Binjiang Police Affairs-Chapter 994 - 655: We Might Not Be Able to Go Back! (Part 3)

Despite having been in Jingzhou for many days and having tackled numerous crises, it feels akin to being "firefighters," constantly rushing around without knowing the specifics of both sides of the Jingjiang River, sometimes even struggling to figure out directions.

Now that Master Xi, who understands the situation here best, is here, Han Yu couldn't miss this opportunity. He invited Master Xi to talk to the leaders above the squad leader level right after dinner. 𝑓𝓇𝘦ℯ𝘸𝘦𝑏𝓃𝑜𝘷ℯ𝑙.𝑐𝑜𝓂

As a senior expert at the Linghai Reserve Camp, Master Xi couldn't just enjoy the perks of being an expert without doing any work. He agreed immediately and spoke very earnestly.

"The Ten Thousand Miles of the Yangtze River have their dangers at Jingjiang. This has been a consensus formed over many years during the flood prevention efforts of the Yangtze River. But why is Jingjiang dangerous, and what exactly is dangerous about it?"

Master Xi put down the chalk and pointed at the water area map just hand-drawn on the blackboard: "First, it starts with Jingjiang's geographical location. The Jingjiang section starts from Zhicheng and extends to Chenglingji, covering about 347 kilometers, divided by Ouchi Mouth into Upper Jingjiang and Lower Jingjiang.

The terrain on both sides of Jingjiang is higher in the south than in the north. The South Bank has a terrain several meters higher than the North Bank due to many years of flood diversion and sediment deposition. Historically, most of the North Bank was a low-lying, flood-prone plain formed by the breakup of Yunmeng Lake, intersected by river networks and dotted with lakes, where flood levels during the wet season are significantly higher than the terrain inside the embankments.

Once a breach occurs, the flat Jianghan Plain in Jingbei will be flooded, and it may even directly threaten Hanwu. To resist the ravaging floods, since the year 345 AD, over 1600 years of dynasties have persistently built the Jingjiang Embankment, now stretching about 182 kilometers from Jingzhou Zao Lin Gang to South Jianli City, in the most perilous sites on the North Bank.

The Jingjiang Embankment has constructed an important flood safety barrier for the Jianghan Plain, directly protecting the safety of 11 million acres of arable land, over 10 million people's lives and properties, and the socio-economic development in the area north of Jingjiang, south of Han River, within Jingzhou City, Lingjiang County, Jianli County, Honghu City, Jiangqian City, Taoxian City, part of the plains and lake areas of Han Chuan, and the Jiangbei region of Hanwu City!"

Previously, I always thought that the central and local governments were somewhat biased in water conservancy projects, as the Jiangbei Dam was better built and the embankment standards here in Angong were far inferior to those in Jiangbei. Now I understand the importance of the Jingjiang Embankment in Jiangbei.

Everyone realized the importance and began taking notes.

"Secondly, the Jingjiang River channel's flood discharge capacity is limited. Currently, the Jingjiang Embankment only has a flood control capacity for once in ten years, even if the Jingjiang flood diversion project is employed, it only provides approximately once in twenty years flood control capability."

Master Xi took a deep breath and pointed again at the blackboard: "The maximum safe flood discharge of the Jingjiang section, which includes the flood discharge after the diversion through Jingnan Four Mouths, is about 60,000 cubic meters per second. Based on flood investigations over the past 860 years, the upstream Changyi flood peak flow exceeding 80,000 cubic meters per second has occurred 8 times.

Among them, a flood peak flow exceeding 90,000 cubic meters per second has occurred 5 times, particularly in the massive floods of 1860 and 1870, where flood peak flows reached as high as 100,000 cubic meters per second and 105,000 cubic meters per second, respectively. The 1870 flood in the Upper Yangtze met the Qingjiang flood, marking the Zhicheng flood peak flow at an astonishing 110,000 cubic meters per second, highlighting the huge difference between upstream's floodwater volume and the Jingjiang River's safe flood discharge capacity."

Sun Youyi, formerly an engineering expert, has now become somewhat of a flood prevention expert himself. He raised his hand to ask, "Master Xi, what are the Jingnan Four Mouths?"

"That's a great question. It's what I'm about to talk about regarding the complex relationships between the river and lakes in the Jingjiang section."

Master Xi pointed at the water area map on the blackboard, speaking solemnly: "The upstream water flows from the Three Gorges through Changyi and Zhicheng into the relatively flat terrain of the Jingjiang section, where the riverbed's slope is gentle and the river channel is meandering. The North Bank receives inflow from the Juzhang River, whose outlet is located about 20 kilometers upstream of the Shashi Hydrological Station.

Juzhang River floods mostly occur in July or August, coinciding with the main flood season of the Yangtze River, often meeting with Yangtze floods, which can raise the Shashi water level by 0.1 meters to 0.2 meters.

The South Bank has Songzi Mouth, Taiping Port, Ouchi Mouth, and Diao Xiankou, with Diao Xiankou being controlled by a dam since 1959, leaving only three mouths for natural diversion.

Upstream water diverges through these four mouths into Dongting Lake, blending with inflows around the lake area from the Xiang, Zi, Yuan, and Li rivers and other small and medium rivers. After regulation at Dongting Lake, it flows back into the Yangtze River from Chenglingji, reducing the flood discharge amount through the Jingjiang section and easing the flood pressure on the Jingjiang embankment."

"However, on the other hand, large amounts of sediment carried by the floodwaters flowing into the lake area make Dongting Lake silt and shrink, and coupled with human activities to reclaim land from the lake, Dongting Lake's volume has reduced by more than 100 billion cubic meters over the past century. Moreover, the flood channels at the Four Mouths have gradually silted up, causing the annual diversion of floodwater into the lake to reduce, and the lake's ability to regulate Jingjiang floodwaters to weaken over time."

"Especially when floods from small and medium rivers in the Dongting Lake area meet Jingjiang floods, it creates congestion and elevation at the Chenglingji outlet, Jingjiang floodwaters suffer from compression above and pushing below, making it difficult to discharge efficiently, and the Jingjiang Embankment remains soaked at high water levels for long periods, escalating the risk of emergencies. Thus, the lake-river relationship significantly impacts flood prevention efforts in Jingjiang..."

Without understanding hydrology, how can one engage in flood prevention or rescue?

Everyone gained a lot, listening intently, when Old Han hurriedly burst in.

Master Xi instinctively asked, "Master Han, what's wrong?"

Old Han raised the mobile phone issued by Old Ge in the afternoon and said solemnly, "A colleague from the Hanwu Meteorological Bureau just called, saying a rain cloud suddenly rose near Hanwu Parrot Island and is rapidly expanding like popcorn!"

"Did you say those two air currents met over Hanwu?"

"I'm not sure yet."

Old Han checked his watch and added, "The meteorological satellite will pass over Hanwu around eight o'clock tomorrow morning. We'll have to wait until nine to receive space observation results."

Your predictions are usually inaccurate, aren't they?

Can you keep it that way?

Han Yu suddenly thought that if his father-in-law's predictions were too accurate, it could be problematic, and he couldn't help but ask, "Dad, will it rain in Hanwu?"

Old Han took several deep breaths and said worriedly, "Hanwu is over 200 kilometers from here; my radar can barely observe it. Based on the recent observation results, the humid air current over Hanwu is swirling and has already climbed sharply for over ten kilometers; the massive water vapor will likely turn into torrential rain."

Han Yu pursued further, "How long will it rain?"

"I don't have enough data to say precisely how long it will rain. But one thing is certain, during the ascent of the air current, the ground will form a low-pressure area, attracting more humid air currents to join, which could make rainfall significantly intense and potentially uncontrollable!"

"What about our area?"

"Currently, no rain clouds over us, and it shouldn't rain in the morning tomorrow. However, climate changes quickly—I can't say for the afternoon."

The Jingjiang water level has receded, but not quickly enough.

Master Xi just explained that the Jingjiang water level is so high due to the upper compression and lower pushing effects hindering the discharge. If torrential rain suddenly pours on Hanwu, and the rain is heavy, it will inevitably raise Jingjiang's water level!

Although my father-in-law's 771 radar is quite an old gadget, its main function is rain detection; otherwise, it wouldn't be called 'Rain Probe Radar.' If he says it will rain in Hanwu, it probably nine times out of ten will.

Han Yu realized the gravity of the situation, turned to the crowd, smiled bitterly, and said, "Folks, we might not be going back anytime soon."