file format'], which can be loaded into Geographic Information System (GIS) software (ESRI ArcGIS 9 in our example). The geospatial data integration in GIS strongly increases the analysis possibilities

Assessing spatio-temporal rainfall variability in a tropical mountain area (Ethiopia) using NOAA's rainfall estimates

Seasonal and interannual variation in rainfall can cause massive economic loss for farmers and pastoralists, not only because of deficient total rainfall amounts but also because of long dry spells within the rainy season. The semi-arid to sub-humid mountain climate of the North Ethiopian Highlands is especially vulnerable to rainfall anomalies. In this article, spatio-temporal rainfall patterns are analysed on a regional scale in the North Ethiopian Highlands using satellite-derived rainfall estimates (RFEs). To counter the weak correlation in the dry season, only the rainy season rainfall from March till September is used, responsible for approximately 91% of the annual rainfall. Validation analysis demonstrates that the RFEs are well correlated with the meteorological station (MS) rainfall data, i.e. 85% for RFE 1.0 (1996-2000) and 80% for RFE 2.0 (2001-2006). However, discrepancies indicate that RFEs generally underestimate MS rainfall and the scatter around the trendlines indicates that the estimation by RFEs can be in gross error. A local calibration of RFE with rain gauge information is validated as a technique to improve RFEs for a regional mountainous study area. Slope gradient, slope aspect, and elevation have no added value in the calibration of the RFEs. The estimation of monthly rainfall using this calibration model improved on average by 8%. Based upon the calibration model, annual rainfall maps and an average isohyet map for the period 1996-2006 were constructed. The maps show a general northeast-southwest gradient of increasing rainfall in the study area and a sharp east-west gradient in its northern part. Slope gradient, slope aspect, elevation, easting, and northing were evaluated as explanatory factors for the spatial variability of annual rainfall in a stepwise multiple regression with the calibrated average of RFE 1.0 as dependent variable. Easting and northing are the only significant contributing variables (R-2=0.86), of which easting has proved to be the most important factor (R-2=0.72). The scatter around the individual trendlines of easting and northing corresponds to an increase in rainfall variability in the drier regions. Despite the remaining underestimation of rainfall in the southern part of the study area, the improved estimation of spatio-temporal rainfall variability in a mountainous region by RFEs is valuable as input to a wide range of scientific models

Spatio-temporal modeling of soil characteristics for soilscape reconstruction

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On the use of integrated process-models to reconstruct prehistoric occupation wiht examples from Sandy Flanders (Belgium)

Reconstructing palaeolandscapes is challenging because of the limited amount of basic useable data, which often have a scattered temporal and geographical distribution. In order to obtain a continuous image of past landscapes, methods are required to interpolate landscape characteristics in both space and time. To improve the understanding of observed distributions of pre- and protohistoric sites in Flanders (Belgium) by means of a landscape reconstruction, the application of different process-models in the soil-water-landscape in an interdisciplinary approach is proposed. These process-models include a digital elevation model (cf. Werbrouck I. et al.), a hydrological model, a pedogenesis model and a land evaluation model. Due to the multiple disciplines involved, no single model can be used but a model framework is defined in which the various discipline-specific models are integrated. All of these models are interconnected: the output of one model is used as an input to another model. This implies that when integrating these different models certain considerations have to be made concerning grain, extent and coverage. The model framework is being constructed and tested for the area of Sandy Flanders, a relatively flat and low-lying area situated at the southern border of the cover sand region of the NW European plain. This is one of the most intensively archaeologically surveyed areas of NW Europe. Numerous, generally small and elongated sand dunes, shallow mires and wet depressions were formed during the Late Pleniglacial and the Late Glacial. One of these palaeolakes, the Depression of the Moervaart, was ca. 15 km long and 2,5km wide and has an infilling of lake marl, alternated with peat. Next to the model framework, this project on site distribution in Sandy Flanders also covers intense field surveys, archaeological as well as palaeoecological and geomorphological (cf. De Reu J. et al.)

A methodology for the reconstruction of palaeogroundwater regimes in Sandy Flanders throughout the Holocene and the Late Glacial.

During the last three decades intense archaeological prospection has taken place in the region of Sandy Flanders (Belgium). This has led to the production of archaeological distribution maps, which show a distinct pattern regarding the temporal and spatial distribution of these archaeological sites. Besides human factors, environmental conditions such as topography, hydrology, climate, soil and vegetation need to be examined in order to determine and explain the occupational history of the region. In this area with shallow groundwater tables, environmental processes such as pedogenesis and vegetation development are strongly influenced by the groundwater table dynamics. Since the palynological record only provides scattered information on palaeo-groundwater depths, a groundwater modeling is necessary in order to obtain full-cover maps of the groundwater regime. Therefore, we propose a new methodology for palaeo-groundwater modeling over large temporal extents (15000 years), which is based on the modflow-model MOCDENS3D. In a first stage, we simulate groundwater heads over the area for time-windows of 30 years (i.e. a climatic period). For each time-window a topographical and drainage pattern reconstruction is regarded together with the climatic data for that specific period. Intervals between the time-windows vary in length, depending on the amount of time between large topographical changes in the study area. This first stage allows the calculation of a spatially full-cover set of monthly palaeo-groundwater tables for different time-windows. In order to obtain a continuous set of the groundwater heads for the entire temporal extent of this investigation, mathematical spatio-temporal methods will be applied to interpolate between the simulated palaeo-groundwater heads of each time-window. This will be done in a second stage of this investigation. Ultimately, the model will be calibrated with a set of phreatic groundwater depths derived from palynological analysis