This study presents an application of a multiple point geostatistics (MPS) to map landforms. MPS uses information at multiple cell locations including morphometric attributes at a target mapping cell, i.e. digital elevation model (DEM) derivatives, and non-morphometric attributes, i.e. landforms at the neighboring cells, to determine the landform. The technique requires a training data set, consisting of a field map of landforms and a DEM. Mapping landforms proceeds in two main steps. First, the number of cells per landform class, associated with a set of observed attributes discretized into classes (e.g. slope class), is retrieved from the training image and stored in a frequency tree, which is a hierarchical database. Second, the algorithm visits the non-mapped cells and assigns to these a realization of a landform class, based on the probability function of landforms conditioned to the observed attributes as retrieved from the frequency tree. The approach was tested using a data set for the Buëch catchment in the French Alps. We used four morphometric attributes extracted from a 37.5-m resolution DEM as well as two non-morphometric attributes observed in the neighborhood. The training data set was taken from multiple locations, covering 10% of the total area. The mapping was performed in a stochastic framework, in which 35 map realizations were generated and used to derive the probabilistic map of landforms. Based on this configuration, the technique yielded a map with 51.2% of correct cells, evaluated against the field map of landforms. The mapping accuracy is relatively high at high elevations, compared to the mid-slope and low-lying areas. Debris slope was mapped with the highest accuracy, while MPS shows a low capability in mapping hogback and glacis. The mapping accuracy is highest for training areas with a size of 7.5-10% of the total area. Reducing the size of the training images resulted in a decreased mapping quality, as the frequency database only represents local characteristics of landforms that are not representative for the remaining area. MPS outperforms a rulebased technique that only uses the morphometric attributes at the target mapping cell in the classification (i.e. one-point statistics technique), by 15% of cell accuracy.
The river carries a very high load of SO4, NH4, PO4, Cl, F, Fe, Cu, Pb, Zn, Al and other potentially toxic elements. Precipitation and discharge data over the period of 1980-2000 clearly show that the precipitation on the Ijen plateau influences water chemistry of the downstream river. Metal concentrations in the river water exceed the concentrations mentioned in Indonesian and international quality guidelines, even in the downstream river and the irrigation area. Some metal concentrations are extremely high, especially iron (up to 1,600 mg/l) and aluminium (up to 3,000 mg/l). The food-webs in the acidic parts of the river are highly underdeveloped. No invertebrates were present in the extremely acidic water and, at pH 2.3, only chironomids were found. This also holds true for the river water with pH 3.3 in the downstream area. Agricultural soils in the irrigation area have a pH of 3.9 compared to a pH of 7.0 for soils irrigated with neutral water. Decreased yields of cultivated crops are probably caused by the use of Al containing acidic irrigation water. Increased levels of metals (especially Cd, Co, Ni and Mn) are found in different foodstuffs, but still remain within acceptable ranges. Considering local residents' diets, Cd levels may lead to an increased risk for the human health. Fluoride exposure is of highest concern, with levels in drinking water exceeding guideline values and a lot of local residents suffering from dental fluorosis. CONCLUSIONS, RECOMMENDATIONS AND OUTLOOK: In short, our data indicate that the Ijen crater lake presents a serious threat to the environment as well as human health and agricultural production.
For a large part of the year, the forested catchments in the Keuper formation of east Luxembourg produce more direct run-off on a storm basis than paired cultivated catchments. The occurrence of shrinkage cracks, their pronounced opening and closing, and the occurrence of natural pipes in the forested environment play a major role in explaining this phenomenon. The effect of land use on storm run-off is studied in relation to that found for lithology in the same area.KEY WORDS Direct run-off Land use Shrinkage cracks Natural pipes OBJECTIVESThe objectives of this study were (1) to establish the relative quantitative effects of lithology and land use on storm run-off for small catchments in east Luxembourg, and (2) to relate these effects to dynamic hydrological processes observed in the field. EXPERIMENTAL DESIGNA network for measuring rainfall and discharge was designed and established in April 1984 within the Keuper marls and Luxembourg sandstone formation. Precipitation was measured at four sites with Siap tipping bucket recorders mounted 60 cm above ground level, and discharge was measured at six sites using 90" V-notch weirs (Thomson weirs), equipped with either Seba or Leopold and Stevens stage recorders (Figure 1). The catchments were visited at least monthly for 18 months. STUDY AREAForested soils in the Keuper marls are characterized by many large biopores and natural pipes in the surface soil caused by the combined action of root decay and the activity of earthworms, voles and moles, and by a clayey B-horizon at approximately 30 cm, causing a rapid decrease in vertical profile permeability. The Keuper soils under cultivation or pasture differ from those under forest in being truncated to the lower B-or C-horizons. The weathering product of the Luxembourg sandstone, in contrast, is a permeable loamy sand. Information on lithostratigraphy and land use for the studied catchments are presented in Table I and Figure 2. A full description of the fieldwork area is presented in Hendriks (1990). HYDROMORPHOMETRIC DATAAs run-off data are highly correlated with catchment physiography (NERC, 1975), catchment values for a number of hydromorphometricai variables were determined.
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