All over the planet Earth in every place it starts to rain. A steady rain and it rains for 40 days and 40 nights. That’s 40 twenty-four hour days.
Now it’s my understanding that water is pretty much been the same throughout the Earth’s history. So to get that much rain it’d have to come up from the ocean or from trapped wells in order to come back down right?
What would be the result?
Obviously flooding in low lying areas like Bangladesh? But what about dry places like the Sahara?
Well also say for the purposes of this “What if” the rain is a moderate rain. Wikipedia uses this definition:
So we’ll use the 2.5 mm per hour as the amount of rain per hour.
I can’t even venture a speculation. But how would the world be affected?
Mark, rainfall amounts that are considered “moderate” in one area can be considered “extreme” in another.
For example, the 100-year 24-hour rainfall for my county is about 9.5 inches. A storm occuring with the same frequency on the coast would more likely drop 12 inches of rain. So, you’ve got a little problem with your definition there.
As to the effects, the amount of rainfall doesn’t equal the amount of runoff; you lose some to evaporation, take-up by plants, and soaking into the soil. The amount of losses isn’t equal everywhere (different plants, soil types, temperature & moisture).
The slope of the land also affects the peak flow and the shape of the runoff hydrograph.
Every place on Earth gets 2.4 meters of rain. Being as it’s spread out of forty days, most of it would be flowing from high ground to lower. So let’s just estimate the global sea level would rise somewhere between three and four meters.
You can check out the effects here. Bad news if you’re living in some place like Amsterdam, Venice, Dhaka, or Jersey City. But not the end of the world.
That’s right. Rain water doesn’t come from nowhere. It would have to come from the oceans, or from some previously unknown source.
Of course, you could add some liquid water to the oceans by melting the polar ice caps.
Not only is it going to vary from place to place, it will vary depending on what the weather conditions were like in a place before this rain started. For example, one scenario for a destructive hurricane is to have a hurricane pass over an area that was recently hit by another hurricane. The ground was saturated by the first hurricane, which means more flooding from the second.
In addition to flooding, you could also get mudslides in hilly areas, the way some areas of California do in the winter when they get too much rain.
I assumed, for the sake of argument, that this was some kind of Velikovskian rain that came from somewhere other than the existing terrestrial water supply.
Forty days of rain at a rate of 0.098 inches per hour adds up to about 94 inches of rain. This amount of rain equates to 2.35 inches of rain a day, which is pretty close to a so-called “1-year storm” here in Connecticut. (This is a storm that you’d expect to get once a year, on average.) And you’d be getting this storm every day for 40 days.
All in all, this is a lot of rain–we typically get about 44 inches of rain a year here in Connecticut–but I don’t think that it is of biblical proportions. Our stormwater systems here are designed for a 10-year storm event, which is more than twice as much rain per day.
However, the real issue would be rivers and streams. There would be a lot of localized flooding near these. I wouldn’t want to live near a river or a stream. People in upland areas would probably be fine, but they’d certainly get water in their basements.
The 100-year annual average rainfall here is 10.5 inches = 0.26m.
So getting 2.4m in 40 days would create a significant hydrologolical log jam.
As we are roughly 90m above sea level and it’s almost 1000km to the ocean I’d suggest that water to considerable depth would be backed up, inundating most of south eastern Australia.
At least people would be able to sea that the Murray actually does have an ocean mouth into the Southern Ocean.
The Murray-Darling River system, that drains 2/3rds of south eastern Australia flows into the esturine Lake Alexandrina and then to the ocean via a shallow, narrow between two sand bars. For a lot of Australia’s early (white) history it was thought the rivers flowed to an inland sea. Currently the Murray Mouth needs continual dredging to be kept open.
Our stormwater systems here are designed for a 10-year storm event, which is more than twice as much rain per day.