Rehabilitation of a debris-flow prone mountain stream in southwestern China – Strategies, effects and implications

Basic information

• Case ID: INT-180-1
• Intervention type: Created habitats
• Intervention description:

  Article talks about rehabilitation of a creek in China, which is debris prone. The issue is primarily anthropogenic in nature but it is driven also by climatic factors (i.e. the landslides/erosion risk is both anthropogenic and climatic). As a whole the intervention integrated a variety of engineering, biological, and social intervention. In areas subjected to serious gully erosion, small and medium-sized check dams, guiding dikes, and reforestation of fast-growing and effective erosion-controlling species were applied to control erosion and sediment transport, and to stabilize hillslopes and stream channels. In areas subjected to moderate soil erosion, hillslopes were modified by terracing fields and cultivation of plant species for soil and water conservation. In contrast, areas with gentle soil erosion were managed by closing hills to allow ecosystems to self-regenerate Initially engineering measures such as checkdams were applied, then reforestation with an introduced exotic species L leucocephala L. leucocephala was introduced to enhance the development of riparian vegetation along the creek. The introduced vegetation is characterized as a forest in the article. The application of rehabilitation measures over the past 30 years has stabilised the stream channel and the slope of Shengou Creek. Riparian vegetation has been well-established, sharply reducing soil erosion and sediment transport. erosion control was effective, and reduced sediment flow created channel bed scouring, they therefore developed step-pool systems to mitigate this. Riparian vegetation has developed well along the channels, enhancing valley floor roughness and local aesthetics (Fig. 6c and d). By 2005, the creek had been transformed from a debris flow gully into a recreational area with beautiful step-pool morphology and riparian forest, now becoming a forest park for local inhabitants.

• Landscape/sea scape ecosystem management: Yes

• Climate change impacts	Effect of Nbs on CCI	Effect measures
  Mudslides / Landslides	Positive	Same outcome measure for both soil erosion and mudslide reduction Sediment concentration (indicator of sediment supply from hillslopes/upstream channels); as an indicator of sediment related hazard/debris flow/landslide, and gully erosion
  Soil erosion	Positive	Same outcome measure for both soil erosion and mudslide reduction Sediment concentration (indicator of sediment supply from hillslopes/upstream channels); as an indicator of sediment related hazard/debris flow/landslide, and gully erosion

• Approach implemented in the field: Yes
• Specific location:

  Shengou Creek the upper Yangtze River; Xiaojiang River basin; Yunnan–Guizhou Plateau

• Country: China
• Habitat/Biome type: Created forest |
• Issue specific term: Not applicable
  

Evidence

• Notes on intervention effectivness: Quasi experimental study; compares intervention site with two control sites Ultimately, the intervention is a hybrid, or integrated landscape approach, however the authors specifically delineate the impact of the introduced L. leucocephala plants and state “ Riparian vegetation has been well-established, sharply reducing soil erosion and sediment transport. The basic characteristics of the tree layer community structure for tree ages of 4, 10, and 20 years of L. leucocephala introduced into the Shengou Creek basin are summarized in Table 2” “Following the increase of forest stand age and coverage, soil erosion from the hillslopes was drastically reduced. In addition, it is noticeable that herb and litter layers enhanced soil structure and raised the infiltration capacity for rainwater, thereby slowing the velocity of overland flow and reducing soil erosion. Furthermore, it is observed the soil layer developed on the previously barren slopes accumulates humus, enhancing vegetation growth while diminishing rates of soil erosion.” For ecosystems outcomes mixed was entered – while the measures were better in the rehabilitated creek then in the non-intervention sites, mixed was coded because in the discussion they report " Negative byproducts include the limited and homogenous species composition of L. leucocephala forests, as it hinders other plants species to develop, negatively influencing ecological diversity in the planting area”
• Is the assessment original?: Yes
• Broadtype of intervention considered: Not applicable
• Compare effectivness?: No
• Compared to the non-NBS approach: Not applicable
• Report greenhouse gas mitigation?: No
• Impacts on GHG: Not applicable
• Assess outcomes of the intervention on natural ecosystems: Yes
• Impacts for the ecosystem: Mixed
• Ecosystem measures: benthic macroinvertebrate, biomass per unit area, taxa richness, habitat diversity index above ground – “Vegetation development was investigated during 2006–2008 using sample plots. The size of each plot is 10 m 10 m. For artificial forests with tree ages of 4, 10, and 20 years, 3–5 plots were chosen in the middle of each artificial forest so as to represent the developmental condition of the forest and to reduce error due to the relatively small size of the plots. Species diversity and community structures of tree layers, secondary shrub layers, and herbaceous layers were analyzed to derive indices of species richness, coverage, and importance value"
• Assess outcomes of the intervention on people: No
• Impacts for people: Not reported
• People measures: n/a
• Considers economic costs: No
• Economic appraisal conducted: No
• Economic appraisal described:
• Economic costs of alternative considered: No
• Compared to an alternative: Not reported

Evaluation methodology

• Type of data: Quantitative
• Is it experimental: Yes
• Experimental evalution done: In-situ/field
• Non-experimental evalution done: Not applicable
• Study is systematic: