The most detailed account of Noah's Flood is given in the Book of Genesis. Here there seems little doubt that the Flood had to be truly global and not just "global" in the minds of one minor tribe of people:
All the high hills under the whole heaven were covered…the mountains were covered. And all flesh died…All in whose nostrils was the breath of the spirit of life, all that was on the dry land, died. So He destroyed all living things…the waters were on the face of the whole earth (Gen. 7:19-23; 8:9).