Put a more reasonable default value to the number of rivers to be followed.

Interface.py

@@ -30,7 +30,7 @@ config = configparser.ConfigParser()
 config.read("run.def")
 gendoc = config.get("OverAll", "Documentation", fallback='false')
 nbxmax = config.getint("OverAll", "nbxmax", fallback=63)
-largest_pos = config.getint("OverAll", "ROUTING_RIVERS", fallback=50)
+largest_pos = config.getint("OverAll", "ROUTING_RIVERS", fallback=200)
 #
 undef_int = 999999999.9
 # Order of magnitude for the area precision in m^2.