Characteristics of geological hazards in South China coastal areas and impact on regional sustainable development
Prevention and treatment of geological hazards is important for the sustainable development of human society. Surface geological hazards alone caused direct economic losses of ¥3.47 billion, with 768 deaths and 785 injuries in Guangdong Province, South China, from 1994 to 2005. The major factors causing geological hazards can be categorised into three types: geo-environmental, climatic-meteorological and human activity. Accompanied by rapid economic development and population growth, human activities can cause geological hazards that are as serious as those caused by natural factors. The authors propose some suggestions for prevention and treatment of geological hazards to achieve sustainable development on the Chinese coast.
SOIL EROSION AND CONSERVATION IN YUNNAN PROVINCE, CHINA
The scale and severity of soil erosion within the headwaters of the Yangtze River in Yunnan Province are discussed. The Yangtze River rises in the western uplands of the Qinghai-Tibet Plateau and traverses 6380 km through southern and central China. The headwaters are in tectonically active and geologically unstable uplands. The basin is also generally under intensive agricultural use, mainly for rice cultivation. Hence, erosion rates are high and of increasing concern, especially considering the construction of the Three Gorges (Sanxia) Dam in the middle section. Sedimentation within the proposed reservoir could impair its efficiency and therefore soil conservation must be an integral component of basin management. Soil conservation efforts in Yunnan are reviewed and the local-scale planned approach to soil conservation is illustrated, using Dongchuan and Xundian as case studies. An ongoing runoff plot study at Yunnan Agricultural University (Kunming) is used to evaluate the effectiveness of various soil conservation measures. Maize (Zea mays) cropping treatments, typically employed in local agronomic practices, are applied to 30 erosion plots at 3 different slope angles, cultivated both parallel and perpendicular to the contour, thus simulating a range of agricultural conditions on arable slopes. Plot data from 1993-1996 suggest several suitable soil conservation measures. Erosion rates were generally lower on plots where contour cultivation was used. The mean contour cultivation erosion rate was 0.69 of the mean downslope orientated cultivation rate. Straw mulch and contour cultivation seem particularly suitable soil conservation measures. INTRODUCTION
Sedimentary evolution of the Pliocene and Pleistocene Ebro margin, northeastern Spain
Abstract The Pliocene and Pleistocene deposits of the Spanish Ebro margin overlie a regional unconformity and contain a major disconformity. These unconformities, named Reflector M and Reflector G, mark the bases of two seismic sequences. Except for close to the upper boundary where a few small channel deposits are recognized, the lower sequence lacks channels. The upper sequence contains nine channel-levee complexes as well as base-of-slope aprons that represent the proximal part of the Valencia turbidite system. Diverse geometries and variations in seismic units distinguish shelf, slope, base-of-slope and basin-floor facies. Four events characterize the late Miocene to Pleistocene evolution of the Ebro margin: (a) formation of a paleodrainage system and an extensive erosion-to-depositional surface during the latest Miocene (Messinian), (b) deposition of hemipelagic units during the early Pliocene, (c) development of canyons during the late Pliocene to early Pleistocene, and (d) deposition of slope wedges, channel-levee complexes, and base-of-slope aprons alternating with hemipelagic deposition during the Pleistocene. Sea-level fluctuations influenced the evolution of the sedimentary sequences of the Ebro margin, but the major control was the sediment supply from the Ebro River.