Sedimentation process in Inwa waterway, Mandalay
By Kyi Kyi Lwin
River transport system save cost and energy has little environmental impact compared to other modes of transport. Navigation enhancement is crucial for the development of national economic.
The location of the study area is Inwa waterway which length is 8.536 km (5.3 miles) at Mandalay in middle of Ayeyarwady River. Inwa waterway is one of the constraints in Mandalay waterway, which is one of the most important inland waterways for the transportation.
The sedimentation caused by gold mining, deforestation, climate change and some infrastructure structures such as hydropower station and bridge, which are the vital problem in Ayeyarwady River. The high sediment load and resulting river bed rises compromise navigation on the river.
For example, in 2008, the new bridge (Yadanabon Bridge) was constructed across Ayeyarwaddy River. Due to the new bridge construction, the amount of sedimentation is rapidly increasing. As a result, the vessels that are passing along river have faced the shoaling problem, causing a series of sand bars appeared in river. Moreover there are social impacts; for example, the people who stayed near river had to move other places, due to the construction of bridge. After 1983, the sand bars appeared in front of the Sagaing port every year.
The sedimentation problem is very challenging for the Directorate of Water Resources and Improvement of River Systems (DWIR, Mandalay) to maintain sufficient water depth for navigation in the area, especially in the dry season. With dredging, they try to achieve a minimum water depth of 3m (below the Mean Low Water Level) along the downstream of Inwa Bridge.
Survey for Field Trip
To get a better understanding and investigate the activities of rivers on the sedimentation and the sediment impact on navigation, I went to the Inwa water way together with my students from Myanmar Maritime University and staff from DWIR.
Director U Win Hlaing explained about the problem of water way and historical data of it. Snag rocks occur on both side of Sagaing and Amarapura bank. DWIR operated the dredging work and removed snag rocks to improve the waterway during dry season of 2013-2014. However, excavated sand bars reappear again and lead the shoaling problems. Director U Win Hlaing said “the problems at waterway are navigation difficulty, shoaling problem and recently sandbars appeared. The construction of new bridge (Yadanabon Bridge) is also a threat to the flow regime of the river, and along Inwa waterway, it is necessary to improve navigational channel.” Hence, the picture indicates the improvement area for dredging of sand deposits by backhoe dredger near bridge.
During an interview, Ma Ei who lived near the new bridge said, ” due to the construction of the new bridge, the sandbars are appeared and the transportation are difficult for vessels.”
Moreover, their houses were moved to new places and also they cannot perform their daily works on cargo carrying, because any vessel could not pass to the river due to the shallow water depth, especially in the dry season. The houses cannot get the good quality of water.
Another interviewer, Ma lei told me that around the dredging area she is doing good business and that her family is happy for getting new friends and more income. She also explained me that developers and investors came to buy dredged sand for construction materials.
To get better transport along waterway, it is necessary to improve the navigational channel. It can provide river training works to counter the migrating sand bar which are an integrated part of the improvement of navigation on the Ayeyarwady River besides dredging maintenance.