One of the purposes of the CSV event upload is to allow testing of functions (e.g. virtual channels or alerts). If you are using the functionality for this purpose you should ideally use a test site to upload the data to rather than the actual live site. There is currently no means to delete or undo any data upload, so once the data is uploaded it will remain there.
As there is no means of removing data and bearing in mind that events should be imported in chronological order, it is recommended that if you wish to run the same data set multiple times for testing the then you should increment the time frame of the data in the CSV file each time you run the test. This will ensure that the data set doesn't overlap the previous test data which may cause invalid test results.