Flooding Risk Assessment in Jinan, China

In this project, I will examine and evaluate the exposure and vulnerability of different urban communities in Jinan city to possible flood hazards through empirical analysis and spatial analysis.

Firstly, I will introduce how people in Jinan have interacted with water over time. Then, I will analyze the concentrated precipitation and limited flooding capacity as driving factors of the flooding pattern in Jinan City.

With the empirical analysis, I will explore the local spatial patterns of the regions that are exposed to flooding hazards. In this process, I will identify two key communities that are more vulnerable to flooding disasters and analyze how the infrastructures, people, and other properties of the community limit the ability of the local residents to handle the flood disasters.

With data visualized in maps and charts, this project can be a good reference for the city council to improve their water management systems and preventive measures.

Jinan is a city located in Eastern China, with 5 million people. It is the capital of Shandong province, and famous for its natural springs.

Since ancient times, Jinan has had a rich history. If you are traveling to Jinan, you might find many traces of this history being told in many parts of the city.

Since

Jinan is an ancient city, it has seen many changes over time. The rapid expansion of urban areas between the 1980s and 2020 resulted in many kinds of urban landscapes within the city.

"Springs are out, drain as streams and rivers in the city, and meet at Daming Lake." This romantic description frames where the water comes from, and where the water goes.

In the past, people drank this water and boiled tea and soup with the water. The water is clean and rich in beneficial minerals. Both the poets in the Tang dynasty and Song dynasty left poems appreciating the tastes of the natural spring water.

People used this water to wash clothes and vegetables. If you could have visited Jinan in the 20th century, you would have definitely seen the ladies by the streams washing their clothes by hand.

People also used this water to commute. In the Qing dynasty, many different boats were gathered on the river, transporting and trading salts and other products.

Lastly, people used this water to irrigate and produce goods. In the 20th century, many industries exploited a large amount of water for various purposes, including producing papers, coins, commodities, and machines.

People have benefited from the springs and waters, but....

"Good fortune follows upon disaster； Disaster lurks within good fortune." --- Tao Te Ching

People Suffer from both droughts and floods ...

The natural springs in Jinan have dried up before. Records show the Baotu Spring dried up in 1073 AD and 1640 AD. The most recent one was between 1999 and 2001.

The climate was hot and dry during spring and fall, along with massive agricultural water consumption and over-exploitation of groundwater by industries in the 20th century. These factors combined and led to a rapid decline in the groundwater level in Jinan. When the Baotu Spring Water level dropped to 27.01 meters, the springs stopped flowing out of the ground.

“At 5:00 p.m., my mother drenched to the skin, pushed her bicycle all the way from Qinglong Bridge, and returned home in the water. She was swept down by the current on the way home, but fortunately, people passing by pulled my mom up from the water.” --A witness of 2007 Jinan Flood

The 2007 Jinan Extraordinary Rainstorm was a very heavy rainstorm that hit the city of Jinan on the evening of July 18, 2007, from 5:00 pm to 8:00 pm (UTC+8). During these three hours, a rainfall of 180mm (7 inches) accumulated.

The heavy rainstorm continued for more than three hours, and the Ginza underground supermarket in central Jinan was quickly filled with rainwater.

On July 21, the Civil Affairs Department of Shandong Province issued a notice saying that, by the verification of statistics of the districts and counties in Jinan, as of July 21, the rainstorm disaster in Jinan led to a total of 34 deaths, 4 people missing, 171 people injured. After investigation, the causes of death were mainly drowning, short-circuiting of electric wires or death by lightning, and death by building collapse. In addition to these, there were also some victims who were trapped in their cars when the heavy rain occurred and eventually died.

Because of the great impact caused by this incident, the relevant departments of Jinan City began to analyze this extraordinarily heavy rainfall flood disaster.

It was finally determined that the main causes of this disaster were the extraordinary intensity of precipitation, the special underground environment, the limited flooding capacity, and the specific time period of occurrence.

Jinan has a subtropical climate. During summer, the weather is typically hot and humid. The warm and wet monsoons bring a lot of precipitation into the city, in the form of thunderstorms. During the water, the weather is typically dry and cold.

Besides the meteorological data above, According to Chang et al (2018)'s study, the heaviest summer precipitation typically occurs in the Southern mountainous region of Jinan, as the main factor of the city's flooding disasters, and the overall precipitation is still increasing.

Jinan has a long history of water management. Because Daming Lake is located in the Northern part of the ancient city, there were only three gates in ancient Jinan city.

During Northern Song Dynasty, in order to better drain the water out of the lake during the flooding time, local governor Zeng Gong built the North Gate for only water but not land transportation.

Also, the complex network of streams and rivers originating from springs in the city was also good at draining flooding water out of the city, so there was not a significant number of documented floods in the history of Jinan.

However, the industry was introduced in Jinan during the 20th century, the pavement roads gradually covered the streams and minor rivers, and the urban area has extended greatly.

The changes in the land cover have been influential to the city's water cycle. The impermeable surfaces block the water from infiltrating downward, so the rainfall accumulates and forms the surface runoff, which can be regarded as a flooding disaster if the precipitation is heavy.

On the other side, the impermeable surface and the underground impermeable structures also block the underground water from flowing out of the surface. Many streams and rivers disappear, so the draining capacity is greatly decreased compared to ancient times.

“When it rains heavily in summer, I can relax at home and enjoy a ‘sea view’, and I think it is really 'worth' buying this house.” -- A resident in Jinan

In 2015, the Chinese government initiated the "Sponge City campaign" starting in 16 cities, including Jinan. This initiative aims to restore the hydrological system in the urban area, including changing permeable surfaces to increase infiltration and developing more ways to drain stormwater and store rainfall for dry seasons.

Jinan city government planned to improve the water management system and target over 40% of the urban surface to meet the goal of the "Sponge City" initiative. However, it is unclear how effective the "Sponge City campaign" will be against flooding hazards in the future.

In conclusion, there are various factors limiting the capacity and making Jinan City be vulnerable facing the possible flooding hazards.

1. The rapid urban expansion and change in land cover have resulted in massive impermeable surfaces.
2. The mismanagement of natural springs has decreased the capacity of draining water.
3. The uneven terrain increases the pressure of water management in lowland areas.
4. The flawed design of pipeline systems and roads makes some parts more vulnerable to floods.
5. The lack of pump stations makes some regions of the city harder to drain water out.

Currently, there are few studies done about the flooding risk assessments of Jinan City in English. However, there is a lot of research on other Chinese cities. For example, in an article about Guangzhou’s flooding risk, the authors utilized spatial interpolation and spatial regression models to analyze the sensitive areas of all metro lines in Guangzhou. My numerical analysis will bring similar methodologies to the case study of Jinan.

I access and download the digital elevation data, administrative boundary data, and water bodies of Jinan from Copernicus and Openstreetmap. Also, I will make a table of the river monitor stations around the city, with their warning water levels.

With the result, in the following part of the Storymap, I will examine two neighboring but different communities (a.k.a. Microdistricts/Apartment Complexes) with their risks and preparedness for possible flooding disasters. Please note that these two communities both have moderate risks to the possible river flooding.

Just like many old communities built in the 1980s-1990s, the apartment buildings of Zhijinshi community usually have six levels, several entrances per building, and several units per level per entrance.

We usually called these buildings  Khrushchyovka , a style that the Chinese borrowed from the Soviets. This kind of buildings has effectively fulfilled the housing demands, lowered the costs of construction, and preserved the privacies of the residents.

The drawbacks, in general, are a lack of barrier-free facilities, a lack of public spaces, and a lack of living spaces.

This neighborhood is relatively old. The infrastructures, including the building materials, water pipelines, electrical cables, and streets are all exposed to different risks under the scenario of flooding disasters.

Not only the Zhijinshi community, all the communities built in China during the 1980s and 1990s have similar issues when facing the flooding disasters:

Juxian Community, including North Apartment Complex and South Apartment Complex, were built in 2012. Inheriting the former design of  Khrushchyovka , the buildings are designed higher (18 levels), with both elevators and staircases, and of course, more units per building.

With over 2000 families living in this area, Juxian Community is one of the most densely populated communities in Jinan City. Although it is newly built, there are still some issues in this community, as well as other newly-built communities in China, when facing flooding disasters:

By analyzing both old and new communities in Jinan city, we have identified some key weaknesses for both of these communities, which increase the vulnerability of these communities to flooding disasters.

In Jinan, a city with a 5 million population, how to manage the possible flooding disaster has been treated as an important city agenda.

Jinan is sensitive to flooding. Each year, the monsoon brings a lot of precipitation during the summer, particularly in the form of thunderstorms. In 2007, an Extraordinary Rainstorm attacked this city, marking one of the most devastating natural hazards in Jinan.

On a general scale, Jinan is not well-prepared for flooding. Many factors attribute to its vulnerability against flooding, including but not limited to the impermeable urban surfaces, the mismanagement of natural springs, the uneven terrain, the flawed pipeline systems, and the lack of pump stations.

On a local scale, different communities are exposed differently to the flooding hazard, and both old and new communities have some flaws, whether inherited or improvable, to the flooding hazard. We are aware of these problems, but it is true that these problems are not easy to be solved.

With analyses, maps, and charts, I hope this project can be a good reference not only for city residents but also for the general public to learn more about the flooding risks in Chinese cities.

Chang, Xu, Z., Zhao, G., Cheng, T., & Song, S. (2018). Spatial and temporal variations of precipitation during 1979–2015 in Jinan City, China. Journal of Water and Climate Change, 9(3), 540–554. https://doi.org/10.2166/wcc.2017.029

Cherqui, F., Belmeziti, A., Granger, D., Sourdril, A., & Le Gauffre, P. (2015). Assessing urban potential flooding risk and identifying effective risk-reduction measures. The Science of the Total Environment, 514, 418–425. https://doi.org/10.1016/j.scitotenv.2015.02.027

Cheng, T., Xu, Z., Hong, S., & Song, S. (2017). Flood Risk Zoning by Using 2D Hydrodynamic Modeling: A Case Study in Jinan City. Mathematical Problems in Engineering, 2017, 1–8. https://doi.org/10.1155/2017/5659197

Cui, B., Wang, C., Tao, W., & You, Z. (2009). River channel network design for drought and flood control: A case study of Xiaoqinghe River basin, Jinan City, China. Journal of Environmental Management, 90(11), 3675–3686. https://doi.org/10.1016/j.jenvman.2009.07.010Jinan Hydrological Bureau. (2019). Hydrological Information Monthly Report of Jinan City. http://www.jnsww.com.cn:36789/ms-mcms/upload/1/editor/1557039568598.pdf

Fenghuang News. (2017). Please Save, The authoritative map of Jinan's water-prone roads is here. Last Retrieved in December 2021. http://sd.ifeng.com/a/20170725/5851829_0.shtml

Fenghuang News. (2015). Congenital deficiencies, acquired disorders. Jinan Zhijinshi and Sankongqiao area flood every time it rains. Last Retrieved in December 2021. http://sd.ifeng.com/news/fengguanqilu/detail_2015_08/17/4240613_0.shtml

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Lin, W., Sun, Y., Nijhuis, S., & Wang, Z. (2020). Scenario-based flood risk assessment for urbanizing deltas using future land-use simulation (FLUS): Guangzhou Metropolitan Area as a case study. The Science of the Total Environment, 739, 139899–139899. https://doi.org/10.1016/j.scitotenv.2020.139899

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Netease News. (2021). Review of the 2007 Jinan heavy rainfall disaster, the moat backed up, 34 people were killed and about 330,000 people were affected. Last Retrieved in December 2021. https://3g.163.com/dy/article/GD18JUBP0534PAAE.html

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The Paper News (Pengpai News). A section of Jinan will become a "sea" when it rains! A citizen: living in a "sea view room". Last Retrieved in December 2021. https://www.thepaper.cn/newsDetail_forward_8916265

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