“At the risk of stating the obvious, wouldn't a worldwide Flood eradicate all traces of these four antediluvian rivers? Such a catastrophe would've utterly rearranged the topology of the earth, I think.”
I don’t know that a global flood would eradicate all trace of preexisting rivers. Your statement contains a number of unspoken assumptions which we’d have to explore.
As you know, rivers are, themselves, a major source of flooding. In river valleys, the rivers often overflow their banks during the snowmelt, or due to heavy rain upstream, and flood the surrounding land. They then revert. Parts of Bible history are, themselves, situated on floodplains like Mesopotamia and the Nile River valley. Riverine flooding doesn’t obliterate the rivers which are the medium of such flooding.
i) Presumably you think a global flood, due to its great scale, would obliterate preexisting rivers. Are you attributing that to diluvial erosion?
If so, I think that would depend, in part, on the flood mechanism or drainage mechanism we postulate, as well as the rate of inundation or drainage.
As you know, the Bible cites two flood mechanisms: rain and the “fountains of the deep.” The latter expression is considered to be “poetic,” so we have to speculate on what is literally in view.
Does torrential rain obliterate rivers? Not in my experience. Also, once the land is submerged to a certain depth, isn’t there a difference between the water action at or near the surface and the water action near the riverbed?
What about the “fountains of the deep.” Doesn’t that suggest coastal flooding? Wouldn’t that involve a more gentle and gradual action? Does rising water have the same erosive power as running water?
I’d add that some rivers are tidal rivers. Because they feed into the sea, the sea level affects the river level. High tide raises the river level as seawater backs up into the river channel.
Drainage can obviously be erosive, but that also depends on the rate of runoff. And, of course, rivers are both natural flood mechanisms as well as natural drainage mechanisms.
Gen 1:9 suggest orogeny. The dry land was formed by rising out of the sea. Hills and mountains form natural barriers to flooding. God could flood the earth by reversing the process. Lowering the mountain passes. Or breaching them—like a breach in a dike or a dam.
How much water is needed to inundate the earth would, of course, depend on how high above sea level the high ground lies. There are two ways of flooding the earth. Raising the sea level or lowering the high ground.
It doesn’t take much water to inundate a river valley or flood plain since the dry land is low-lying. The Bible doesn’t give us much information, so many scenarios are possible.
ii) Or were you suggesting that the pressure of the water at extreme depths would obliterate the preexisting riverbanks?
If so, this assumes that the floodwaters were extremely deep. As I’ve just suggested, that isn’t the only alternative—even for a global flood.
Also, we’ve all seen pictures of (or read about) seabeds where, despite the immense pressures, the ocean floor isn’t flattened out like a steamroller. Indeed, some rather delicate looking creatures survive down there.
Likewise, does standing water have the same erosive power as running water?
I’m not a hydrologist or geologist, so I can’t give you expert answers. I’m just suggesting some of the variables that you’d need to factor into your answer.
“I understand that there is some disagreement among scholars regarding whether the Noahic flood was global or local, but it seems ridiculous to have Noah spend 120 years building an ark to avoid a flood he could simply walk away from.”
i) Scholars disagree on whether the 120-year figure has reference to the interval between the divine warning and its execution or else a general lowering of the human lifespan.
ii) It’s also easy for us to forget that the ark, while functional, is not a practical necessity.
a) For one thing, if God can miraculously spare Daniel’s friends from incinerating heat, or sustain Jonah in the belly of the “whale,” then he doesn’t need an ark to preserve Noah and his family—or a variety of fauna.
In fact, God often does things which are not strictly necessary to make a point. Consider the rigmarole of the ten plagues and the parting of the Red Sea. God could have liberated the Israelites by a far more efficient means.
But he was using very dramatic methods to score symbolic points. To humiliate the cult of Pharaoh. To ridicule Egyptian mythology.
Yes, in the case of local flood, Noah would be able escape if God simply told him that on such-and-such a date, he was going to inundate the area. But that wouldn’t illustrate the principle of divine deliverance.
b) In addition, the purpose of the ark is more than merely utilitarian. It’s a symbolic craft. A floating temple. A microcosm of the cosmic temple. As one scholar explains:
“What is now to be observed is that the design of the ark suggests that it to was intended to be a symbolic representation of God’s kingdom in this cosmic house form. For the ark, however, seaworthy, was fashioned like a house rather than like a sailing vessel. All the features mentioned in the description of the ark belong to the architecture of a house: the three stories, the door, the window. More specifically, these architectural features of the ark match up with features in creation’s cosmic house as that it figuratively envisaged in various biblical passages, including the flood narrative itself.”
“The three stories of the ark correspond to the three stories of the world conceptualized as divided into the heaven above, the earth beneath, and the sphere under the earth, associated especially with the waters (cf. e.g., Exod 20:4; Deut 4:16ff.; Rom 1:23). Possibly the idea of three such zones is reinforced by the animal lists which classify the creatures in the ark as birds of the heaven, cattle and beasts of the earth, and the creeping things of the ground (Gen 6:7,20; 7:23; 8:17; cf. 7:14,21; 8:19). The third category, the creeping things, might have special reference here to burrowing creatures whose subterranean world would then have been substituted for the sphere of the waters under the earth as the lowest level of the ark-cosmos. Or does the narrative intend the correspondence of the first story of the ark to the waters under the earth to be suggested simply by the fact that this lowest part of the ark was actually submerged under the waters of the flood?”
"Clearly, the window of the ark is the counterpart to ‘the window of heaven,’ referred to in this very narrative (7:11; 8:2). Appropriately, the window area is located along the top of the ark, as part of the upper (heavenly) story. One is naturally led then to compare the door of the ark with the door that shuts up the depths of the sea, holding back its proud waves. (For this cosmological imagery see Job 38:8-11.) Precisely such a restraining of the mighty surge of waters was the function of the door of the ark, once the Lord had secured it about the occupants of the ark at the outset of the deluge. Together, the window and door of the ark mirrored the two cosmic sources of the floodwaters, the window of heaven, opened to unleash the torrents of the waters above the earth, and the door of the deep, unbarred to let the waters beneath the earth break loose.”
“Another indication of the cosmic house symbolism of the ark is that it is God himself who reveals its design. Elsewhere when God provides an architectural plan it is for his sanctuary-house, whether the tabernacle or temple (Exod 25:ff. 1 Chron 28:19; Heb 9:5; cf. Ezk 40ff.; Rev 21:10ff.). As the architect of the original creation, who alone comprehends its structure in all its vast dimensions (cf. Job 38), God alone can disclose the pattern for these microcosmic models,” M. Kline, Kingdom Prologue, 225-27.
So even if the flood was a local flood, you could still have an ark like Noah’s ark—for emblematic reasons.
“With regard to tracing the ancient names, isn't it reasonable to assume that Noah's descendants may have named features of the post-Flood landscape after those destroyed by the Flood?”
i) Yes, it’s possible to name new places by reusing old place names. When Englishmen colonized parts of North America, they named some of the towns they founded after some of the towns they left behind. But that’s a case of using the same names for different landmarks. I don’t see how that fits the context of Gen 2:10-14.
The primeval rivers are part of the antediluvian landscape. That’s the address of Eden.
Yet the narrator is writing long after the flood. He’s using names for landmarks which his audience would recognize. Telling them where Eden was located.
Doesn’t that imply continuity between the status quo ante and the status quo quem? It’s not using old names for a new location. It’s naming an old location, citing the original landmarks as coordinates.
ii) Moreover, Mesopotamia is a natural flood plain. So a reader who’s acquainted with Mesopotamia might well associate the flood with local conditions. The Tigris and Euphrates (among others) are indigenous flood mechanisms.
iii) Furthermore, that would also explain why the ark came to rest in the same region (Gen 8:4). The waters receded in the same general area where they originally arose—since the same rivers also serve as natural drainage mechanisms.