It's hard to reply when you use straw men arguments like "40 days". I'm not saying you are willfully doing so, by the way. You may be unaware that the Bible teaches that:
1) The planet was shaken catastrophically during the Flood.
Genesis 7 NIV
That's the whole of Genesis 7.
You can call it a straw man if you wish, but your source material clearly makes the claim that the "waters of the deep", along with heavy rainfall, released themselves over a 40 day period. The whole world was supposedly drowned for less than 6 months (150 days), and then everything went back to normal... So within a time frame of 5 months, all of this catastrophic upheaval took place
If, as you say, the mountains were washed away and/or seriously eroded, is this something that happened within those 150 days?
Are you also going to make the qualifying remark on the height of the waters being 23 feet above even above the highest mountains, or are you going to take the more rational stance that the entire flood was only 23 feet high, the latter of which poses very obvious problems for the claim that this flood killed everything...
And if, as you say, there is a complementary claim made by "Creation Scientists" which states that other catastrophes and highly volatile volcanic events happened in conjunction with this global deluge, then I'll happily address those as well. All those creationists have to do is support their claim with some physical evidence. All they need to do is show incredibly similar radiometric dates for geologic strata that are otherwise non contiguous...
For the record, I haven't brought up the fact that your source material also claims that the protagonist was 600 years old at the time, just to give you the benefit of the doubt.
2) Only some of the waters came down via rain over 40 days.
Correct. The rest of flood waters supposedly came from under the Earth, right?
Still, however, it was over a 40 day period according to your source material.
Would you contest your source material?
Either way, in your defense of this creationist deluge story, you've already readily admitted that there isn't enough water anywhere in this closed system of a planet to cover the Earth at any depth, let alone the great claim made by the actual story in the Bible...
Out of curiosity, how do the Creation Scientists deal with this apparent statistical conundrum?
If there was a flood, but there wasn't enough water, how was there a flood?
3) Most creation scientists believe there was a post-Flood ice age as just one of many geology-altering events that followed in the wake of the Flood. In fact, there would have been centuries of upheavals, drastic changes, and likely, extreme volcanism.
Oddly enough, we know when the last few ice ages occurred and we know how they altered the landscapes. We know when, where, and how glaciation affected the local geology and we know this because we can observe it's effects. We can hop in a car, right now, and drive to places to study the marks left of the face of the Earth from the most recent Ice Age. We can dig down a little bit, or travel to places where natural erosion has exposed the remnants of Ice Ages prior to that one... Is it safe to assume, based on your arguments, that the Global Biblical Deluge (which couldn't have happened as described because there isn't enough water anyway) happened during one of these known time periods?
110,000 - 12,000 years ago... There's plenty of evidence of animal life before, during, and after that time period. I'll go to back yard this afternoon and dig up some evidence to show you if you don't believe me.
Past Climate Cycles: Ice Age Speculations
This link will be helpful.
Regardless of whether or not you say yes or no to the question of if the Global deluge took place just before these most recent Ice Ages, there are some serious and obvious contradictions to your source material that will have to be addressed...
You know, I have a cousin who revealed last Thanksgiving that he was a YEC. He jumped himself into a conversation that my sister (an Archaeologist) and I were having about some ancient native peoples out in Arizona. The conversation drifted towards my memories from visiting Badlands, NM and the Grand Canyon a few years ago and then obviously into the age of strata and layers and so on. He piped up with his not-on-topic rationalization about how Dinosaurs were just regular lizards that didn't die for hundreds or thousands of years. Lizards don't stop molting, he said, and have no limit to the size they can grow. So dinosaurs are little more than just really aged reptiles. He also argued that there have only ever been 3 triceratops found and that means that there's no evidence that more could have ever existed. He also said that there used to be an extra layer to the atmosphere, made of nothing but water, that God kept there just in case something bad happened and that he popped that layer at the time of the flood, thus adding to the totality of water necessary to completely flood the earth. All of that water then sank deep into the Earth, just below where our sensors can detect water today. He also said that all of the polar ice caps melted in a matter of seconds, which , if you ask me, is more a magical feat than taking 40 days to flood the whole place. The amount of global warming required to cause such a calamity would have baked Noah and his little boat faster than bacon under the broiler... His arguments were similar to yours, the only difference being that he was more true to his source material...
The point I'm trying to make is this:
Faith is not dependent on factual events. As such, for your own credibility, I suggest you stop attempting to jump through so many mental hoops in order to make the argument that these fantastic events were actually historically factual... Don't be like my cousin and make yourself look like a loon at dinner.