North moat

North moat

The north moat starts from the sanchahekou in the north of Xizhimen in Beijing, flows eastward through Deshengmen and Andingmen to the northeast corner, and connects with the East moat, with a width of 26 meters. In 1977, the reconstruction project was started. The upper section, from Sanchakou to Deshengmen, is 1877 meters long and is changed into an underground ditch; the lower section, from Deshengmen to the northeast corner of the city, is 4995 meters long and is a concrete straight wall type open river.

Location context

The north moat is a part of the north ring water system in Beijing. It starts from the exit of Xizhimen underground ditch in the West and ends at the northeast corner in the East, with a total length of 5.9 square kilometers, a landscape water surface of 14 hm2 and a green area of 15 hm2. The north moat is parallel to the North Second Ring Road, and is in turn Deshengmen, Gulou Street, Andingmen, Yonghe palace, Ditan Park and other important landmarks.

Governance status

Before the treatment, the north moat paid attention to the function of arch and drainage. It was a neat, straight and smooth river. The bank slope of the river, which used a lot of concrete or masonry, was "Sanguang River". There were only two types of cross-section. At the beginning of the river, 1.0KM was trapezoidal section, and the whole section was protected by precast concrete slab; the remaining 4.9km was rectangular section, and the river bottom was precast concrete Concrete retaining walls are built on both sides of the river. Its disadvantages are mainly manifested in the negative impact on the environment and ecology.

Hard retaining wall and bank slope use a layer of hard structure to isolate the contact between organisms and soil, destroy the overall balance of river ecosystem, make the river gradually lose its self purification ability, and aggravate the river pollution. Beijing has been dry for several years in succession, the water in the river can not be replenished and replaced in time, the hydrodynamic force is extremely poor, and the flow is not smooth, which has caused great damage to the river ecosystem. Therefore, the ecological restoration of the north moat is very necessary.

1. Design of double deck channel

The north moat uses the design of double-layer channel, that is, the upper layer is used as the landscape water surface, and the lower layer is used for drainage and buried with circulating pipes. Six hydrophilic trestles with different forms are set up in the Garden Road on both sides of the river, and two drop type biological filling steps are made in the river to create a water level drop, forming a waterfall landscape with a drop of 1.8m at the end of the section. It not only adds a beautiful scenic spot to the moat, but also realizes the flow of the river, making the river "live".

2. Ecological restoration technology of Zhiqiang River

(1) Removing the bottom protection of part of the river bed

The north moat has some difficulties in ecological restoration design. It is adjacent to Binhe Road in the north and the second ring road in the south, so its retaining wall is not demolished at one time. According to the characteristics that the river bottom and the retaining walls on both sides are concrete structures and "Sanguang river course", in addition to removing the concrete structure of the river bottom, permeable bricks are laid in the anti scour section of the sluice area to strengthen the exchange of water and soil at the river bottom.

(2) Retaining wall reinforced by planting trough

The north moat is located in the center of the city. Both sides of the moat are the main traffic roads in the city. The top of the upper part of the retaining wall of the river course is cut down to the normal water level, and there is no trace of concrete on the water surface. After removing the top, the retaining wall becomes shorter, which is conducive to the stability of the retaining wall. A new retaining wall with a thickness of 0.3m is built at the place 1.1m from the inner side of the retaining wall to the bank wall. The top elevation of the new retaining wall is also under the normal water level. Steel bars are planted at the bottom and partition walls are used at the top every 5m to connect with the original retaining wall. At the same time, a planting trough with a width of 0.8m is formed between the new retaining wall and the original bank wall. The filling material of the lower layer in the planting trough should be demolished as far as possible, and the waste should be used to minimize the external discarding; the layer should be filled with planting soil to meet the requirements of aquatic plant planting. After the reconstruction, the hard concrete can not be seen on the bank, which can cover up the characteristics of the embankment, relieve the visual pressure caused by the embankment with landscape, and form a green transition from the water surface to the bank slope.

3. Shallow bay

As far as possible, the bank slope part directly enters into the water, and the ecological brick and ecological bag revetment materials are meandering along the water side to form a shallow bay planting trough with variable shape and width, in which aquatic plants are planted to form a hierarchical bank slope greening.

4. Ecological bag revetment

Ecological bag revetment is a three-dimensional soft revetment based on engineering and ecological environment restoration. It is suitable for ecological restoration of stable soil or rock mass. Ecological lakeshore can promote the exchange of surface water and groundwater, and use its own function to purify water. This kind of revetment can not only stabilize the river bed, but also improve the ecology and beautify the environment, avoiding the negative effects of concrete structure.

5. Permeable pavement

Permeable brick, grass inlaid green stone slab, Tingbu stone and other permeable pavement methods are adopted in the river regulation. The permeable pavement has good permeability and permeability, can absorb water and heat, reduce the pressure of urban drainage and flood control, and is conducive to the utilization of rainwater and flood. The core technology of permeable pavement on impervious base is developed by reserving drain holes on impervious structure and using permeable pavement on surface. The permeable brick of aeolian sand is used for the first time in Beijing river regulation, and the new concept and technology of rainwater utilization are applied to every detail of river engineering.

6. River water quality maintenance

Under the condition of constant water level, submerged plants were planted at the bottom and slope of the river with a depth of 0.6-2.0m, and emergent plants were planted in the water land staggered planting troughs on both sides of the north moat. They directly absorb the nutrients such as N, P and trace elements in the water body to make it passivated, so that the water body develops to the reverse direction of eutrophication and the water body is purified.

While planting aquatic plants, proper amount of filter feeding fish and benthic animals such as snails and mussels should be raised under the condition that dissolved oxygen in the river can be guaranteed. The main function of filter feeding fish is to control the biomass of algae. Benthos can filter the suspended micro organisms and organic debris in the water and improve the transparency of the lake water. Through the water vivid, plant colonization technology, at the same time through the function of aquatic organisms to purify water, maintain water quality.

Today, the moat in the north is restoring its historical features, dredging the river, and widening the river. On both sides of the river, curved paths made of stones or green bricks are built. The paths are winding and charming, which is very romantic and poetic. Besides, corridors, pavilions, pavilions and pavilions with different styles are built beside the river, which is very pleasing and beautiful.

Open landscape

In September 2014, as a part of the second ring green road, the last section of the second ring green corridor in Xicheng District, beihucheng Hexi section, was basically completed and will be open to Beijing citizens on the 11th National Day. On the 3.3km greenway from Xizhimen bridge to Gulou bridge, there are three new scenic spots from east to west, namely, the sound of bells and drums, Desheng praying for snow and Tangxi Shengjing.

The sound of bells and drums

Located in Gulou bridge, the constructors use the existing waterfront Wharf in the limited space to renovate and reuse it. A waterfront platform has been added to the scenic spot, which is organically connected with the subway entrance square and wharf, and the planting area is interspersed in the middle, making it a waterfront landscape with a well arranged layout.

As the scenic spot is located in the Gulou subway station, the famous bell tower and Drum Tower on the central axis of Beijing are to the south, so the theme of the scenic spot is "bell and drum", which makes people feel the "aftersound of Bell and drum" of old Beijing that has played for 500 years.

Desheng prays for snow

"Desheng praying for snow" scenic spot is the key landscape node of the Hexi section of the north moat. According to reports, in 1757, when it was a severe drought, Qianlong came back from the city to offer sacrifices. When he came to Desheng Gate, he was glad to meet the heavy snow. Therefore, he wrote two snow praying poems in Desheng Gate, and established the imperial snow praying stele, which left the allusion of "Desheng praying for snow".

The construction of "Desheng praying for snow" scenic spot is centered on the arrow tower of Desheng Gate, focusing on the ancient and towering tower. In terms of landscape style, a large number of Pinus tabulaeformis, plum blossom and white peach trees are planted to set off the ancient city buildings and the theme of "praying for snow", and cultural elements such as the disappeared "imperial stele Pavilion", the legend of Deshengmen and old photos are integrated into the landscape to become the carrier of displaying the traditional culture of Deshengmen.

Tangxi Shengjing

Located in the northwest corner of Jishuitan bridge. Jishuitan is a huge lake built in Yuan Dynasty after Tonghui river flowed into the city. It was called "Xiya" before Ming Dynasty and Qing Dynasty. Based on the extemporaneous poem of Jishuitan in the 26th year of the Qianlong reign of the Qing Dynasty, the scenic spot of "beautiful scenery in the west of the pool" has added a river crossing plank road to connect the north and south banks on the basis of the existing greening. Taking the natural waterscape as the core, it has built many scenic spots around it, such as qinlanxuan, hefengwu, fuyanfang, qinfangting, yingyuzhou, etc., forming an ancient Chinese garden landscape, which can be enjoyed during the roaming To a corner of the pool in those days.

Address: Yangzhou

Longitude: 119.42838191986

Latitude: 32.400798592426

Chinese PinYin : Bei Hu Cheng He