Owari Yumeki Golden Day.

Now that he had said that, Shichibei felt much more at ease.

The remaining worry was that Kai was so poor, so incredibly poor, that they hadn't seen any cheap or valuable items. There was simply nothing worth bringing back to Owari; they couldn't very well carry a buckwheat pillow back to Owari.

The famous Koshu silk and Koshu brocade from the Edo period are nowhere to be seen now. Not a single person in Kai is growing mulberry trees or raising silkworms; it's unclear whether they lack the technology, capital, or manpower.

Of course, it may also be related to the fact that the local area is relatively poor and lacks purchasing power.

A hundred years from now, the development of Koshu silk will be largely due to its direct connection to Edo via Hachioji. Edo, as the nation's largest consumer market, can absorb any amount of Koshu silk, no matter how much. Currently, Edo is merely a military town in southern Musashi, not yet boasting a population of one million, and therefore lacks purchasing power.

Sigh, so many days in Kai, what a waste of time.

"The Fuji River can connect to the sea. Haven't you thought about opening it up completely?" After today's class, Nobutsugu Yonekura made a promise about the horse, and Shichibei started to gossip.

"The Fuji River is one of the three major rapids in Japan, making it impossible to navigate by boat." Yonekura Nobutsugu was very interested in having something to teach Shichibei.

The other two rivers are the Kuma River and the Mogami River, which will eventually become the names of cruisers. Of course, there aren't so many explanations now; it's simply that the large elevation difference makes shipping difficult.

However, Shichibei remembers that the Fuji River was used for shipping during the Edo period, but shipping declined when railways were built during the Meiji era. After World War II, when highways were built, shipping on the Fuji River completely fell into disuse, but some sections of the river were retained for sightseeing.

Since most tourists flock to the section around Mount Fuji and Lake Kawaguchi, even the cruise ship industry on the Fuji River eventually went out of business. Shichibei had no recollection of what exactly happened.

"Then why don't you build a weir?" Shichibei was just rambling on.

"What weir?" Nobutsugu Yonekura instinctively pulled out his notebook.

"I haven't traveled the entire length of the Fuji River, so don't take it seriously. Diverting water with weirs is an ancient practice. By blocking water and creating dams, and opening outlets on the dams, the water flows smoothly and without danger."

Indeed, Shichibei had not observed the Fuji River, but the best way to utilize such a high-drop river is through cascaded water use.

The Mississippi River in the United States is a prime example of cascade development. Originally, the Mississippi River had very poor navigability, but through cascade development, it has become a major inland waterway in the United States.

Moreover, the Mississippi River and the Fuji River in the United States have similarities, because the Mississippi River's high-water season coincides with the Caribbean hurricane season. Once a hurricane hits, the Mississippi River's runoff will surge.

The Fuji River is no exception. Once it enters the summer rainy season and a typhoon hits, the flow of the Fuji River will increase several times over, and the water surface will even expand three to five times.

The short, fleeting rainfall periods place extremely high demands on the design of cascade dams across the entire watershed. Furthermore, precise calculations of the flow rates during both the high and low water seasons are required, along with multi-year data.

No wonder the opening of the Fuji River shipping route didn't happen until the Edo period, when resources could be concentrated on major projects. With the Takeda clan's current strength, it's probably still difficult to achieve.

Even if Takeda Shingen conquered Suruga Province and controlled both the upper and lower reaches of the Fuji River, he wouldn't have the resources.

"Shall we go take a look tomorrow?" After writing down the details, Nobutsugu Yonekura stuffed them into his lining and immediately extended the invitation.

Since Niwa Nagahide hasn't reached an agreement with Takeda Shingen yet, Shichibei won't leave easily. The Fuji River isn't far from Tsutsuzaki-no-kan; it takes less than an hour to get there on horseback.

"Huh?" Shichibei was actually not too happy. He was about to get the horse, so why run away?

"Thank you so much!" Yonekura Nobutsugu put on an expression of extreme joy and fear, mounted his horse, and rode off.

Hey kid, don't give me the chance, or I'll make you drink my foot bath water.

………………

Inside the castle, Takeda Shingen found it unbelievable. This Kawamura Shichibei could control floods? Impossible! This man was a horse-riding master, practically a merchant, so it was only natural that he was very astute about various commodities.

Neither Takeda Shingen nor Takeda Nobukazu felt jealous of this. They would be consumed by jealousy. Would Shingen be jealous of Kamiizumi Nobutsuna's unparalleled swordsmanship and spear skills?

Everyone has their own strengths.

But this Shichibei is also quite adept at politics. How could he immediately answer the question about the Fuji River development plan without ever having even seen it once?

The key point is that, based on Takeda Shingen's own experience in flood control, Shichibei's method seemed feasible, or at least appeared so. Takeda Nobukatsu couldn't really argue against it, since his flood control skills were inferior to his brother's.

If the Fuji River could truly be navigable to the sea, Kai would immediately prosper. Large commodities such as timber, stone, and charcoal from Kai could be immediately shipped out in exchange for food and money.

Why is Shinano's timber more famous than Kai's? It's not because Shinano's timber is better, but because it can be sold along the Kiso River to Mino, Owari, and Ise. It can also be transported to Tōtōmi Province via the Tenryū River, and then transshipped to Suruga and Kanto.

This is the advantage of water transport!

Places with waterways can quickly become prosperous and wealthy. Shingen knew this all too well. Unfortunately, Kai and Shinano were both mountainous provinces, making it virtually impossible for them to develop by relying on waterways.

"Xiaoyaoxuan, go and hold off that Goroza for me." Takeda Shingen really wanted to see a complete Fujikawa development plan.

This afternoon, Shingen had actually prepared to agree to Niwa Nagahide's proposal. However, the handmade candles and the Fuji River development plan that suddenly appeared before him made it difficult for him to give them up.

"What! A marriage alliance with the Oda clan is a major event!" Takeda Nobukatsu felt that this seemed a bit frivolous.

"I'm counting on you." Without explaining, Takeda Shingen directly assigned the task to Takeda Nobukatsu.

As the chief scribe of the Takeda clan, what could Takeda Nobukazu do but reluctantly agree?

Niwa Nagahide, who felt that Shingen should accept his conditions, suddenly received an invitation from Takeda Nobukazu, who said he would treat Niwa Nagahide to Yumura Onsen, which is not far from Tsutsuzaki-kan.

The sudden turn of events startled Niwa Nagahide. It was clear that Shingen didn't want to talk to him tomorrow. Had things changed again? No, Niwa Nagahide had already promised to provide Nobunaga's adopted daughter, Toyama-hime, with a dowry of 5,000 kan.

Five thousand kan? Five thousand kan to buy temporary peace, what's so hard about agreeing? You should know that when Nagao Tamekage first started out, his annual income was less than six thousand kan.

Nobunaga spent 5,000 kan to buy peace, so why is Shingen hesitating?

Renko didn't allow Niwa Nagahide to refuse at all. The next morning, he personally came to her door and kidnapped her.

29. Shingen gave me fifty horses.

I'm so envious. Niwa Nagahide and the Takeda family must have had a good talk. Otherwise, why would Takeda Nobukatsu, the head of the Takeda family's clerks, have gotten up so early to pick him up for a hot spring trip?

And look at ourselves, sigh, a bunch of short, muscular Kai men came to our door and dragged Shichibei to see the Fuji River.

Niwa Nagahide was enjoying the lovely and charming hot spring girls, while we saw a bunch of bald men as black as coal.

Depend on!

The group of Takeda samurai were quite pleased, completely unaware of Shichibei's murmurs. Besides having classes again today, a new class representative had arrived. Hmm, the class representative's name was Iifu Genshiro.

Shingen, who was originally a close attendant of the inner palace, is now a general commanding 150 cavalry. If necessary, he can also be reinforced by troops from other provinces and local samurai, and it is not impossible to form a large reserve force of 1,000 men in a short period of time.

"Oh, Genshiro, is it? I've heard so much about you." Shichibei bowed to Genshiro Iifu. Why was he so happy? It wasn't because of this person or anything, but mainly because Shichibei had miraculously met an adult shorter than himself. Genshiro Iifu, who was over thirty years old this year, was at most 1.4 meters tall, not even a little over.

Shichibei, who had been grumbling about Niwa Nagahide sleeping with a hot spring dancer, suddenly became happy again, almost singing, "I'm so happy today, so happy!"

Finally able to ride alongside others, Shichibei asked Iifu Genshiro why he had gotten involved in such trivial matters. Iifu Genshiro's explanation sounded like an excuse; he said that Yonekura Nobutsugu had told him yesterday that he wanted to find fifty horses to sell to Shichibei.

Their family is a prominent family in Kyoma County, owning a horse farm and raising quite a few horses. So they came today to check on Shichibei's needs. Do they want a male? A female? A pregnant one? Or a foal?

Hey buddy, why don't you just have Yonekura Nobutsugu say "I'm passing on a message to the Imperial Army"? Why do you have to come here in person? Only a straightforward samurai like you from Kai would come up with such an obvious excuse.

Whether it's fictional or not, Shichibei doesn't care; what matters most is that he's happy to eat Tomioka Shiro, who's 1.4 meters tall.

I've decided to be your brother, and we must stay in touch!

Let's go, let's head out towards the Fuji River. The hydrological conditions along the Fuji River in the Kaifuchu Basin, or rather, the small plain, are excellent. Since it's a basin, the water is naturally quite gentle.

The elevation difference is mainly concentrated in the mountainous area between Kai and Suruga coastal plains. In fact, the Fuji River is the main connecting route between Kai and Suruga. When Takeda Shingen planned to attack Suruga, his army would primarily traverse this area.

To attack Sunpu Castle, also known as Fuchu Castle in Suruga, by traveling from Mount Fuji to the sea, one would need to conquer castles such as Kamahara, Yui, Okitsu, and Anbara along the way. If it weren't for the successive defections of Imagawa's retainers, it would have been quite difficult for Shingen to penetrate Fuchu Castle, located beside the Abe River.

As for your question about why Shingen insisted on attacking these castles instead of heading straight for Sunpu, it's because, as mentioned before, it's the Suruga coastal plain. You can't force Shingen to fly over mountains and magically land in Sunpu. Controlling these castles along the Tokaido route is crucial; without capturing them, you can't launch a large-scale attack on Sunpu.

Of course, if you only have eight or ten people carrying enough battlefield rations to last a month, then none of the above applies, and flying is also an option.

By the way, the upper reaches of the Fuji River are called the Kamamori River, which refers to a river. The Fuefuki River also flows into the Fuji River, just like the upper reaches of the Qiantang River are called the Xin'an River, and the upper reaches of the Yangtze River are called the Jinsha River, which means the same thing.

Takeda Shingen had already begun to manage the Kamanashi River, but he hadn't completely succeeded. Water conservancy projects, well, throughout the world, are rarely seen as a single, decisive victory. They usually involve annual maintenance, repairs, and gradual improvement.

Besides simply building more dikes, Shingen astutely realized that merely blocking the river was useless. So he constructed the Goose-shaped Dike. You don't need to remember the name; just remember that this dike was a facility that allowed overflowing river water to spill over and enter the diversion zone once a certain level was reached.

Sacrificing the interests of a local flood discharge area to ensure the safety of the entire basin. This tactic was used again in 2024, and videos of the devastating floods in these areas were frequently released. In fact, these areas have been explicitly stated to be unsuitable for habitation and will be subject to flooding if necessary.

There's no way around it; people are attached to their homeland and many are reluctant to leave such a large flood discharge area empty.

Then, a low dam is built around the perimeter of the diversion or flood discharge area to block the spreading floodwaters and control the extent of the flood's impact. In any case, floods in Japan last at most three to five days, and the water recedes as soon as the typhoon subsides, which is enough to save most of the paddy fields.

To ensure the annual maintenance of the dike, Shingen established the Kawamata-shu, or Kawagawa-ku-shu, exempting them from taxes and ordering them to reside in villages along the riverbank. Their duties included repairing the dike in peacetime and standing guard against floods during times of disaster.

After twenty years of continuous efforts in water management, the flooding problems of the Kamanashi River and Fuefuki River have been greatly reduced. As long as we continue to strengthen the construction of water conservancy facilities, divert water and build weirs, dredge river channels, and dig more ditches, the floods of the Kamanashi River will eventually be tamed by humankind.

The river channel more than 30 kilometers downstream from Tsutsuzaki-no-kan is completely unnecessary to build a weir. The channel is relatively calm, and the flow is adequate. Navigation is difficult for large navigable boats, but perfectly fine for smaller ones.

All the way up to Fanfu Village, or Fanfu region, is river valley terrain with many paddy fields and terraced fields on hills, and the terrain is generally flat. But further south, towards Xiashan City, the elevation difference gradually increases, the river valley narrows, and paddy fields become scarce.

Mountains with an elevation of over 1,000 meters are everywhere, such as Mount Shichimen, which is 2,000 meters high, and Mount Takatori and Mount Ochika, which are both over 1,000 meters high. The Fuji River will then rapidly change from an average elevation of a few hundred meters to an elevation of three to five meters in the next few dozen kilometers of its course.

It would be strange if the water wasn't rushing.

The group continued down the mountain after passing Shimoyama Castle, all the way to Gotenyama. Shichibei immediately pointed to the narrowing river channel and said that a weir and a waterway should be built here.

The Shankai Pass and Yudian Mountain are flanked by a river, and the fact that the river has not eroded the two mountains over thousands of years indicates that the foundation here is stable. After constructing the river weir, setting up water diversion outlets and, if necessary, flood discharge ramps, will ensure the safety of the weir.

What Shichibei didn't know was that Kakukura Ryo, a prominent merchant in the early Edo period, had set up the first shipwreck shelter and flood refuge in the Kai direction at this location.

Iifu Genshiro didn't respond, only nodded, and instructed the Kai samurai behind him to take notes. Shichibei glanced at the sky; it was already noon. "Let's head back."

Having not even reached the border, Iifu Genshiro naturally refused, stating that they could continue further. He had come to help Shingen obtain Shichibei's strategy for managing the entire Fuji River, and naturally, he was unwilling to turn back now.

So Iifu Genshiro said they could rest in Iifu Village that night and there was no need to rush back to the city. In any case, Niwa Nagahide had been invited by Takeda Nobukatsu to go to the hot springs and wouldn't be back for a day or two.

Huh? Niwa Nagahide was taken away early this morning, how did you know?

Shichibei was a little puzzled, but he didn't show it. Since they had invited him, he might as well go along with it; a guest should follow the host's lead.

After having a meal in a small village, the group continued their journey. Looking at the turning Fuji River, Shichibei suddenly realized that his plan to divert the water and build a dam might not be necessary.

Why? Because of Mount Fuji.

Mount Fuji, an active volcano, was formed in the last tens of thousands of years due to intense geological activity and tectonic plate compression. Originally, this area should have been a flat plain or a depression, submerged below sea level.

Volcanic eruptions and tectonic plate collisions have created this massive mountain.

What does the presence of Mount Fuji mean? It means that the Fuji River, which originally flowed straight down from Kai Province, cascading three thousand feet, is now bisected by Mount Fuji. The river channel has changed from a vertical "丨" shape to a "《" shape.

There was no other way; the Fuji River couldn't possibly wash away Mount Fuji. So the only option was to bypass Mount Fuji, resulting in a large bend in the waterway.

No wonder the Fuji River was navigable in history!

I understand now, I completely understand. In later junior high school history textbooks, there's a high slope on the Beijing-Zhangjiakou Railway that trains can't climb. How did Zhan Tianyou design it? He used a "human" shaped railway track, allowing the trains to turn up the slope step by step.

Similarly, Fuji River transformed itself into an overturned "human" shape, thus making it possible to cross the rapids and treacherous shoals that would otherwise be insurmountable.

The Fuji River is 120 kilometers long. Excluding the upstream 30 to 40 kilometers, which are mostly mountain streams and creeks, and not counting the several tens of kilometers of flat riverbed or valley between mountains in the Kai Basin and the coastal plain of Suruga downstream, the truly dangerous section with rapids is the 30 to 40 kilometers of riverbed at the border of Kai and Suruga.

The significant elevation difference originally made it a formidable barrier. However, the river's winding course led to solutions for its management.

During the dry season, an earthen dam is built, and the river channel is dredged to remove boulders, steps, and deep pits. The river channel is then widened by dredging to ensure that small boats can pass.

One dredging operation can last at least thirty to fifty years. If siltation occurs afterward, that's a problem for future generations.

Don't expect to do something and have it last for 10,000 years. To date, I've never heard of a project that can be guaranteed to last for 10,000 years.