MOISGRAD - Hyperspectrale teledetectie van vochtgradiënten: de invloed van infiltratie- en kwelgebieden

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Context and objectives

The background of this project is the importance of the determining and describing hydrological groundwater systems for the management and development of ecological values, especially in valleys of the river basin. At the ground surface, groundwater systems appear as infiltration and discharge zones; the latter are relatively wet because of the upward groundwater seepage, while the former are relatively dry. The main objective of this project is to try out the best hyperspectral analysis method, using the CASI-SWIR data, for the known (based upon field and simulation data) moisture gradients in the Doode Bemde area in the valley of the Dijle River. An advantage of this study area is that it was the object of study of extensive hydro-ecological research during the last five years, for which a lot of field measurements as well as simulations have been carried out. This area is also very suited because of the hydro-chemical uniformity and clear, relatively constant, moisture gradients and associated differences in vegetation on a small scale caused by groundwater flow differences.

Project outcome

Expected scientific results

For soil moisture the best results (correlation: -0,69) were obtained for the individual bands with wavelengths between 0,5240 μm and 0,5800 μm. A normalisation of band 26 (0,5690 μm) gave the best correlation (-0.73). Correlation with groundwater depth runs parallel with the soil moisture but at a lower level. A maximum correlation of 0.46 was found for band 77 (0,8610 μm). Indices or ratios did not (yet?) give better results in both cases. Based on these results a classification of wetter and dryer zones was possible. The hyperspectral dataset was also used to create a detailed land use map for the study area. Housing and infrastructure, water bodies, forest, grasslands (cut/uncut), etc. could be determined. 85% of the classified Phragmites australis appears to be located in the field mapped zone of Phragmites australis. Of the correctly classified Phragmites australis 83% occurs in a zone where the abundance of Phragmites australis is estimated in the field as 75-100%. This indicates that high abundance occurrence of Phragmites australis can be mapped relatively well if it is the major high abundance specie occurring. This is illustrated by the fact that for some parts of the zones where Phragmites australisarea occur with high abundance, Phalaris arundinacea and Filipendula ulmaria also have a high abundance, here Phragmites australis was not correctly classified due to the non-purity of the pixels.