Damage of check dams by extreme rainstorms on the chinese loess plateau: A case study in the Chabagou watershed

Abstract

Check dams are widely distributed and abundant on the Chinese Loess Plateau and play an important role both in reducing damage from flash floods and in retaining sediment. Some check dams are destroyed either partially or fully during rainstorms.The investigation of the actual damage caused to check dams as a result of specific rainstorm floods is of great value for analyzing their effects and failure modes, and is also helpful for proposing a reasonable approach for their improvement.The “7.26” extreme rainstorm event on July 25 and 26, 2017, in Yulin in northern Shaanxi Province, China, resulted in serious infrastructural damage and economic losses.This study reports on a detailed investigation undertaken between August 27 and October 28, 2017, of the causes and severity of the damage to the check dams in the Chabagou watershed.The results showed that out of a total of 572 check dams surveyed, 63.6% were destroyed and 9.3% were damaged.The mean dam opening was 4.8 m wide and 3.4 m deep, while the mean water culvert was 1.7 m wide and 2 m deep.The main causes of the damage were as follows: (1) the flood return period exceeded the dam design standards, (2) 94.1% of the check dams lacked a spillway, and (3) the main land use types on the check dams were farmland and bare soil. Based on the findings of this study, the following recommendations are made: (1) improve the existing design standards for check dams, (2) build additional spillways and maintain existing spillways in a timely fashion, and (3) encourage the development of natural grass and shrub land as the best land use type on check dams.