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In 2021, Hamas leader said "We have 500 km of tunnels in Gaza". The reason I find it dubious is due to speed of digging. Accodring to Wikipedia, a tunnel boring machine can dig in rock in a speed of about 700 m/week, and in soil (which is more relevant to Gaza strip) about 200 m/week. So, to dig 500 km, they would need 50 years work of tunnel boring machines. But at that time, they had only ruled the Gaza strip for 14 years, and it is not clear they had the most advanced digging technology.

QUESTIONS:

  • Is it possible, with technology available in Gaza, to dig 500 km of tunnels in 16 years?
  • Is there other evidence, not based on Hamas sources, that the length of tunnels under Gaza is anywhere near 500 km?
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    You assume that the tunnel is a linear tunnel with two ends. This is not. This is a complex multipath tunnel. So many workers can dig in one of it.
    – C.F.G
    Commented Nov 21, 2023 at 11:16
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    "Is there other evidence, not based on Hamas sources" What do you think an answer will look like? If we exclude Hamas sources, who is going to have empirical evidence of whether this is true?
    – Oddthinking
    Commented Nov 21, 2023 at 12:29
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    @YouDontSay: Any reason to trust the IDF's estimates over Hamas ones? Both seem to have a incentive to play up the number.
    – Oddthinking
    Commented Nov 21, 2023 at 13:31
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    They aren't talking tunnels like you'd use a tunnel boring machine for. They are talking tunnels that can be anything from a crawlway just barely big enough for a person to squeeze through to larger hollows you could use as storage or gathering places. More like the escape tunnels prisoners dig to get out of prison than a tunnel through a mountain.
    – JRE
    Commented Nov 21, 2023 at 18:20
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    There are two very important factors that you seem to ignore. They didn't use specialized tunnel boring machines, they used people. Some with hand tools, some with power tools and some with the help of explosives. More over, they don't have a single tunnel with 500km length, they have many small tunnels. In several disconnected systems. So they are not limited to a single tunnel but can work on all their tunnels in parallel.
    – SIMEL
    Commented Nov 23, 2023 at 2:53

1 Answer 1

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I made some research trying to find all estimates of Hamas' tunnels. This table summarizes it:1

Length Depth Year Citation
65 feet (20 m) 2014 no cite
500 km 2021 Yahya Sinwar1
300 km 2021 "Israeli army"2
300 miles (500 km) 2021 "Israeli military"3
15 - 60 m 2023 "experts"2
200 miles (300 km) 2023 "reports"4
200 feet (60 m) 2023 "Some Israeli military experts"4
300 miles (500 km) 2023 "Hamas claims"5
500 km 2023 "Hamas meanwhile claimed"6
30 m 2023 "are believed to be"6
45 m 2023 "There are claims"7
500 km 70 m 2023 "is thought to be"8
60 miles (100 km) 2023 "the army previously estimated"9
250 miles (400 km) 2023 "the army previously estimated"9
350-450 miles (500-700 km) 2024 "Senior Israeli defense officials"10

In brackets I have converted the estimates to SI units and rounded to one significant digit. Some sources estimate average or maximum depth and others estimate total length. The source column shows to whom the secondary source (the article itself) credits the figure to. For example, the article ‘Very risky’: Israel faces months-long campaign against Hamas Gaza tunnels cites "experts estimating a depth between a range of 15 to 60 metres", but doesn't specify who those experts are. Note that both Israel and Palestine uses the SI units which, potentially, could be of concern. A journalist in a hurry might not notice that the length is in kilometers and not miles. Or a "helpful" source might convert a figure given in kilometers to miles when speaking to an journalist and not perform the conversion correctly.

There is a lack of authoritative sources. The secondary source either uses passive language ("is thought to be"), indicating that the journalist just "googled it", or cites unnamed experts, or cites the leader of Hamas Yahya Sinwar who in 2021 claimed that Hamas possessed 500 km of tunnels.

Of note are the three estimates following Israel's 2023 invasion of Gaza. Logically, the more time the Israeli army spends in Gaza the more accurate its estimates of Hamas' tunnel network should become (assuming that the Israeli army doesn't deliberately lie to media). The first two of these comes from an December 17, 2023 New York Times article:

Two military officials interviewed after the tour say that recently gathered intelligence indicated that Israel has grossly underestimated the size of the underground network. The system, which the army previously estimated was about 60 miles long, is now believed to be closer to 250 miles long, they said.

This is the only source for the "60 miles" estimate. My guess is that the journalist confused the figure with the well-reported figure of the Israeli army destroying 60 miles of tunnels back in 2021. The latest estimate is from a Times of Israel article:

Senior Israeli defense officials now assess that Hamas’s Gaza tunnel network is between 350 and 450 miles long, far longer than previously believed, according to a Tuesday report. The estimate reported by The New York Times is markedly higher than an Israel Defense Forces’ assessment last month that there are some 250 miles of Hamas tunnels under the Gaza Strip, and an astounding figure given the enclave is only some 140 square miles in total size.

Curiously, the cited New York Times article doesn't contain the 350-450 miles estimate, so it is unclear where it comes from. However, it also cites an official Israeli army source that claims that there are 5,700 tunnel shafts, and that Hamas spent more than 6,000 tons of concreete and 1,800 tons of steel to build the network.

A few articles mention tunnels that the Israeli army has found. In December 2023, the Israeli army claimed that it had uncovered "the biggest Hamas tunnel yet". The tunnel was 4 kilometers (2.5 miles) long and 50 meters deep:

enter image description here

It stands to reason that most tunnel segments must be shorter than 4 kilometers. Whether this tunnel was the longest in the network or just one of many long tunnels is of course unknown.

Here are my conclusions of the evidence. Feel free to draw your own:

  • Unless you trust unnamed Israeli military sources or Yahya Sinwar's word, no credible evidence suggests that the total length of all Hamas tunnels approaches the hundreds of kilometers range. For comparison, Paris' metro is 214 km-long and its sewer system is 2,100 km-long.

  • Same goes for the depth. Deep tunnels face many technical difficulties such as groundwater infiltration, ventilation, lighting, and earth pressure. Gaza's soil is made of sediment of clay and sand so tunnels have to be reinforced with concrete to prevent them from collapsing. Deeper tunnels face more pressure and need more reinforcement.

  1. I first wrote this answer in November 2023 and have updated it.
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    The Paris metro is a poor analogy, and feeds in to the OP's confusion about tunnel sizes. Paris also has 2,100 km of sewers, and 89 km of cooling water pipes. These tunnels are probably even more make-shift than those, given the conditions under which they were built.
    – Oddthinking
    Commented Nov 22, 2023 at 1:17
  • In addition to what @Oddthinking said about not tunnels being the same, no one ever claimed that all of the tunnels are 60 meters deep. The claim is that some of them contain rooms or complexes at this depth, which are probably the most important rooms in the tunnel system. And that those tunnels have the needed tools to keep themselves, like oxygen and electricity generators. The Burj Khalifa is more than 800 meters tall, it doesn't mean that every building in Dubai is at that height and the building stands even though it's hard to maintain such a huge building.
    – SIMEL
    Commented Nov 24, 2023 at 2:22
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    The answer specifies that the depth estimate is for maximum or average tunnel depth. Not that all tunnels are necessarily that deep. However, depth is a factor as depth implies engineering challenges that may be hard for Hamas to overcome due to lack of advanced and heavy machinery due to Israel's blockade of the Gaza strip. Commented Nov 24, 2023 at 2:53

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