[ 2004 
NATURAL ENVIRONMENT CHANGE DETECTION IN DANUBE DELTA, 
BASED ON HRV - SPOT IMAGES 
I. Ionescu, I. Noaje 
Geodetic and Photogrammetric Department, Technical University of Civil Engineering Bucharest, 
Bd. Lacul Tei 124, Sect 2, , Bucharest , Cod 020396, O.P. 38, ROMANIA 
e-mail: ionescu_ion_1946@yahoo.com: noaje@pcnet.ro 
Working Group VII / 5 
KEY WORDS: Environment, Geomorphology, Change detection, Monitoring, Registration 
ABSTRACT: 
The Danube Delta is an area with a unique ecological signification, which present accentuated interest from scientific, tourist and 
even economically. His complex and varieties ecosystems have rem 
ained unspoiled for centuries, natives integrating in preserving of 
natural balance. In the last 3-4 decades, a dramatic alteration be cause of accentuated human intervention in Danube area, inside 
Danube Delta's and in coastal area.of Black Sea. 
In this context, a study on change-detection occurred at the level of principal morphological elements and vegetation has been 
achieved in a site, which contain approximate 70% of delta’s surface. The study is based on two HRV SPOT images, acquired in 
May 27, 1986 and April 27, 1993. 
Two different methods have been used for change detection: vegetation index comparison and post-classification achieved based on 
the composite images. A Normalized Difference Vegetation Index (NDVI) has been computed for each image; then the new images 
have been compared by difference in first case. Using the second method, composite images are generated from the two principal 
components on which are added Normalized Difference Vegetation Index (NDVI). Furthermore, these images are submitted a hybrid 
classification process, followed by a modal type filtering. Finally, the classified and filtered images are compared by difference. 
The study first revealed the utility of HRV SPOT images for delta’s environment monitoring. Between two methods used, more 
accurately results give comparison post classification of composite images. The accuracy is improved significantly if the threshold 
value of mode filters is choused according. 
1. INTRODUCTION 
After declaring in august 1990 of the Danube Delta's as 
Biosphere Reserve, on passed at effecting a couple of projects 
of national and international research having as main purpose, 
establishing the solutions for protection and ecological 
reconstruction of nature delta's environment. In this context, a 
study on change-detection occurred at the level of principal 
morphological elements and vegetation has been achieved. The 
study of environments and change-detection require using of 
the efficiency evaluation methods. The remote sensing offer 
one global view of phenomenon and is in same time the 
privileged study means, which can facilitated the best 
environment administrations. 
2. STUDY ZONE AND DATA SOURCE 
The Danube Delta and the coastal zone of the Black Sea 
represent areas of high scientific interest, which contain a 
unique series of interrelated ecosystems. This cover about 
564,000 ha of which 442,000 ha (82%) lie within Romania. 
Inside the delta some main ecosystems are to be found among 
which we can mention: running water, stagnant water, wetland 
763 
and flooded areas, fluvial and marine levees, the amended areas 
(for agriculture, forestry and fish culture). 
Ecosystem of running waters comprises in the first place the 
Danube's arms, bat also a series of more important streamlets 
and channels. 
Ecosystem of stagnant waters includes in the first place lakes, 
to which ponds, streamlets and channels are added. They are 
characterised by a rich floating and submersed flora. 
Ecosystem of marshy and flooding surfaces (of reed plats and 
floating reed islet) is dominated by emerged vegetation 
prevalent constituted of common reed. Floating reed islet 
formation, which is a mixture of reed roots herbs and soil, 
usually floating or fixed on the bottom of depressions, has a 
peculiar place within the ecosystem. 
Fourth main ecosystem is river banks and levees ecosystem. 
This is centred on the riverbanks which had been the domain of 
all kind of trees which had been broke up in their greatest part 
and instead, Canadian poplars had been cultivated. 
Based on the HRV SPOT scenes had been realised a study of 
environments evolution in the Danube Delta. The study areas 
cover approximate 70% of delta’s surfaces. Is very important of 
underline its neighbourings in the east side with Black Sea, 
which a specifically series problems creating.