## 4 Results
### Seasonal Evolution Patterns  
In this study, the layer aquaculture regions were separated from the non-aquaculture regions and the sedimentary volume in different elevation intervals was calculated independently. The results show that the seasonal sedimentary evolution patterns of aquaculture regions were more complicated than non-aquaculture regions. From winter 2008 to spring 2009 (the end of the growth period of layer), aquaculture regions of the entire study area were in deposition below \(-100\) cm and in erosion above it. During spring 2009 to summer 2009 (non-growth period), aquaculture regions eroded simply. From summer 2009 to autumn 2009 (the prime growing period), aquaculture regions were in erosion below \(-90\) cm while in deposition above it and were in deposition simply during autumn 2009 to winter 2009 (growth period). In contrast to aquaculture regions, non-aquaculture regions were in erosion from winter 2008 to summer 2009 and in deposition from summer 2009 to winter 2009 (Figure 5a,b). Contrasting the curves of winter 2008 and winter 2009, the aquaculture regions have a demarcation point of \(-40\) cm, where the low tidal flats are in erosion and the high tidal flats are in deposition. However, the variation of the non-aquaculture regions were slight. These results show that the entire study area follows a pattern where low tidal flats were in erosion and high ones in deposition, indicating that the change of scouring and silting caused by layer cultivation was the dominant factor. This result will be expounded specifically in Section 4.3. In addition, the sedimentary evolution patterns of each sandbank is as follows:  
Figure 4: The expansion of the layer aquaculture regions from 1999 to 2013. (**a**)–(**e**) Spatial distribution of the aquaculture regions and (**f**) the growth curve of the area. Figure 5: Seasonal patterns of tidal flats in aquaculture and non-aquaculture regions of the central Jiangsu coast. (**a**,**b**) The entire study area; (**c**,**d**) the Dongsha sandbank; (**e**,**f**) the Liangyuesha sandbank; (**g**,**h**) the Niluoheng sandbank; (**i**,**j**) the Tiaozini, Gaoni and Jianggiiasha sandbanks; and (**k**,**l**) the Zhugensha sandbank. The datum of the water levels is the mean sea level. (1) The Dongsha sandbank (Figure 5c,d). The aquaculture region is principally distributed in the eastern part of this sandbank. The laver growing period is from December to May (from winter to spring), with the aquaculture region undergoing erosion. Both aquaculture and non-aquaculture regions are eroded from spring to summer, while undergoing deposition from summer to autumn. From autumn to winter, the aquaculture region reveals little erosion and the non-aquaculture region exhibits slight deposition. Thus, the sediment volume of both regions during autumn to winter was nearly unchanged. (2) The Liangyuesha sandbank (Figure 5e,f). This sandbank is located in the northern part of the study area with peripherally distributed aquaculture regions. Therefore, the sediment volume variations of the aquaculture and non-aquaculture regions are similar. The laver growth period is from November to June (from autumn to spring). From autumn to winter, the aquaculture and non-aquaculture regions are in deposition while from winter to spring, the two areas experience deposition above \(-50\) cm and erosion below \(-50\) cm. During the non-culture period (from spring to autumn), the aquaculture region is in erosion above \(-70\) cm and in deposition below \(-70\) cm to keep its scouring and silting balance from spring to summer. Simultaneously, the non-aquaculture region experiences moderate siltation within \(-50\)cm\(\sim 0\) cm with sedimentary evolution almost invariable in the remaining elevation ranges. The both two regions erode from summer to autumn and the sediment volume reaches a minimum in the autumn. (3) The Niluoheng sandbank (Figure 5g,h). The sandbank is located in the periphery of the radial sand ridges with minimal area and poor stability.