In this verse Strong's H2022 is translated mountains.
Gen 7:20 Fifteen cubits upward did the waters prevail; and the mountains were covered.
But in these verses Strong's H2022 is translated 'hill' or 'hills' (exact same Hebrew word also translated mountain or mountains).
Gen 7:19 And the waters prevailed exceedingly upon the earth; and all the high hills, that were under the whole heaven, were covered.
Exo 24:4 And Moses wrote all the words of the LORD, and rose up early in the morning, and builded an altar under the hill, and twelve pillars, according to the twelve tribes of Israel.
Num 14:44 But they presumed to go up unto the hill top: nevertheless the ark of the covenant of the LORD, and Moses, departed not out of the camp.
Num 14:45 Then the Amalekites came down, and the Canaanites which dwelt in that hill, and smote them, and discomfited them, even unto Hormah.
Deu 1:7 Turn you, and take your journey, and go to the mount of the Amorites, and unto all the places nigh thereunto, in the plain, in the hills, and in the vale, and in the south, and by the sea side, to the land of the Canaanites, and unto Lebanon, unto the great river, the river Euphrates.
Deu 1:41 Then ye answered and said unto me, We have sinned against the LORD, we will go up and fight, according to all that the LORD our God commanded us. And when ye had girded on every man his weapons of war, ye were ready to go up into the hill.
Deu 1:43 So I spake unto you; and ye would not hear, but rebelled against the commandment of the LORD, and went presumptuously up into the hill.
Deu 8:7 For the LORD thy God bringeth thee into a good land, a land of brooks of water, of fountains and depths that spring out of valleys and hills;
Jos 9:1 And it came to pass, when all the kings which were on this side Jordan, in the hills, and in the valleys, and in all the coasts of the great sea over against Lebanon, the Hittite, and the Amorite, the Canaanite, the Perizzite, the Hivite, and the Jebusite, heard thereof;
Jos 10:40 So Joshua smote all the country of the hills, and of the south, and of the vale, and of the springs, and all their kings: he left none remaining, but utterly destroyed all that breathed, as the LORD God of Israel commanded.
Jos 11:16 So Joshua took all that land, the hills, and all the south country, and all the land of Goshen, and the valley, and the plain, and the mountain of Israel, and the valley of the same;
Jos 15:9 And the border was drawn from the top of the hill unto the fountain of the water of Nephtoah, and went out to the cities of mount Ephron; and the border was drawn to Baalah, which is Kirjathjearim:
Jos 17:16 And the children of Joseph said, The hill is not enough for us: and all the Canaanites that dwell in the land of the valley have chariots of iron, both they who are of Bethshean and her towns, and they who are of the valley of Jezreel.
Jos 18:13 And the border went over from thence toward Luz, to the side of Luz, which is Bethel, southward; and the border descended to Atarothadar, near the hill that lieth on the south side of the nether Bethhoron.
Jos 18:14 And the border was drawn thence, and compassed the corner of the sea southward, from the hill that lieth before Bethhoron southward; and the goings out thereof were at Kirjathbaal, which is Kirjathjearim, a city of the children of Judah: this was the west quarter.
Jos 21:11 And they gave them the city of Arba the father of Anak, which city is Hebron, in the hill country of Judah, with the suburbs thereof round about it.
Jos 24:30 And they buried him in the border of his inheritance in Timnathserah, which is in mount Ephraim, on the north side of the hill of Gaash.
Jdg 2:9 And they buried him in the border of his inheritance in Timnathheres, in the mount of Ephraim, on the north side of the hill Gaash.
I quit here about one third of the way thru the Old Testament. But I know there are many, many more times where H2022 is translated hill or hills.
The water covered the hills, not the mountains. It was a local flood.