This might clear up a few things;
Tip Vortices and Ground Effect yy Dave Pickenpaugh
http://www.torks.com/Guides/THE%20PH...pter%20III.PDF
Note, he is discussing the two types of ground effect as "one".
About lateral airflow, here is an example;
http://www.aerodyn.org/Wings/larw-comp.html The middle image (wing bottom) shows lateral flow from root to tip.
M