INSTITUTE OF GEOGRAPHY AND SPATIAL DEVELOPMENT OF THE POLISH ACADEMY OF SCIENCES IM. STANISŁAW LESZCZYCKI Department of Geomorphology and Hydrology of the Lowlands 87-100 Toruń, Kopernika 19 phone: + 48 + 56 6228520 FAX: + 48 + 56 6210388 e-mail: sekret@geopan.torun.pl