LANDCOVER MAPPING AND MULTICRITERIA MODELING FOR EXPLAINING THE SPATIAL AND TEMPORAL DISTRIBUTION OF A PAPYRUS SWAMP AT LAKE NAIVASHA, KENYA

摘要

This paper is an extract of a research (thesis) done on the distribution of the papyrus swamp at Lake Naivasha in 1998 by the same author. Based on area per habitat and trends as indicators, the distribution was derived from the temporal analysis of land cover maps. Remotely sensed data (aerial photographs 1967 and 1984 plus a TM satellite image of 1995) were analysed for the period 1967 to 1995 within two year sets as 1967/1984 and 1984/1995. The distribution of the swamp would be explained by the influence of its neighbour landcover. Risk potential zones represented in two model scenarios were established indicating relative influence of the landcover based on change rates and distance as criteria. The criteria evaluation was done in a Decision Support System and results combined spatially in a GIS. The papyrus area declined at a rate of 71percent between 1967 and 1995. The major influence and risk to the swamp area in order of magnitude were open water, shrubland, agricultural area, woodland, grassland and built up area. The integration of climatic regime, ground water level, soil drainage/depth, topography and anthropogenic factors as grazing and burning should be considered for improved explanations.