Friesian湾对海平面上升和地面沉降的形态学响应

MORPHOLOGICAL RESPONSE OF THE FRIESIAN INLET TO SEA-LEVEL RISE AND LAND SUBSIDENCE

Friesina湾是荷兰Wadden海的一个潮汐汊道系统,它由Pinkegat湾和Zoutkamperlaag湾组成。自1986年油气开采以来,在Friesian湾(尤其是Pinkegat湾)出现了地面沉降现象。对于海湾系统的长期大尺度形态发展来说,地面沉降可被认为是短期的相对海平面上升,而目前在该区域其上升速度为每世纪20 cm。海平面的上升会导致潮汐盆地体积增大和潮间带面积缩小,邻近海岸的侵蚀速率也将加快。一个多尺度形态学模型被用于对这些地面沉降产生的影响进行评价,评价结果显示地面沉降可被认为是海平面上升。然而,自油气开采开始后不久便进行的持续监测未能反映模拟得到的影响结果。潮间带的细致测量结果甚至显示沉积速率的增加超过了地面沉降的影响,产生过补偿现象。给出用混合尺度模型模拟Friesian湾对地面沉降的形态学响应的模拟结果,且对地面沉降的影响难以监测的原因作出解释。并尝试用概念模型组合精细过程模型对在潮间带监测到的过补偿现象进行解释。

The Friesian Inlet is a tidal inlet system in the Dutch Wadden Sea. It consists of the Pinkegat inlet and the Zoutkampedaag inlet. Especially in the Pinkegat inlet land subsidence has been taking place due to gas mining since 1986. For the long - term large scale morphological development of the inlet system the land subsidence can be considered as a temporal increase of the relative sea - level rise, of which the present natural value is about 20 cm per century in this area. Increasing rates of sea- level rise will result in an increase of tidal basin volumes and a decrease of inter- tidal areas. Additionally, adjacent coasts will suffer increased erosion rates. These impacts of the land subsidence have been evaluated quantitatively using an aggregated scale morphological model, The model results suggest that the land subsidence can indeed be considered as additional relative sea- level rise. However, the simulated impacts have not been identified by the monitoring which haven been carried out ever since short after the start of the gas mining. Detailed measurements on the inter- tidal fiats even suggest that the sedimentation rate is over - compensating the land subsidence. In this paper we will present the results of the aggregated scale model concerning the morphological response of the Friesian Inlet to land subsidence. Further we will explain why the impacts of the land subsidence are hard to be monitored. We will also attempt to explain the over- compensating phenomenon as monitored on the inter- tidal flats using conceptual model supported by detailed process modelling.