Using below command you can delete log streams based on the date. The logStreamName is appended with date. Using this date you can search the log streams which are not required any more. The below example searches all the log streams within a log group for year 2018. In the name prefix for log stream it searches for all streams starting with “2”. Then based on $log_stream_name_not_to_delete value, it deletes all log stream except for the date defined in $log_stream_name_not_to_delete.
You can download the powershell script using this link-