2006 — Suggestions on Flood Control Embankment Construction for the Lishui River Scenic Belt (Part 1)
Design the embankment project with new concepts so that it serves three major functions: flood control, ecology, and landscape — Suggestions on Flood Control Embankment Construction for the Lishui River Scenic Belt. Preface: The so-called "Lishui River Scenic Belt" specifically refers to the Lishui River waters and the riverside areas on both banks from Mulongtan Dam upstream to Hongbiyan Dam downstream in the urban area. Among these, the section from the right side of the southern end of the Lishui Bridge to Ganxi, and the Guanyin Bridge
This article has been compiled from historical materials in the "Zhangjiajie Tour Guide Network" (33519.com · City Overview section). Some administrative divisions, population, socioeconomic data, and policy information may be outdated and are for reference only; for the latest situation, please refer to official releases by the local government and scenic areas.
Designing embankment projects with new concepts so that they combine the three major functions of flood control, ecology, and landscape—Suggestions on the construction of flood-control embankments for the Lishui Scenic Belt
Preface
The so-called "Lishui Scenic Belt" specifically refers to the Lishui River waters and the riverside sections on both banks within the urban area, from the Mulongtan Dam upstream to the Hongbiyan Dam downstream. Among these, the flood-control embankment projects have already been completed successively in the section from the right side of the southern end of the Lishui Bridge to Ganxi, and in the sections from the left side of the northern end of the Guanyin Bridge to Baotagang and from the right side to Shoujinyan; other sections have been listed by the municipal government as projects to be built in the near future. Therefore, the following suggestions are hereby made to the municipal government:
First, avoid the continued occurrence of the disconnect between embankment project construction and the planning and construction of the Lishui Scenic Belt, and incorporate them together into the Lishui Scenic Belt for overall consideration, planning, and construction;
Second, it is necessary to change the mindset of embankment project construction that takes flood control as the sole purpose; flood-control embankments should simultaneously possess flood-control functions, ecological functions, and landscape functions.
With scientific progress, people have come to realize that water conservancy projects may cause varying degrees of negative impact on river ecosystems. This is especially true of embankment projects whose sole purpose is flood control, because insufficient attention to environmental effects and ecological compensation leads to the artificial channelization of natural rivers, including the straightening of river morphology, the geometric regularization of river cross-sections, and the hardening of embankment materials, among others. Today, as urban ecological environments increasingly attract attention, embankment project construction entering urban river sections undoubtedly faces an urgent issue that must be solved, namely that on the basis of a single flood-control function, ecological construction content must be added. The urban area of Zhangjiajie City is being built as a landscape tourism city and tourist destination matching the Wulingyuan core scenic area; the Lishui River that runs through the city is undoubtedly an extremely important landscape axis of this city and an important carrier for shaping the city's character and spirit. Therefore, in addition to flood-control and ecological functions, its embankment projects should also possess landscape functions. Article 85 of the Master Plan of Zhangjiajie City states: "The development and regulation of the Lishui River should, on the premise of ensuring its flood-discharge function, also take into account such functions as greening, tourism, landscape, and riverside transportation." Unfortunately, the two completed sections of flood-control embankments have committed the taboo of artificially channelizing a natural river, thereby neglecting the existence of biological communities around the river. The tall, rigid concrete embankments artificially block people's accessibility to the water. In short, they lack the ecological functions they should have and the landscape functions required by the city's Master Plan, which calls for integrating tourism and leisure. In view of this, how to build the remaining flood-control embankments without repeating the old mistakes is undoubtedly a severe issue before us.
Fortunately, as for the current riverbank conditions in the sections awaiting construction, apart from three places—from the northern end of the Mulongtan Dam to the northern end of the Mulongtan Bridge, from the left side of Dayongqiao Park to the right side of the northern end of the Lishui Bridge, and from Baotagang to the old Lusiwang ferry crossing—which are densely built-up areas of private houses, other sections either have reserved space for riverside avenues and embankment projects, or basically still present a relatively good natural ecological appearance, such as winding riverbank lines, wild protective forests, river bends, shallows, wetlands, grassy slopes, thickets, aquatic flora and fauna, and amphibians, and so on. These riverbanks that have not yet been channelized have reserved a relatively good material foundation for us to design embankment projects according to new concepts. The key to the problem now lies in the following:
First, update concepts.
Beginning in the 1970s, scientific and engineering circles in developed countries, in response to the negative impact of water conservancy projects on river ecosystems, raised the question of how to provide compensation. On this basis, theories and engineering practices for river ecological restoration emerged. River ecological engineering is called "river ecological natural engineering" in Germany, "multi-natural construction methods" in Japan, and "natural channel design technology" in the United States. Correspondingly, some developed countries have added content related to river ecological construction and landscape construction in the design and construction specifications for river regulation projects and embankment projects, or have issued special design guidelines for river ecology and landscape engineering.
Therefore, it is essential to draw on the latest domestic and international scientific research results, update concepts, loudly say "no" to concrete revetment methods that have only a single flood-control function and lack ecological and landscape functions, and, in accordance with local conditions, add diverse revetment forms such as earth, stone, wood, and vegetation, so as to simultaneously possess the three major functions of flood control, ecology, and landscape.
Flood-control function: Flood control is the premise and the primary foundational project. There is no disagreement on this point, so it is omitted here.
Ecological function: First, in the general principles for embankment planning and design, economic, technical, and ecological benefit assessments of the project should be carried out, changing the current single economic and technical assessment system; second, in view of the fact that the organic connection between the river and the ecological system on the banks has often been neglected in the past, embankment projects should be planned, designed, and constructed in a unified way according to the concept of a "river ecological corridor"; third, in view of the fact that the regularization and homogenization of river morphology will affect biodiversity to varying degrees, it is necessary to emphasize the diversification of river morphology in the layout of embankment lines and the selection of embankment types.
Landscape function: The landscape function is both implicit in the ecological function and an extension and sublimation of the ecological function. The Lishui Scenic Belt is being developed as Zhangjiajie's "Bund" and "Qinhuai River." Therefore, to make embankment projects also possess landscape functions, the core idea is to use modern ecological design concepts to create a natural, wild and interesting waterfront landscape environment. There are four basic principles: first, the principle of treating flood-control embankments as part of the river landscape; second, the principle of emphasizing the preservation of the river's natural aesthetic value; third, the principle of paying more attention to the construction of biological habitats; and fourth, the principle of satisfying the requirements of scenery, historical culture, and the ecological environment.
The successful experience of using earth embankments for revetment in Huangyan County, Zhejiang Province, an area with a high incidence of typhoons, is of great reference value: In 2002, the Yongning River channel in that county was undergoing river straightening and concrete revetment works. After the design team enumerated to the authorities the harms of river channelization and strongly argued the reasons for stopping construction, the authorities ultimately accepted the concepts of ecological and landscape design and used administrative means to "pause" the project. The design team transformed the already hardened flood-control embankment in three ways: retaining the original concrete flood-control embankment foundation and laying pebbles at the embankment toe; slowing the embankment slope, piling soil on the original vertical embankment slope, and converting it into planting beds; and restoring the entire embankment top road surface to an earth embankment and carrying out planting. For riverbanks that had not yet been channelized, according to the new flood-discharge capacity requirements, they retained sandbars and reed clusters on the riverbank as barriers against wind and waves, retained and restored wetlands in the waterfront zone, used earth entirely for the embankments, and adopted a series of synchronized measures to protect and restore natural processes and to protect and promote biological processes. It was completed and opened in May 2003, and in the summer of 2004 it withstood the most severe typhoon damage in 25 years and played an effective role in flood control and flood detention in the basin.
Long ago, the two banks of the Lishui River actually relied on a protective forest belt tens of meters to over a hundred meters wide for flood control and flood detention. Regarding the woods along the Lishui River, Qing dynasty "bamboo-branch lyrics" contain many descriptions, such as: "Across the stream a wine banner faintly beckons, ten li of official road reaches Waqiao. The whole road through pine woods is dim with mist, travelers pass unseen as horses neigh" ("Misty Trees of Waqiao"); "By the embankment thick shade protects the painted tower, on the dam flying catkins escort the departing boat" ("Spring Willows of Jinsha"); "Deep in the night songs enter the reed flowers, mountain shadows and pool mist trail in one stretch of green" ("Night Shoal Fishing Fires"), and so on. Even up to the 1950s and 1960s, the fire-willow groves on the Nanzhuangping riverbank were so thick that a single large tree required several people to encircle it, and its canopy covered three or four mu of land; when the pomelo groves on the Guanliping riverbank bloomed, their fragrance drifted straight across to the Nanmenkou area on the opposite bank. Unfortunately, these native species that had grown into a magnificent spectacle were destroyed all at once in the 1960s and 1970s during the Learn from Dazhai campaign of destroying forests to create farmland. In the Xixiping section on the right side of the southern end of the Lusiwang Bridge, part of the wild water-willow grove belt still survives on the riverbank, full of vitality and wild charm. Water willows have especially tenacious vitality and especially developed root systems. As long as, according to the new flood-discharge capacity requirements, earth embankments of sufficient height are filled and built on riverbanks suitable for earth embankments, and at the same time afforestation and other related measures are adopted, the flood-control function can absolutely be ensured. Moreover, earth embankments will also solve the ecological and landscape functions that concrete revetments find difficult to accomplish!