This paper presents the reasons for uncontrolled land-use changes in the water resource basins of Istanbul. These changes are evaluated with a Geographical Information System (GIS), using four Landsat (1990, 1995, 2000, 2005) satellite images. Additional spatial information about capital improvement projects (highways and the Bosporus bridges), industrial land-use decisions, land ownership, and jurisdictional boundaries is also utilized. We observe that the most critical land-use changes have occurred in places with higher accessibility, mostly in close proximity to the metropolitan city center. The literature describes large public capital improvement projects (primarily the Trans European Motorway - TEM) as the primary reason for a trend of illegal occupation of public lands; however, the TEM should not be considered as the sole reason. This study explores other possible causes for these illegal developments in the water resource basins, grouped into three broad dimensions physical, socio-economic-political, and legal. Finally, we put forward possible policy suggestions for the preservation of the limited surface water resource basins in Istanbul. © 2008 Elsevier Ltd. All rights reserved.