METHOD FOR PREVENTING REPEATED (TSUNAMI, STORM SURGE, AND RIVER) DISASTERS BY FORCES OF NATURE

Abstract

Provided is a technique for preventing repeated river, storm surge, and tsunami disasters. “Sea hollow (UTSURO)” is constructed at an estuary, violent tide is generated in an estuary basin water area of a river, ebb and flow energy is caused to exceed flow energy due to gravity in a downstream part of the estuary flow are conventionally dominated by the flow energy due to gravity, the flow energy in the river is thus redistributed to deeply dig the riverbed, enhance flood discharge ability, and prevent repeated river disasters, a levee body of the “sea hollow (UTSURO)” is shared, tsunami or storm surge is reflected in a coastal sea area and is prevented in the sea area, tsunami or storm surge invading the estuary, or estuary flood is caused to overflow into an upstream migration water path constituting the “sea hollow (UTSURO)”, and peak cut thereof is performed.

Claims

1-8. (canceled)

9. A method for preventing repeated river disasters, comprising: surrounding with a levee body a part of an area with a water level variable due to tide levels to form a surrounded water area; connecting, to the surrounded water area, a water channel for putting river water and water from a sea in and out of the surrounded water area; configuring the water channel so that one end portion of the levee body is connected to one of a riverside of a river or a coast proximate to an estuary and so that an other end portion of the levee body is in the river and forms a water inlet and outlet of the water channel such that water from the river and seawater flow into the surrounded water area from the water inlet and outlet at a time of a high tide level and the river water and the seawater inside the surrounded water area flow out of the water inlet and outlet to the river at the time of a low tide level, thereby scouring sediments at a bed of the river on a downstream side from the water inlet and outlet, wherein a position of the water inlet and outlet of the channel is changed in a direction of flow of the river by varying a length of the other end portion of the levee body.

10. The method for preventing repeated river disasters according to claim 9, wherein a plurality of sectioned water channels are formed in the river with a plurality of separation levees extending in the river flowing direction, and movable dams are placed on both end portions of each of these sectioned water channels in the river flowing direction, such that an amount of flowing water in each sectioned water channel is able to be changed through an operation of opening or closing each of the movable dams.

11. The method for preventing repeated river disasters according to claim 9, wherein a portion of the levee body facing the sea comprises a breakwater, and a seabed in front of the breakwater is formed such that the water depth in an area of the sea in front of the breakwater is equal to or greater than double a height of a wave of a tsunami.

12. The method for preventing repeated river disasters according to claim 11, wherein the surrounded water area is provided on each of both left and right sides of the estuary, and an estuary width of a further estuary formed between breakwaters of the surrounded water areas on both the sides is set to be a minimum width necessary for releasing the river water.

13. The method for preventing repeated river disasters according to claim 9, wherein the levee body comprises a plurality of gaps, a purification water area is surrounded by the levee body, and the levee body's position is connected to the river proximate to the estuary.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0080] FIG. 1 is a vertical sectional view illustrating energy sections of a river flow.

[0081] FIG. 2 is a plan view at an estuary of a system that generates violent tide at a river estuary part.

[0082] FIG. 2-1 is a sectional view along D-D in FIG. 2.

[0083] FIG. 2-2 is a sectional view along E-E in FIG. 2.

[0084] FIG. 2-3 is a sectional view along F-F in FIG. 2.

[0085] FIG. 2-4 is a diagram illustrating a flood water flow direction during flood in the left diagram and representing a water flow direction at the time of ebb tide during flood in the right diagram.

[0086] FIG. 2-5 is a diagram representing a water flow direction at the time of invasion of tsunami or storm surge in the left diagram and representing a water flow direction at the time of ebb tide in the right diagram.

[0087] FIG. 3 is a system diagram of riverbed scouring in a water area dominated by flow energy due to gravity at a river upstream part.

[0088] FIG. 3-1 is a sectional view along K-K in FIG. 3.

[0089] FIG. 3-2 is a sectional view along J-J in FIG. 3.

[0090] FIG. 3-3 is a plan view of sequentially performing riverbed scouring from the downstream in FIG. 3.

[0091] FIG. 4 is a plan view of a method for generating violent tide using an old river channel in an estuarine basin as an upstream migration channel and it is possible to generate violent tide at an estuary by surrounding and closing an estuary sea area such as a diversion channel or a branch river by 8, and opening it at the upstream of a mainstream river using a water channel as 19.

REFERENCE SIGNS LIST

[0092] 1 Height of river levee [0093] 2 Ground height of riverbed of river in current situation [0094] 3 Surface water at normal time [0095] 4 Riverbed of river in current situation [0096] 5 Maximum flood level [0097] 6 High water level of ebb and flow [0098] 7 Low water level of ebb and flow [0099] 8 Tsunami breakwater [0100] 9 Levee body constituting upstream migration channel, overflow levee for peak-cut at time of attack of river upstream migration tsunami, storm surge, and estuary flood [0101] 10 Vertical section of estuary riverbed scoured by tide generation apparatus “hollow sea (UTSURO)” [0102] 11 Direction of lowering of riverbed of scoured riverbed at estuary due to stable slope of river [0103] 12 Scoured riverbed with stable slope of 11 [0104] 13 Extension direction of levee body constituting upstream migration channel [0105] 14 Leading end scouring by vortex flow at turnaround of upstream migration channel entrance [0106] 15 Vertical section of riverbed scouring with decrease in stable slope in case of extension toward upstream of levee body constituting upstream migration channel [0107] 16 Direction of decrease in stable slope at upstream of river with extension of upstream migration channel [0108] 17 HHWL decrease line with enlargement of flood discharge section due to lowering of riverbed accompanying 15 described above [0109] 18 Direction of river flow [0110] 19 Upstream migration channel [0111] 20 Direction of peak-cut due to upstream migration tsunami or storm surge of river or overflow of river flood [0112] 21 Returning flow of 20 described above due to change in ebb and flow [0113] 22 Direction of tsunami [0114] 23 Reflection of tsunami [0115] 24 Direction of tsunami or storm surge flow [0116] 25 Returning flow of 24 described above [0117] 26 Inland water area of “sea hollow (UTSURO)” B [0118] 27 Sediment trap outer levee constituting “sea hollow (UTSURO)” [0119] 28 Tsunami and storm surge invasion preventing levee [0120] 29 Sediment trap of “sea hollow (UTSURO)” [0121] 30 Inner levee constituting “sea hollow (UTSURO)” [0122] 31 Tsunami wave height [0123] 32 Calm water level of tsunami wave [0124] 33 Expanded water area of “sea hollow (UTSURO)” [0125] 34 Highly purification system using “sea hollow (UTSURO)”

REFERENCE SYMBOLS LIST

[0126] LR River extension [0127] Lm Altitude [0128] Lr Entire length of river [0129] Lt01 Extension of overflow levee of initial upstream migration channel [0130] Lv1 Extension of deeply-scoured water area due to returning flow (leading end vortex flow) with placing of upstream migration channel [0131] Lt02 Extension of overflow levee obtained by extending deeply-scoured water area toward upstream [0132] Lv2 Vortex flow length at leading end of overflow levee Lt Extension of river water area dominated by ebb and flow energy [0133] Ln Extension of water area dominated by flow energy due to gravity [0134] B1, B2, and B3 are levee bodies constructed by collecting mainly riverbed sediments in river reservation and longitudinally successively constructing low separation levees, [0135] G1, G2, and G3 are movable dams placed on left and right sides of upstream and downstream every time longitudinal upward and downward movement by 1 to 5 m occurs.