The idea of a worldwide flood at the time of Noah is a misconception arising out of inexact translations and a misinterpretation of the Biblical text. As supported by a correct translation and understanding of the Biblical text, history, archaeology, logic, and the best available scientific evidence, the flood of Noah's day was a localized flood in the area of the Tarim Basin, located north of Tibet in modern-day western China.
Genesis account - Correct translation - Hebrew word translated as "earth" should be understood as "land" or "country"
According to modern-day translations, the text in Genesis records that waters were on the face of the whole "earth" (Gen. 7:17), and that all life was to be destroyed from the face of the "earth" (Gen. 7:4). The word translated as "earth" in these passages is the Hebrew word "erets" (Strong's Hebrew word #776, check in Strong's Concordance here).
The Hebrew word "erets" can refer to the entire world or planet earth, but also can be translated to mean "country", "field", "ground", and "land" (check in Hebrew lexicon here). "Erets" is rarely used in the Bible to refer to the entire planet, and most often used to refer to a limited geographical area -- eg, it is translated "land" 1,476 times, "country" 140 times, and "ground" 96 times in the Old Testament.
For example, in Genesis 4:14 the King James translation says that Cain was driven "from the face of the earth" when punished by God. Cain was not banished to another planet, but rather from the land or country where Adam and Eve lived.
Historical Evidence - Ancient civilizations have uninterrupted history going back to and before flood
According to the Bible, the flood in Genesis occurred in approximately 2345 B.C. At this period in history, there were many great civilizations existing on the earth. Based upon written historical records and archaeological evidence, we know that several of these civilizations, including those of Egypt, China, and Sumer (Mesopotamia), have an uninterrupted history going back until and before the time of Noah's flood. Egypt, for instance, has an uninterrupted line of Kings from 2000 B.C. going back to at least 3000 B.C. These civilizations were never wiped out by any worldwide flood.
The problem of gathering and storing the entire planet's animals on the ark
Noah was commanded to take two of each species of animal onto the ark. Assuming Noah had to gather animals from all over the earth, are we really to believe that Noah travelled to South America, Australia, Antarctica, and every continent on earth to find every single species of animal, bird, and insect? Further, the ark was woefully small to accommodate for living space and food storage (for almost a year) for earth's estimated 1 million species of mammals, birds, reptiles, and insects.
Understanding that the flood was localized to the area where Noah and his countrymen lived (a region hypothetically the size of the state of Montana or Germany), then the task of taking all species within that area onto the ark becomes possible, and quite feasible.
The problem of all modern human races originating from Noah's family
According to the misinterpretation of the story, all people of the earth were destroyed except for Noah, his wife, and his three sons and their wives. Therefore, we are lead to believe that all the people on earth today are descended from these eight survivors of the flood. But how could Noah's sons and their wives possibly produce the variety in the human races today -- blacks, whites, asians, etc? This is no problem for those who also mistakenly believe that all the human races could have originated from Adam and Eve. As I discussed in a previous article, this is genetically and biologically impossible, and not supported by the Biblical text. The truth is that Adam and Eve are the ancestors of the white race only. And there were other humans on the earth prior to the creation of Adam and Eve, which is why, for instance, Cain feared other people would kill him after he was banished from the garden of Eden, and how Cain was able to find a wife, have his own descendants, and build a city after being banished from Adam & Eve and their descendants.
Location of the Flood
The Bible records that after Adam and Eve were banished from the garden of Eden, they were driven to the east. This is where the descendants of Adam, including Noah, dwelled at the time of the flood. In order to locate this area, we must first know where the garden of Eden was located. Based on ancient extra-biblical sources -- including Chinese, Indian, and Persian traditions -- and the description of Eden given in the Biblical texts, Eden was a land east of Mesopotamia notable for having four rivers flowing through it. Using this evidence, the location of the garden of Eden is most likely the area of the Pamir Plateau, located northeast of the Hindu-Cush Mountains in modern-day Eastern Turkistan. Just east of the Pamir Plateau is a vast area approximately 650 miles long by 350 miles wide rimmed by high mountains known as the Tarim Basin, located in modern day western China. On a related note, one of the ongoing "mysteries" (to many archaeologists) was the discovery in the 1990s of mummies with blonde hair of Nordic-European stock in the Tarim Basin.
This, along with other misunderstandings of the Biblical texts -- including the myth of an earth that is only 6,000 years old and the erroneous belief in the common ancestry of all the human races -- are areas that give support to the notion that the Biblical texts are historically inaccurate, at odds with science, and unreliable as sources -- having disastrous effect upon the faith of millions of people in 'God' and the Bible.
When translated and interpreted correctly, the Biblical texts are credible, and consistent with history, archaeology, and science.
'NOAH'S FLOOD WAS NOT WORLD WIDE' by Pastor Bertrand L. Comparet
Facts & Fictions Regarding Noah's Flood
'AS IN THE DAYS OF NOAH' by Dr. Wesley A. Swift (see second half of article)
'The Flood of Noah' by Pastor Mark Downey