王飞团队：极端暴雨下小流域洪峰对土地利用景观格局的响应-以中国山东台风“利奇马”暴雨为例

● 水土保持措施可以有效降低洪峰强度和敏感性

SWCMs reduced the flood peak intensity and sensitivities to rainstorm events.

● 通过降低小流域的景观破碎化程度可以提高其应对极端暴雨事件的能力

The ability of small catchments to cope with extreme rainstorms can be improved by reducing landscape fragmentation.

● 水土保持措施降低小流域洪水风险的有效性受到其面积比例的影响

Flood peaks was affected by the area percentage of the conservation measures in the small catchments.

Liu, Y.H. , Han, J.Q., Jiao, J.Y., Liu, B.Y., Ge, W.Y., Pan, Q.B., Wang, F. (2022). Responses of flood peaks to land use and landscape patterns under extreme rainstorms in small catchments - A case study of the rainstorm of Typhoon Lekima in Shandong, China. International Soil and Water Conservation Research, 10(2), 228-239.

DOI:  10.1016/j.iswcr.2021.07.005

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气候变化导致极端暴雨出现的频率和强度增加，山区小流域所面临的极端暴雨洪水风险也随之增加。由于其缺乏大型工程措施，如堤防、大坝和水库，很难通过防洪调度措施减轻洪灾，所以传统的坡面水土保持措施仍然是降低小流域洪水风险的常用办法。另一方面，由于大多数小流域缺乏有效的洪峰流量监测设备，极端暴雨引发的洪水难以观测，水文模型模拟的洪峰数据无法得到验证。坡面尺度的研究无法完全解释土地利用景观格局对流域尺度洪水过程的影响。这些因素限制了我们对极端暴雨事件中小流域洪水过程对土地利用景观格局响应机制的研究。所以 在极端暴雨发生后立即进行实地调查，建立洪水指标与土地利用景观格局指标之间的关系非常重要 。2019年8月10日至8月12日，中国山东省临朐县暴雨中心的场次降雨量高达576 mm。2019年8月14日至8月22日，通过实地调查和室内分析，选取了面积为0.17 km ² ～3.53 km ² 的17个小流域。通过分析洪峰强度、敏感性与土地利用、景观格局指标之间的关系， 主要研究目的如下: (1) 研究洪峰对不同土地利用景观格局的响应机制; (2) 确定调查小流域的洪峰敏感性。

Climate change has resulted in an increase in the frequency and intensity of extreme rainstorms. There has also been an increase in the extreme floods in small watersheds of mountainous. The lack of large engineering measures, such as embankments, dams, and reservoirs, impedes the flood control capacity of small watersheds. Instead, traditional soil and water conservation measures (SWCMs) on slope surfaces, including forest land, grassland, and terraces, are the most common ways to reduce flood risks. Meanwhile, it is difficult to observe floods due to the lack of effective monitoring equipment for flood peak flows in most small watersheds. Flood peak simulated by hydrological models cannot be verified, and studies at the slope scale cannot provide fully explain the effects of land use and landscape patterns on the flood processes at the basin scale. Consequently, this limits our understanding of the effectiveness of land use and landscape patterns on flood in small watersheds during extreme rainstorms. Therefore, it is crucial to conduct field investigations and establish a relationship between the flood indicators and land use and landscape patterns on slope surfaces immediately following rainstorm. As the center of the storm, the county Linqu in the Province of Shandong,China experienced an extreme rainstorm event with a total rainfall of 576.00 mm from August 10, 2019, through August 12. A detailed investigation of the rainstorms during Typhoon Lekima in Shandong Province, was conducted from August 14, 2019, through August 22 via field surveys and indoor analysis. In this survey, a total of 17 small catchments with an area of 0.17 km ² –3.53 km ²  were selected from the research area. Through analyzing the relationship between flood peak intensity, sensitivity and land use, landscape patterns, the main objectives are as follows: (1) to investigate the response mechanisms of flood p eaks to dif ferent land use landscape patterns; (2) to examine the sensitivities of local small catchments to flood peaks.

图1 研究区位置图

Fig. 1. Location of the study area.

● 洪峰数据是通过实地调查小流域沟道的洪痕、地形和糙率，然后通过曼宁公式计算得到的。在极端暴雨洪水事件发生后，立即开展实地调查，所测量的沟道断面选择在小流域的沟道出口位置，采用洪痕法测量最大的过水面积。对断面所在沟道左右岸洪痕位置进行测量宽度，然后对于宽度小于3.0m的沟道每隔0.5m测量一次深度，对于宽度大于3.0m的沟道每隔1.0m测量一次深度。

Flood peak data were obtained on the basis of the calculation of flood benchmark, terrains and the roughness coefficient of channels by means of a field survey. After the cross section was confirmed, the flood peak was calculated using Manning's equation below. A field investigation was launched immediately after the flood event. The cross-sections were selected at the exit of the investigate channel, and the maximum flood level at each cross-section was based on flood benchmark. The field measurements were performed on the cross-sections. If the width was less than 3.0 m, the depth of the corresponding channel would be measured at an interval of 0.5 m. If the width greater than 3.0 m, the depth would be measured every 1.0 m.

图2 测量洪痕断面，(a)、(b)、(c)分别表示不同沟道的洪痕断面，红线代表洪痕，(d)为实际测量现场

Fig. 2. Measure flood benchmark cross-section. (a), (b) and (c) represents flood benchmark of different cross-section, the red line represents the flood benchmark. (d) Is for field measurement.

● 洪峰模数与林草地比例、梯田比例呈显著的负相关关系 ( p＜0.05 )；与坡耕地比例呈显著的正相关关系 ( p＜0.05 )。 洪峰模数与斑块平均大小 ( MPS )、蔓延度指数 ( CONTAG )、聚集度 ( AI ) 呈负相关关系，与香农多样性指数 ( SHDI )、香农均匀性指数 ( SHEI )、斑块密度 ( PD ) 、景观分割度 ( DIVISION ) 呈正相关关系。

The flood peak modulus forms a significantly negative correlation with the proportions occupied by forest-grassland and terraces (p < 0.05), but a significantly positive correlation with that of sloping cropland (p < 0.05). The flood peak modulus is negatively correlated with Mean patch size (MPS), Contagion index (CONTAG) and Aggregation index (AI) but has a positive correlation with Shannon's diversity index (SHDI), Shannon's evenness index (SHEI), Patch density (PD) and Landscape division index (DIVISION).

● 洪水指数 K 与林草地比例和梯田比例呈负相关关系，与坡耕地比例显著正相关关系 ( p＜0.05 )。 洪水指数 K 与斑块平均大小 ( MPS ) 、蔓延度指数 ( CONTAG ) 、聚集度 ( AI ) 呈负相关关系，与香农多样性指数 ( SHDI ) 、香农均匀性指数 ( SHEI ) 、斑块密度 ( PD ) 、景观分割度 ( DIVISION )   呈正相关关系 。

The flood index K of the small catchments in the three groups are negatively correlated with the proportions covered by forest-grassland and terraces but positively correlated with those of sloping cropland (p < 0.05). The flood index K of small catchments in the three groups forms a negative correlation with MPS, CONTAG and AI. However, the index is positively correlated with SHDI, SHEI, PD and DIVISION.

● 在本次调查中，洪水指数从 3.61 到 4.55 ，平均值为 4.05 。 2017 年 “7.26” 岔巴沟极端暴雨研究中，洪水指数 K 的平均值为 4.0 ，本研究计算出的平均 K 值与之基本相同。 参考其他学者的研究，本研究中小流域对洪水的敏感性可评价为“适中的”。

In this survey, the flood index K of different catchments was calculated, with a range of 3.61–4.55 and an average of 4.05. According to the research on the “7.26” Chabagou extreme rainstorm of 2017, the average K value is determined to be 4.0, which is basically the same as the calculated K value in this study. With reference to the studies conducted, the sensitivity of small catchments to floods can be evaluated as moderate.

图3 本研究中小流域洪水指数K与其他研究对比

Fig. 3. Comparison chart of the flood index K values in Bryndal, Fu and this study.

● 研究发现， 水土保持措施降低小流域洪水风险的有效性主要受到其面积比例的影响，小流域洪峰模数和洪水指数K均随着景观破碎化程度的增加而增加。 为了提高小流域应对极端暴雨的能力，可以增加流域内林地、草地和梯田的面积比例，同时减少其景观破碎化程度。

Flood peaks was dominated by the area percentage of the conservation measures in the small catchments. It is found that both the flood peak modulus and flood index K of catchments in the research area increase with increasing landscape fragmentation.  To improve the ability of small catchments to cope with extreme rainstorms, we can increase the areas of forest-grassland and terrace while reducing the fragmentation of their landscape.

刘元昊， 西北农林科技大学水土保持研究所博士研究生，主要研究方向为森林水文学与极端暴雨。

联系方式： Liuyuanhao998@163.com

Liu Yuanhao, Ph.D Student of Institute of Soil and Water Conservation, Northwest A&F University，mainly focuses on: Forest hydrology and extreme rainstorm.

Contact information: Liuyuanhao998@163.com

             

王飞， 中国科学院水利部水土保持研究所，西北农林科技大学水土保持研究所研究员，主要研究方向为区域水土保持与环境。

联系方式： wafe@ ms.iswc.ac.cn

Wang Fei,  Professor of Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Institute of Soil and Water Conservation, Northwest A&F University, the main field is regional soil and water conservation and environment.

Contact information: wafe@ ms.iswc.ac.cn

极端暴雨 ; 洪峰强度 ; 洪 峰敏感性 ; 土地利用 ; 景观格局

Extreme rainstorm; Flood peak intensity; Flood peak sensitivity; Land use; Landscape pattern

Sterk, G.(2021).A hillslope version of the revised Morgan, Morgan and Finney water erosion model. International Soil and Water Conservation Research, 9(3), 319-332.    

https://doi.org/10.1016/j.iswcr.2021.01.004

Li, Y. , Satyanaga, A. ,  Rahardjo, H.(2021).Characteristics of unsaturated soil slope covered with capillary barrier system and deep-rooted grass under different rainfall patterns. International Soil and Water Conservation Research, 9(3), 405-418.    

https://doi.org/10.1016/j.iswcr.2021.03.004

Didoné, E.J. , Minella, J.P.G. , Piccilli, D.G.A. (2021). How to model the effect of mechanical erosion control practices at a catchment scale?. International Soil and Water Conservation Research, 9(3), 370-380.    

https://doi.org/10.1016/j.iswcr.2021.01.007

Wang, C. , Shan, L. , Liu, X. , Yang, Q. , Cruse, R. M. , Liu, B. , Li, R. , Zhang, H. , Pang, G.(2020).Impacts of horizontal resolution and downscaling on the USLE LS factor for different terrains. International Soil and Water Conservation Research, 8(4), 363-372.    

https://doi.org/10.1016/j.iswcr.2020.08.001

Hatefi, M. , Sadeghi, S. H. , Erfanzadeh, R. , Behzadfar, M. (2020).Inhibiting soil loss and runoff from small plots induced by an individual freeze-thaw cycle using three rangeland species. International Soil and Water Conservation Research, 8(3), 228-236.    

https://doi.org/10.1016/j.iswcr.2020.05.004