diff --git a/heightmap.lua b/heightmap.lua
index cbe8923..d6b2303 100644
--- a/heightmap.lua
+++ b/heightmap.lua
@@ -6,7 +6,7 @@ local transform_quadri = dofile(modpath .. 'geometry.lua')
 local sea_level = mapgen_rivers.settings.sea_level
 local riverbed_slope = mapgen_rivers.settings.riverbed_slope * mapgen_rivers.settings.blocksize
 
-local MAP_BOTTOM = -31000
+local out_elev = mapgen_rivers.settings.margin_elev
 
 -- Localize for performance
 local floor, min, max = math.floor, math.min, math.max
@@ -128,8 +128,8 @@ local function heightmaps(minp, maxp)
 				terrain_height_map[i] = terrain_height
 				lake_height_map[i] = lake_height
 			else
-				terrain_height_map[i] = MAP_BOTTOM
-				lake_height_map[i] = MAP_BOTTOM
+				terrain_height_map[i] = out_elev
+				lake_height_map[i] = out_elev
 			end
 			i = i + 1
 		end
diff --git a/pregenerate.lua b/pregenerate.lua
index 91fac15..164d2ad 100644
--- a/pregenerate.lua
+++ b/pregenerate.lua
@@ -13,9 +13,9 @@ local time_step = mapgen_rivers.settings.evol_time_step
 local niter = math.ceil(time/time_step)
 time_step = time / niter
 
-local use_margin = true
-local margin_width = 2000 / blocksize
-local margin_elev = -200
+local use_margin = mapgen_rivers.settings.margin
+local margin_width = mapgen_rivers.settings.margin_width / blocksize
+local margin_elev = mapgen_rivers.settings.margin_elev
 
 local function margin(dem, width, elev)
 	local X, Y = dem.X, dem.Y
diff --git a/settings.lua b/settings.lua
index 87f26fd..5eef795 100644
--- a/settings.lua
+++ b/settings.lua
@@ -74,6 +74,9 @@ mapgen_rivers.settings = {
 
 	grid_x_size = def_setting('grid_x_size', 'number', 1000),
 	grid_z_size = def_setting('grid_z_size', 'number', 1000),
+	margin = def_setting('margin', 'bool', true),
+	margin_width = def_setting('margin_width', 'number', 2000),
+	margin_elev = def_setting('margin_elev', 'number', -200),
 	evol_params = {
 		K = def_setting('river_erosion_coef', 'number', 0.5),
 		m = def_setting('river_erosion_power', 'number', 0.4),
diff --git a/settingtypes.txt b/settingtypes.txt
index 455a6b0..7d266e9 100644
--- a/settingtypes.txt
+++ b/settingtypes.txt
@@ -17,6 +17,16 @@ mapgen_rivers_grid_x_size (Grid X size) int 1000 50 5000
 #    Actual size of the map is grid_z_size * blocksize
 mapgen_rivers_grid_z_size (Grid Z size) int 1000 50 5000
 
+#    If margin is enabled, elevation becomes closer to a fixed value when approaching
+#    the edges of the map.
+mapgen_rivers_margin (Margin) bool true
+
+#    Width of the transition at map borders, in nodes
+mapgen_rivers_margin_width (Margin width) float 2000.0 0.0 15000.0
+
+#    Elevation toward which to converge at map borders
+mapgen_rivers_margin_elev (Margin elevation) float -200.0 -31000.0 31000.0
+
 #    Minimal catchment area for a river to be drawn, in square nodes
 #    Lower value means bigger river density
 mapgen_rivers_min_catchment (Minimal catchment area) float 3600.0 100.0 1000000.0