Open access peer-reviewed chapter

# Flood Damage Reduction in Land Subsidence Areas by Groundwater Management

By Yin-Lung Chang, Jinn-Chuang Yang, Yeou-Koung Tung, Che-Hao Chang and Tung-Lin Tsai

Submitted: June 11th 2018Reviewed: August 2nd 2018Published: November 5th 2018

DOI: 10.5772/intechopen.80665

## Abstract

Continuing land subsidence can diminish the effectiveness of an existing flood mitigation system and aggravate the flood hazard. This chapter demonstrates that, through groundwater management with an effective pumping scheme, flood hazard and related flood damage in land subsidence area can be reduced. The chosen study area is in the southwest coast of Taiwan, which has long been suffering from frequent and wide-spread flooding primarily due to land subsidence induced by groundwater overpumping. Numerical investigation in the study area clearly shows that effective management of groundwater pumping can play an important role in long-term sustainable solution for controlling the spatial-temporal variability of future land subsidence, preventing the flood hazard from worsening, reducing the flood damage, and satisfying the groundwater demand.

### Keywords

• flood hazard
• flood damage reduction
• risk analysis
• groundwater management
• land subsidence

## 4. Conclusions

Groundwater is an important source of water supply, especially in regions where surface water supply is insufficient or not stable. However, the lack of proper management for groundwater extraction and usage in land subsidence prone areas could create a number of undesirable consequences such as damaging building structures, aggravating flood inundation hazards, and diminishing effectiveness of flood control facilities. This chapter presents a methodological framework demonstrating how a subsidence-focused GWM model can be formulated and applied to obtain an optimal pumping strategy that reduces the negative impact of land subsidence in a coastal region in western Taiwan which is experiencing serious land subsidence and associated flood hazards. Numerical results clearly show that, through the use of an optimal GWM model with an explicit consideration given to subsidence control, one is able to ease off uneven land surfaces and reduce seriousness of land subsidence and flood damage as well as sustain the flood protection level of drainage systems by maintaining a suitable freeboard. All these features provide strong evidence that GWM can play an important role, along with other engineering measures, in providing a sustainable solution to flood inundation problem in land subsidence prone areas.

## Acknowledgments

This study was support by the Water Resources Planning Institute, Water Resources Agency, Ministry of Economic Affairs of Taiwan.

## Conflict of interest

No potential conflict of interest is present in this chapter.

## Nomenclature

B

layer thickness

EBt

expected FDR benefit by GWM in Year-t

g

gravitation acceleration

i

interest rate

InunDmgTw/GWMt

inundation damage in the study area with GWM while subject to the T-year rainstorm

InunDmgT,w/oGWMt

inundation damage without GWM while subject to the T-year rainstorm

kuc

the kuc-th control point outside the near-shore low-lying area

kc

the kc-th control point within the near-shore low-lying area

NC

number of control points inside near-shore low-lying area

NL

number of layers in groundwater aquifer

NP

number of pumping wells

NT

number of groundwater management period

NUC

number of control points outside near-shore low-lying area

Qjt

pumping rate at the j-th well during the t-th time period

QDt

groundwater demand during the t-th time period

QLjt

minimum pumping rates at the j-th well during the t-th time period

QUjt

maximum allowable pumping rates at the j-th well during the t-th time period

UGPW

α

the ratio of elastic to inelastic compaction per unit increase in drawdown

sl,k,t

land subsidence within layer-l at point-k during the t-th time period

hl,k,t

drawdowns of layer-l, point-k at the end of the t-th time period

ρw

density of water

hl,k,tp

difference between initial head and preconsolidation head at the end of the t-th time period

Δs(•)

cumulated land subsidence at control points at the end of the management period

Δs*(•)

maximum allowable land subsidence at control points at the end of the management period

μ, λ

Lame constants

## How to cite and reference

### Cite this chapter Copy to clipboard

Yin-Lung Chang, Jinn-Chuang Yang, Yeou-Koung Tung, Che-Hao Chang and Tung-Lin Tsai (November 5th 2018). Flood Damage Reduction in Land Subsidence Areas by Groundwater Management, Recent Advances in Flood Risk Management, John Abbot and Andrew Hammond, IntechOpen, DOI: 10.5772/intechopen.80665. Available from:

### Related Content

#### Recent Advances in Flood Risk Management

Edited by John Abbot

Next chapter

#### Evidence-Based Contingency Planning to Enhance Local Resilience to Flood Disasters

By Miho Ohara, Naoko Nagumo, Badri Bhakta Shrestha and Hisaya Sawano

First chapter

#### Introductory Chapter: Australia—A Land of Drought and Flooding Rain

By John Abbot

We are IntechOpen, the world's leading publisher of Open Access books. Built by scientists, for scientists. Our readership spans scientists, professors, researchers, librarians, and students, as well as business professionals. We share our knowledge and peer-reveiwed research papers with libraries, scientific and engineering societies, and also work with corporate R&D departments and government entities.

View all Books