Sediment supply bottlenecks (2022)

Soil erosion leads to sediment transport through the landscape until sedimentation occurs on land or the sediment flow reaches watercourses, canals or sewers. This data layer shows the points with the highest modelled sediment supply to watercourses of the Flemish Hydrographic Atlas (VHA), canals and sewers, expressed in tonnes of sediment that reaches the water system at this location on average annually. These points together account for 10% of the total annual sediment supply to watercourses of the Flemish Hydrographic Atlas (VHA), canals and sewers. The modelling was carried out with the CN-WS model version 4.2.3 in combination with pycnws version 0.6.3. The calculation was done on a scale of Flanders at a resolution of 20 m. This data layer is an indication of the average sediment supply calculated with an average precipitation erosivity factor of the last 30 years. Scenario A was applied, whereby agricultural parcels are considered grassland when they have a permanent crop cover for at least 2 consecutive years. All other agricultural parcels are considered to be average arable land. The modelling is based on the 2022 agricultural parcel map. The anti-erosion measures implemented in 2022 through management agreements or small-scale anti-erosion works were taken into account. Locally, the modelled values may differ from the real values, as each modelling is only an approximation of reality. Moreover, only the input data that is available and part of the model can be taken into account.土壤侵蚀会引发沉积物在景观中搬运，直至沉积物在陆地沉积，或沉积物流进入河道、运河与下水道。本数据图层展示了佛兰德斯水文图集（Flemish Hydrographic Atlas，VHA）范围内，向河道、运河及下水道输送沉积物量最高的模拟点位，其数值以该点位年均进入水系统的沉积物吨数表征。这些点位合计占佛兰德斯水文图集（VHA）河道、运河及下水道年沉积物总输送量的10%。本次模拟采用CN-WS模型4.2.3版本，结合pycnws 0.6.3版本完成。计算范围覆盖法兰德斯全域，空间分辨率为20米。本数据图层为基于过去30年平均降雨侵蚀力因子计算得到的年均沉积物输送量指示值。本次模拟采用情景A：若农业地块连续两年及以上拥有永久性作物覆盖，则将其归类为草地；其余农业地块均视为常规耕地。模拟基于2022年农业地块地图开展，并纳入了2022年通过管理协议或小型防侵蚀工程实施的侵蚀防治措施。由于所有模拟仅为现实的近似估算，局部区域的模拟值可能与实际值存在偏差。此外，模型仅能纳入已获取的可用输入数据。