Analysis Method for Riverbed Deformation and Estuary Flood and Tidal Standards

Abstract

The present invention discloses a standard analysis method for riverbed deformation and estuary floods, comprising the following steps: first, investigating and collecting estuary topography and flood characteristics to determine the relationship between riverbed deformation and the lowest water level at key sections; second, determining the relationship between riverbed deformation and the maximum tidal flow at the estuary; third, determining the relationship between the change in the maximum tidal flow at the estuary and the change in the highest water level at key sections; and fourth, determining the relationship between the flood recurrence period and the change in the highest water level at key sections. Using the present method, the previous riverbed topographic conditions are inverted by comparing the current and previous changes in the lowest water levels at key sections. The change in the flood recurrence period under current conditions after significant natural riverbed incision is determined. This provides a scientific basis for addressing major water safety issues such as the reduction of estuary flood-carrying capacity and tidal-receiving capacity due to riverbed siltation, as well as for reviewing, evaluating, and ensuring operational safety of excessive floods. This provides technical support for subsequent scientific management, resulting in significant socioeconomic and environmental benefits.

Description

Technical Field

[0001] The present invention relates to the fields of hydraulics and river dynamics, and in particular to a standard analysis method for riverbed deformation and estuary flooding. Background Art

[0002] An estuary generally refers to the section of a river where it flows into the ocean. This estuary is influenced by both oceanic and river hydrodynamics, resulting in the interaction of these two processes. Water conservancy facilities at estuaries generate significant socioeconomic benefits in flood control, increasing available water resources, improving navigation conditions upstream of sluice gates, enhancing urban waterscapes, and promoting urban water culture.

[0003] The Netherlands has often been hit by storm surges throughout history. The flood in 1953 killed more than 1,800 people and left 100,000 homeless. After the construction of the Dutch Delta Project, the flood control standard was raised from once in 1,250 years to once in 4,000 years, protecting one-third of the Netherlands' land area and 4.5 million people. London, England, is located at the mouth of the Thames River and is prone to frequent floods. From 1791 to 1953, the flood level in the basin rose by 1.2 meters. In the 1953 flood, the surge reached 5.41 meters, the east coast was flooded, and more than 300 people died. After the Thames Barrier was built, the flood control level was raised from 5.28 meters to 6.9 meters, which can withstand high water levels that occur once in 1,000 years and protect 125km of London. 2 The Thames Barrier is a landmark of London and a beautiful landscape. The Cardiff Bay Estuary Barrier in the UK has created a 200hm 2 The freshwater lake formed a 13km developable beach, replacing the mudflats formed by the original tidal range, making Cardiff Bay the leading emerging fashion port and economic development engine in Europe at that time, and realizing the dream of Cardiff's urban revitalization. 2 and 50km 2 The upstream river-type reservoir of the sluice gate can add 243 million m3 of water for agricultural irrigation and general industrial use on the plains on both sides of the strait each year. 3 and 250 million m 3 , solved the problem of water shortage in the estuary area; after the construction of the sluice gate at Sheyang River estuary in Jiangsu Province, a reservoir capacity of 30.797 million m 3 The "moon" shaped reservoir directly benefits 466,700 hectares of rice fields. 2 .

[0004] On the other hand, estuary water conservancy facilities also significantly change the natural water dynamics and water and sand transport patterns of the estuary, which will have a huge impact on the project itself and the surrounding environment. The first is the problem of the project's own safety, use function and river siltation. The small and medium-sized rivers in Japan and India have serious siltation below the sluice gates, and some estuaries are completely blocked. Among the 58 tidal gates built along the coast of Jiangsu, my country, 5 are basically silted up, 15 are seriously silted up, and 20 are generally silted up; among the 35 estuaries with sluice gates in the Haihe River Basin, 22 are seriously silted up, and the water-passing capacity of the river channel below the sluice gate has decreased by 60%. After the construction of the Haihe River in Tianjin, the riverbed siltation height was 4.7m, the river width was narrowed from 250m to 100m, the water-passing section was reduced by 85%, and the estuary discharge capacity was reduced from 2100m 3 / s dropped to 800m 3 / s. Meanwhile, the construction of other estuary water conservancy facilities has significantly reduced the amount of sand flowing from upstream. Combined with human activities such as sand mining and channel dredging, the natural riverbed has been significantly incised. For example, the dry season water level below the Shuikou Hydropower Station, 117 km from the Minjiang River estuary, dropped by 4.42 meters in just 16 years from 1991 to 2007. The dry season water level below the Jinji Gate, 19 km from the Jinjiang River estuary, has also continued to decline, dropping a further 1.87 meters from 2004 to 2019. The peak flood levels in 2010 at the Beixi Punan hydrological station, 40 km from the Jiulong River estuary, and the Xixi Zhengdian hydrological station, 48 km from the estuary, were 4.16 meters and 3.25 meters lower, respectively, than in 1960.

[0005] Estuary water conservancy facilities serve as a crucial barrier protecting urban residents and critical infrastructure from tidal floods, shouldering the crucial task of protecting people's lives and property. The impact of severely deformed riverbeds on the flood and tide standards of estuary water conservancy facilities and embankments is not only directly relevant to project investment, the safety of these facilities, and countermeasures against excessive floods, but also to the scientific management of estuary human-water harmony and the urban quality. However, current research indicates that no analytical methods for riverbed deformation and estuary flood and tide standards have been reported, either domestically or internationally. Therefore, the development of technologies for determining riverbed deformation and estuary flood and tide standards is urgently needed to meet the needs of ecological civilization, engineering development, and social progress in my country. Summary of the Invention

[0006] (1) Technical problems to be solved

[0007] Estuarine flood standards are the design criteria for estuary water conservancy facilities, directly impacting the overall layout, structural design, construction cost, and operational safety of estuary water-related structures. Drastic riverbed deformation can significantly impact estuary flood standards. The primary technical problem addressed by this invention is to determine the impact of riverbed deformation on estuary flood standards and clarify the relationship between riverbed deformation and the lowest water level at key sections of the river, the maximum tidal flow at the river mouth, the highest water level at key sections, and the flood recurrence period. This technology, through its use, aims to ensure the needs of ecological civilization, engineering construction, and social progress in my country.

[0008] (2) Technical solution

[0009] The purpose of the present invention can be achieved through the following technical solutions:

[0010] The standard analysis method for riverbed deformation and estuary flooding includes the following steps:

[0011] The following steps are involved:

[0012] Step 1: Investigate and collect data on the topography and flood characteristics of the estuary, and determine the relationship between riverbed deformation and the lowest water level at key sections;

[0013] Step 2: Determine the relationship between riverbed deformation and maximum tidal flow at the mouth;

[0014] Step 3: Determine the relationship between the change in the maximum flood flow at the mouth and the change in the highest water level at the key section;

[0015] Step 4: Determine the relationship between the flood recurrence period and the change in the highest water level at key sections.

[0016] Furthermore, the relationship between the riverbed deformation and the lowest water level of the key section in step 1 is determined by the following formula:

[0017]

[0018] Among them WL dmin (t i ) is the dry season t i The lowest water level of key sections in the year (unit: m), D riverbed (t i ) is the tth i Annual riverbed deformation value (unit: m), siltation is positive and incision is negative.

[0019] Furthermore, the relationship between the riverbed deformation in step 2 and the maximum flood flow at the mouth is determined by the following formula:

[0020]

[0021] where Q rmax (t i ) is the tth iMaximum tidal flow at the mouth section of the year (unit: m 3 / s), with a negative sign indicating that the rising tide is in the opposite direction of the river flow.

[0022] Furthermore, the relationship between the change in the maximum flood flow at the gate and the change in the highest water level at the key section in step 3 is determined by the following formula:

[0023]

[0024] Where △WL cmax is the water level change value of the key section (unit: m), △Q rmax is the change value of the maximum flood flow at the gate in different years, taking the absolute value (unit: m 3 / s), e is the exponent, and the calculation is accurate to 2.7182818.

[0025] Furthermore, the relationship between the flood recurrence period and the highest water level of the key section in step 4 is determined by the following formula:

[0026]

[0027] where n p is the current flood recurrence period (unit: year), WL rmaxb It is the highest water level of the key section in the original recurrence period, unit (m).

[0028] (3) Beneficial effects of the present invention:

[0029] The technical solution of the present invention can very conveniently and accurately determine the impact of riverbed deformation on flood standards, improve the flood standards of water conservancy facilities affected by severe riverbed incision in the estuary area, and provide a scientific basis for scientific countermeasures to major water safety issues such as the reduction of estuary flood-carrying capacity and tidal capacity due to riverbed siltation, as well as the review, evaluation and operational safety of excessive floods. Moreover, the re-identification of tidal flood standards caused by riverbed deformation in this solution is of great significance for the design and layout of dams in tidal areas, urban flood and tide prevention design, waterscape design, waterway construction, planning and site selection of ports and terminals, safety of cross-river subways and bridges, and control of pollutant migration. It can effectively improve the needs of my country's ecological civilization, engineering construction and social progress, and has obvious social, economic and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is the river course plan layout diagram of the present invention.

[0031] In the figure: Section 1 of the Jinjiang River estuary at Qiangcheng, the key section below Jinji Gate, Section 2, the Jinjiang River estuary section entering the sea, Section 3, and the East China Sea, Section 4. DETAILED DESCRIPTION

[0032] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0033] Example 1:

[0034] Step 1: Investigate and collect information on the topography and flood characteristics of the estuary, and determine the relationship between riverbed deformation and the lowest water level in the dry season at key sections. This embodiment uses the Jinjiang River estuary as an example:

[0035] It is known that during the dry season of 2004, the lowest water level below the key section of Jinjiang River, Jinji Gate, was -0.07 m. Using Formula 1, the riverbed deformation value in 2004 was determined as:

[0036]

[0037] It is known that under the dry season conditions in 2019, the lowest water level below the key section Jinji Gate is -1.803m. Formula 1 is used to determine the riverbed deformation value in 2019:

[0038]

[0039] By applying Formula 1 above, it can be shown that the riverbed of the Jinjiang River estuary was cut down by 2.38m in 2019 compared with 2004.

[0040] Step 2: Determine the relationship between riverbed deformation and maximum tidal flow at the mouth:

[0041] The maximum tidal flow at the Jinjiang River estuary in 2004 was determined by applying Formula 2:

[0042] Q rmax(2004) =104.47×D riverbed(2004) 2 +550.34×D riverbed(2004) -3236.2

[0043] =104.47×(0) 2 +550.34×(0)-3236.2=-3236.2(m 3 / s)

[0044] According to formula 2, the maximum tidal flow change at the mouth in 2019 is determined as:

[0045] Q rmax(2019) =104.47×D riverbed(2019) 2 +550.34×D riverbed(2019)-3236.2

[0046] =104.47×(-2.38) 2 +550.34×(-2.38)-3236.2=-3954.25(m 3 / s)

[0047] △Q rmax =Q rmax(2004) -Q rmax(2019) =-3236.2-(-3954.25)=718.05(m 3 / s)

[0048] Step 3: Determine the correlation between the change in the maximum flood flow at the mouth and the change in the highest water level at the key section:

[0049] According to formula 3, the water level change value under Jinji Gate at the key section of Jinjiang River from 2004 to 2019 is determined as follows:

[0050]

[0051] Step 4: Determine the changes in flood tide standards caused by changes in the highest water level at key sections:

[0052] It is known that the original 100-year water level W below Jinji Gate, a key section of Jinjiang River, is rmaxb The flood recurrence period is 11.06m, and the formula 4 is used to calculate the current flood recurrence period:

[0053]

[0054] This indicates that the flood tide standard below Jinjiang Jinji Gate has changed significantly from once in 100 years to once in 200.47 years.

[0055] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in similar ways. As long as they do not deviate from the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A standard analysis method for riverbed deformation and estuary flooding, characterized by: The following steps are involved: Step 1: Investigate and collect data on the estuary topography and flood characteristics, and determine the relationship between riverbed deformation and the lowest water level at key sections; Step 2: Determine the relationship between riverbed deformation and maximum tidal flow at the mouth; Step 3: Determine the relationship between the change in the maximum flood flow at the mouth and the change in the highest water level at the key section; Step 4: Determine the relationship between flood recurrence period and the change in the highest water level at key sections; in: The relationship between the riverbed deformation and the lowest water level of the key section in step 1 is determined by the following formula: Among them WL dmin (t i ) is the dry season t i The lowest water level of key sections in the year, D riverbed (t i ) is the tth i Annual riverbed deformation value; The WL dmin (t i ) is in m; D riverbed (t i ) is also in m; The relationship between the riverbed deformation in step 2 and the maximum flood flow at the mouth is determined by the following formula: where Q rmax (t i ) is the tth i Maximum tidal flow at the mouth section of the year; The Q rmax (t i ) is in m 3 / s; The relationship between the change in the maximum flood flow at the gate and the change in the highest water level at the key section in step 3 is determined by the following formula: Where ΔWL cmax is the water level change value of the key section, ΔQ rmax is the change value of the maximum tidal flow at the mouth in different selected years; The ΔWL cmax The unit of ΔQ is m; rmax The unit is m 3 / s; The relationship between the flood recurrence period and the highest water level of the key section in step 4 is determined by the following formula: where n p is the current flood recurrence period, WL rmaxb is the highest water level of the key section in the original recurrence period; The n p The unit is year; the WL rmaxb The unit is m.

2. The standard analysis method for riverbed deformation and estuary flooding according to claim 1 is characterized by: In step 1, D riverbed (t i ) Back-silting is a positive value, and down-cutting is a negative value.

3. The standard analysis method for riverbed deformation and estuary flooding according to claim 1 is characterized by: In step 2, Q rmax (t i )The negative sign indicates that the upwelling current is in the opposite direction of the river flow.

4. The standard analysis method for riverbed deformation and estuary flooding according to claim 1 is characterized by: In step 3, ΔQ rmax Take the absolute value, e is the exponent, and the calculation is accurate to 2.7182818.

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