Index: /trunk/data/validator/deprecated.mapcss
===================================================================
--- /trunk/data/validator/deprecated.mapcss	(revision 14813)
+++ /trunk/data/validator/deprecated.mapcss	(revision 14814)
@@ -1378,2 +1378,10 @@
   group: tr("deprecated tagging");
 }
+
+/* #17383 */
+node[natural=waterfall] {
+  throwWarning: tr("{0} is deprecated", "{0.tag}");
+  suggestAlternative: "waterway=waterfall";
+  fixChangeKey: "natural => waterway";
+  group: tr("deprecated tagging");
+}