What is the meaning of "Tis'haleli"?
Rashi: You boast.
Why does it say "ba'Amakim"?
Rashi: Your land is a land of valleys. Lack of rain is not difficult for it, for the sun does not rule over it (it is mostly shaded).
Radak: [It boasted about] its plains; it had much grain.
Malbim: This is Ir ha'Mayim that was in front of Rabah (Shmuel II, 12:27), a valley full of water. Others could not conquer it due to the water around it.
What is the meaning of "Zav Imkech"?
Rashi citing Menachem: An affliction of excess rain came, and the water flowed in the valley and flooded the roots of the grain.
Radak: The plain that you boast about will flow with blood of your dead bodies.
Radak citing Targum Yonasan: Your strength will be destroyed.
Why does it say "ha'Botchah b'Otzroseha
Malbim: It had great storehouse of grain for a time of siege, and said 'who will come to conquer me?!'