Stability Of Forefront Seabed At The Hangzhou Bay’s North Shore And Its Pact On Seawall’s Safety

Coastal zone is an important regional gathering of the social and economic activities. Over the last decades, coastal and ocean engineering was rising. Coastal and marine engineering gets the land and sea convenient transportation, but also faces danger and abuse from the sea. The seawall is the main barrier for protection of coastal and marine engineering. The seawall’s security is the main indicators of the coastal and marine engineering’s security. The stability of coastal sea-bed and seawall security has a clear link. Therefore, in order to protect the marine engineering, research of seabed stability and seawall security is imminent.Based on the seawall management project "Shanghai Jinshan Petrochemical hydrological tests (2011-2012years)" commissioned by Sinopec Shanghai Petrochemical Company Limited and "Shanghai Petrochemical former seabed stability and seawall early warning (2007-2012years),Shanghai Water Transportation Design Research Ltd commissioned project "Shanghai Harbor City tourism project shoreline stability consulting research (2011-2012years)", the paper selects the north shore of Hangzhou Bay-Nanhuizui, Luchaogang and Jinshanwei three typical coast as targeted research area. Different years’measured sea-bed topography data is collected. ArcGIS as a basic technical support is dopted. Seabed clustering exponential growth model is used to predict future. The overall analysis, with some combination of different perspectives, different levels and at different spatial scales, a comprehensive and systematic study is put on the stability of the seabed and on the seawall’s security, which improve stability of the seabed and seawall security path and research framework. Overall, this article is mainly carried out the following research and obtains the corresponding conclusion.1. A comprehensive analysis of the overall stability on status of the three study area’s seabed. The analysis found that:(1) The whole sea-bed is stable.(2) At20st century the stability of Nanhuizui Dongtan’s sea-bed is better, which improve safety of the seawall. When the21st century comes, accretion continues to happen. The sea-bed is at unstable state; The seabed of South Beach is always extreme instable.(3) Before the year of1998Luchaogang sea-bed’s stability is poor with continuous accretion. After the year of1998overall stability of sea-bed is increasing.(4) The stability of Jinshanwei seabed sharply declines after the causeway project is completed.2. Predicts the2013waters seabed topography:(1) North of the Nanhuizui is taken by minor siltation, southern and eastern by erosion.(2) Luchaogang west seabed erodes, with siltation and erosion alternating banded; accretion controls eastern.(3) Most of Jinshan deep groove eroded. The southern sea-bed will be taken by accretion. The western sea-bed maintains the erosion and deposition balance.3. After analysis of typical coast seawall’s security level, studies have shown that:(1) Safety of seawall declines from north and south towards middle of Nanhuizui.(2)Safety of seawall declines from west towards east at Luchaogang’s eastern.(3) Jinshanwei seawall security of the three profiles emerged in the downward trend.(4)In the future of2013, distribution’s characteristics of seawall’s safety keep old.