Area Ratio of Significant Land Subsidence

The low-lying ground caused by stratum subsidence is prone to rain and flooding. Long-term stagnant water in coastal areas or seawater intrusion into groundwater aquifers can easily lead to salinization of the land and loss of fertility, which affects the value and use of land. Stratum subsidence is an irreversible phenomenon. In order to highlight the efforts of various agencies to prevent and control strata subsidence, the area of significant subsidence is defined as the evaluation index.

地層顯著下陷面積比率

橫軸標籤2

年份（年）

縱軸標籤2

地層顯著下陷面積比率 (%)

指標圖表樣式

stack

Indicator Details

Themes

Sensitive habitats

PSBR model type

Pressure (P)

Corresponding targets

SDGs

15.3 By 2030, combat desertification, restore degraded land and soil, including land affected by desertification, drought and floods, and strive to achieve a land degradation-neutral world

Aichi Biodiversity Targets

Target 15: Protect, restore and promote sustainable use of terrestrial ecosystems, sustainably manage forests, combat desertification, and halt and reverse land degradation and halt biodiversity loss.

Biodiversity Action Plan

D42010 Conduct surveys on the location, area, and scope of the existing degraded ecosystems before 2015, and formulate countermeasures to restore the degraded ecosystems. Key performance indicator of the action plan (the gray background means non-quantitative indicators):

Each agency plans the priority order and methods of restoration of various degraded environments
Restore various degraded environments or areas

Background

The land subsidence makes the low-lying areas easier to flood when it rains, causes long-term accumulation of water in coastal areas or seawater intrusion into the aquifer which can lead to soil salinization and the loss of fertility, affecting the value and utilization of land. Land subsidence is an irreversible phenomenon. To highlight the efforts of various agencies to prevent and control land subsidence, the area of significant subsidence is defined as one of the evaluation indicators.

Definition and Calculation

"Area of significant subsidence" is defined as the area where the subsidence rate exceeds 3cm/year in the benchmark survey data. Subtract the prior elevation of all the leveling rods in the surveying area from the current elevation to obtain the subsidence value and then use the interpolation method to draw the subsidence rate contour map, and use the GIS to calculate the area of the zone within the contours exceeding 3cm/year (the surveying error of benchmark leveling loop is 2cm).

Updates

In 2018, the area of significant land subsidence was 419.6 square kilometers (1.17%). Compared with 2017, there is an increase of 0.07%.

Trends

As the government aggresively promotes the prevention and control of land subsidence, the continuous subsidence rates in subsidence areas have slowed down in recent years. The area of significant land subsidence across Taiwan has decreased from 1,539.1 km² (4.27%) in 2001 to 395 km² (1.10%) in 2017. However, in 2014 and 2015, due to poor precipitatios, the amount of groundwater recharged was less than the amount of groundwater used and evaporated, which caused a more serious land subsidence in the Yunlin area, resulting in an increase in the area ratio of significant land subsidence.

Data Management Authorities

Hydrology Division, Water Resources Agency, MOEA (Minister of Economic Affairs)

Data sources / URL

Groundwater conservation data of the Water Resource Agency, Minister of Economic Affairs

Data Development Status

Data Providers