Did Eliyahu need to go away only in order to hide?
Malbim: No. In addition to hiding for safety, he needed to distance himself. He stopped the conduits of influence from Above. He still clung to Hashem, and Birkas Hashem descends on him; it would also descend on where he dwells.
From whom should Eliyahu hide?
Rashi: He should hide from Achav and Izevel (who will want to kill him).
Radak: No one should know where you are. Refer to 17:4:2:2.
Where is Nachal Kris?
Malbim: It is by Eretz Yisrael's border. Normally, when Hashgachah departs, Yisrael can still receive good via nature and Hashgachah. Now, based on nature they should have received rain, just Hashem had to withhold it to fulfill Eliyahu's decree. He will be at the east border to stop rain clouds from coming from Chutz la'Aretz 1 ; influence comes from the east, from where the sun shines.
Hashem can stop the clouds no matter where Eliyahu is! In any case, the eastern border is 400 Parsa'os long, and Eliyahu will dwell in a constricted area! And clouds can come also from other directions! It seems that it was merely most appropriate to be in the east, from which comes the primary influence. (PF)
