Method and system for determining coastal erosion disaster early warning lines and calculating spatial scope thereof

A method for determining coastal erosion disaster early warning lines and calculating spatial scope thereof comprises specifically the following steps:

• S1, determining a coastal erosion rate according to coastal erosion change monitoring data and landform data;
• and calculating at least one coastal erosion early warning line in coming N years in conventional conditions according to an established coastal erosion rate calculation method;
• S2, determining the at least one coastal erosion early warning line in N years in extreme conditions by increasing influencing factors of accelerated sea level rise and extreme storm waves and utilizing a determination and calculation method of coastal erosion disaster early warning lines;
• and
• S3, obtaining a coastal erosion retreat position and scope and sending early warning based on the coastal erosion rate in conventional conditions and the at least one coastal erosion early warning line in extreme conditions;
• wherein in the step S1 the established coastal erosion rate calculation method comprises:
• (1) coastal erosion disaster data extraction:
• conducting extraction for data regarding changes of coastal lines and beach corrosion;
• and
• (2) coastal line change rate calculation:
• analyzing temporal changes of positions of the coastal lines by superposition comparison of multi-stage changes of the coastal lines or changes of elevations of mudflats, and calculating the coastal erosion rate in the conventional conditions by end-point methods or linear regression methods;
• wherein in the step (1) coastal erosion disaster data extraction comprises:
• taking cross-section lines perpendicular to the coastal lines as base lines, and reading positions of intersecting points of the base lines with the coastal lines in different periods, or measuring and obtaining distances between the coastal lines and monitoring signs;
• and extraction of the data regarding the changes of beach corrosion comprises:
• taking an intertidal belt or an offshore slope to be a reference, drafting vertical lines downwards, reading respectively positions of intersecting points between the vertical lines and cross-section landform lines in the different periods;
• and in case water depths and landforms are digital elevation model (DEM), and extracting a topographical profile graph by being perpendicular to directions of the coastal lines;
• wherein in the step (2) coastal line change rate calculation comprises:
• determining the multi-stage changes of the coastal lines in different periods and times, when data of the coastal lines or the landform data in less than six stages are collected, calculating the coastal erosion rate by the end-point methods;
• and when the data of the coastal lines or the landform data in six or more stages are collected, calculating the coastal erosion rate by the linear regression methods;
• wherein calculating the coastal erosion rate by the end-point methods comprises calculating the coastal erosion rate in conventional conditions by comparison of position changes taking use of data of the positions of the coastal lines in two different periods, wherein a calculation method is:
• SER
• =
• D
• 1
• -
• D
• 2
• T
• 1
• -
• T
• 2
• ;
• in the above equation, SER means coastal erosion rate, D1 means any of coastal line and bathymetric line or cross-section landform line at a time T1;
• and D2 means any of the coastal line, the bathymetric line or the cross-section landform line at a time T2;
• for the linear regression methods, a one-variable linear best trend line corresponding to all the data is obtained by the least squares method, a rate of slope of the one-variable linear best trend line is the coastal erosion rate in the conventional conditions;
• y is a position of the coastal line, the bathymetric line or the cross-section landform line to be calculated, x is a known initial position of the coastal line, the bathymetric line or the cross-section landform line and a calculation formula of the coastal erosion rate in the conventional conditions are:
• y
• =
• a
• 0
• +
• b
• 0
• ⁢
• x
• ;
• [
• i
• ∑
• x
• i
• ∑
• x
• i
• ∑
• x
• i
• 2
• ]
• [
• a
• 0
• b
• 0
• ]
• =
• [
• ∑
• y
• i
• ∑
• x
• i
• ⁢
• y
• i
• ]
• ;
• in the formula, a0 is a fixed constant and is obtained by one-variable linear intercept calculation;
• b0 is the coastal erosion rate in the conventional conditions;
• i is a number of stages of the data;
• xi2 is a multi-stage least square iterative estimation;
• Xi is a position of the ith stage coastal line, bathymetric line or cross-section landform line and yi a position of the ith stage coastal line, bathymetric line or cross-section landform line to be calculated;
• wherein in the step S2, the method for determining and calculating coastal erosion early warning lines comprises the following steps:
• step 1, determining an initial position of the coastal lines and calculating and determining positions of the coastal erosion disaster early warning lines SN in N years;
• calculating the coastal erosion disaster early warning lines in extreme conditions, which is obtained by calculating the coastal erosion disaster early warning lines in conventional conditions and increasing influencing factors of sea level rise and extreme storm waves;
• step 2, calculating and determining the at least one coastal erosion early warning line SNc under influence of accelerated sea level rise;
• and
• step 3, determining and calculating the at least one coastal erosion early warning line SNc under influence of extreme storm waves.