Diagnosis of the Causes of the Rain Flooding in June in the West Africa Coastal Area

Rain flooding during June on the West Africa coastal area is analyzed by using the 95th and 75th percentiles, which represent extreme and intense rainfall events respectively. Thus, the contribution of these events that reaches around 50% shows their impact on the rainfall in June. Atmospheric and oceanic factors influence the rain flooding. Indeed, the extreme events are associated with easterly waves propagating from 20°E, while those of intense events are initiated around 5°E. The impact of oceanic conditions exhibits the warming of the equatorial rail and the Atlantic cold tongue, the warming of the whole ocean basin and a north-south dipole of SST anomalies. The West African monsoon that reaches Abidjan corresponds to a low-level atmospheric flow, whose upward motion extends in latitude from the ocean to the continent. An increase of disturbance contributes to enhancing these events. This is confirmed by the inflow on to the continent of oceanic moisture coming from the ventilation by evaporation of warm water. In addition, the coupled ocean-atmosphere simulations are one of the best candidates that could help to better explain these dramatic events. This study is useful because of showing solutions that could help in adoption of policies for the risks management related to these events.

Geological suitability of natural sponge body for the construction of sponge city——a case study of Shuanghe Lake district in Zhengzhou airport zone

Natural and geological environmental conditions have an important impact on the planning and construction of sponge cities.This paper analyzes geological factors that influence the usage of natural sponge bodies,taking the Shuanghe lake district of Zhengzhou airport zone as an example.An evaluation system with seven factors has been established and the weights of these factors are determined using the analytic hierarchy process(AHP)method.Overlay analysis is then carried out on all factors using GIS to evaluate the geological suitability of the construction of the sponge city.The results show that geologically suitable area for city construction in Shuanghe lake district accounts for 12.3%,relatively suitable area accounts for 76.1%,and relatively unsuitable area accounts for 11.6%.For suitable and relatively suitable areas,we should make full use of the advantages of surface infiltration,vadose zone transportation and aquifer storage to build a sponge city infrastructure with geological engineering as the main component,supplemented by engineering measures such as surface water storage and drainage,and jointly establish a sustainable urban hydrological cycle.For less suitable areas,artificial rain and flood control works,such as roof garden,should be considered.The findings of this paper can serve as an important reference for sponge city planning and construction not only in the research area but also in other regions with similar geological conditions.

Disastrous Rains Downpours and flooding cause more problems for the area hie hard by last year’s earthquake

At least six people were killed on July 25 when a rockslide smashed into a bridge in Wenchuan County,ithe epicenter of last

Prediction of the future flood severity in plain river network region based on numerical model: A case study

Suzhou is one of China＇s most developed regions, located in the eastern part of the Yangtze Delta. Due to its location and river features, it may at a high risk of flood under the climate change background in the future. In order to investigate the flood response to the extreme scenario in this region, 1-D hydrodynamic model with real-time operations of sluices and pumps is established. The rain-runoff processes of the urban and rural areas are simulated by two lumped hydrologic models, respectively. Indicators for a quantitative assessment of the flood severity in this region are proposed. The results indicate that the existing flood control system could prevent the Suzhou Downtown from inundation in the future. The difficulty of draining the Taihu Lake floods should be given attention to avoid the flood hazard. The modelling approach based on the in-bank model and the evaluation parameters could be effective for the flood severity estimation in the plain river network catchment. The insights from this study of the possible future extreme flood events may assist the policy making and the flood control planning.