valley, isolating the glacier covering Bas-Saint-Laurent from the one covering Côte-Nord. The isostatic rebound created an inland sea, the Sea of Goldthwait, which flooded the region under at most 200m of water in the area around Rimouski. The withdrawal of the Sea of Goldthwait was gradual, 2,000 years ago the isostatic rebound stabilised at around per year, the withdrawal of the water formed a number of narrow streaks of emerged land near the riverside between Rivière-du-Loup and Rimouski, known today as Île aux Lièvres, Île Verte, île aux Basques, île du Bic and île Saint-Barnabé. Hydrography The estuary of the Saint Lawrence river, to the north of the region, plays a primary role in the region. It is divided in two regions split at Cacouna: west of Cacouna, it is called a medium estuary, while east of the municipality it is called a maritime estuary or lower estuary. The region is relatively poor in fresh water, since lakes and rivers only count as 1.5% of the land area. It possesses two hydrographic regions, the first holds all the streams that pour into the estuary of the Saint-Lawrence river and the region of Chaleur Bay and Percé, whose streams flow south into New-Brunswick and Maine. These regions influenced the layout of the administrative areas of Bas-Saint-Laurent, by setting limits to some regional county municipalities. The largest drainage basins of the region are located in the south of the territory. These are the drainage basins of the Matapedia River () and Madawaska River (). Ranking third, the drainage basin of the Cascapédia River of , half of this basin is located within the limits of the administrative region. Among the notable rivers pouring into the Saint-Lawrence, we can count the Mitis River (), Matane River (), Rimouski River (), Rivière du Loup () and Trois Pistoles River (). Bas-Saint-Laurent counts 2,417 lakes, of which 90% do not exceed an area of . About 30% of them are situated in the RCM of Rimouski-Neigette. The two largest lakes of the region are Lake Témiscouata () and Lake Matapedia (), significant human settlement on their shore has taken place, as well as along the roads going through their valleys. These lakes also distinguish themselves by their north west and south west orientation, compared to most of the other lakes of the region which prefer to follow the orientation of the creases and breaks of