The question has been around for a long time. Was the flood local or global. To answer that we must first look at the Bible account and in Genesis 7:11 it says the fountains of the great deep were broken up. All over the world there are canyons that cover the Globe under the water and in some areas there are large deep holes that for no reason are there. One canyon is deeper than Mt Everest itself. So if there is physical evidence of these holes and canyons under the water, is there evidence of water under there that could erupt and come out. In 2014 scientists published the findings of long research into the earths crust and found that 660 Kilometres below the surface of the earth is a substance they call Ringwoodite that exists between the mantle and the molten core of the planet which is blue in colour but also acts like a giant sponge and contains three times the volume of the worlds oceans. Release that and it would cover the world with water but high mountains like Mt Everest would not be covered. But on Mt Everest high up on the sides are sea shells so if there was a severe movements of the plates and it pushed up the mountains like that it would explain these severely steep mountains exist today.
Genesis 8:1-5 talks about the water continually decreasing from off the earth. Where did it go back to ? It went back to where it came from in this Ringwoodite layer of the earth and there it is today.
God made a covenant with Noah that He would not flood the earth like that again to destroy the earth. The sign of the covenant is the rainbow. If the flood was local how come we see the bow over the entire earth ? If the flood was local did God forget his covenant as many people have lost their lives in local floods and in Indonesia over 200,000 people died in a flood so was there never a rainbow there to say that there is a covenant between Him and the people of the earth ?
Matthew 24:37-44 Jesus refers to His return as to be like the flood that came in Noah’s time where some will be taken and some left behind. Are we really believing that the flood was local then we must believe that the return of Jesus is only local and that He won’t be here in Australia to lift us up as His appearing is only taking place locally in Israel. Then the judgement of fire must be local and not world wide so at the return of Jesus He will just be in Jerusalem and life will go on the same here in Australia. In 2 Peter 3:5-12 it mentions that the world that was then overflowed with water and the earth is reserved for judgement by fire “The earth also and the works therein shall be burnt up” The Bible does not contradict itself as some say If we accept that the flood was global then we accept that the return of Jesus is global and His appearing will be worldwide for He sends His angels to gather His elect from one end of the earth to the other. Then just as the judgement of man was with a global flood then in the future the judgement of fire will be a global one too.