diff --git a/res/generators/default.lua b/res/generators/default.lua
index 564339b0..5163e0f8 100644
--- a/res/generators/default.lua
+++ b/res/generators/default.lua
@@ -7,9 +7,20 @@ function generate_heightmap(x, y, w, h)
     vmap:noise({x+95, y+246}, 0.15, 3, 35.8)
 
     local map = Heightmap(w, h)
-    map:noise({x, y}, 0.02, 6, 0.2)
-    map:noise({x, y}, 0.06, 7, 0.5, umap, vmap)
-    map:mul(0.3)
+    map:noise({x, y}, 0.02, 7, 0.2)
+    map:noise({x, y}, 0.06, 8, 0.5, umap, vmap)
+    map:mul(0.5)
     map:add(0.3)
+    map:pow(2.0)
+
+    local rivermap = Heightmap(w, h)
+    rivermap:noise({x+21, y+12}, 0.03, 4)
+    rivermap:abs()
+    rivermap:mul(2.0)
+    rivermap:pow(0.18)
+    map:add(0.4)
+    map:mul(rivermap)
+    map:add(-0.2)
+
     return map
 end
diff --git a/src/logic/scripting/lua/lua_type_heightmap.cpp b/src/logic/scripting/lua/lua_type_heightmap.cpp
index 506177ea..b2555103 100644
--- a/src/logic/scripting/lua/lua_type_heightmap.cpp
+++ b/src/logic/scripting/lua/lua_type_heightmap.cpp
@@ -113,7 +113,7 @@ static int l_binop_func(lua::State* L) {
                 }
             }
         } else {
-            auto map = touserdata<Heightmap>(L, 2);
+            auto map = touserdata<LuaHeightmap>(L, 2);
             for (uint y = 0; y < h; y++) {
                 for (uint x = 0; x < w; x++) {
                     uint i = y * w + x;
@@ -132,7 +132,6 @@ static int l_unaryop_func(lua::State* L) {
         uint w = heightmap->getWidth();
         uint h = heightmap->getHeight();
         auto heights = heightmap->getValues();
-        float power = tonumber(L, 2);
         for (uint y = 0; y < h; y++) {
             for (uint x = 0; x < w; x++) {
                 uint i = y * w + x;