The usp_dba_schema_ver_cntrl stored procedure will send e-mail if these schema changes occurred. The best way to run it is through a scheduled job that will run regularly once every night. Please replace recipients string with the semicolon-separated list of the recipients of the mail.
This stored procedure checks the schema_ver and crdate columns in the system table sysobjects. According to the BOL, the schema_ver value gets incremented every time the schema for a table changes. The crdate column stores the date when a table been created. Checking the crdate value prevents anyone from dropping and recreating a table with the same name but different schema.