KENYA: Monitoring water levels to reduce flood risk
A water radar sensor that measures the level of water
Nairobi, 18 June 2010 (IRIN) - Kenyan authorities have installed water radar sensors to monitor levels on the western Nzoia river in an effort to mitigate flood damage, officials said.
The river perennially bursts its banks, flooding parts of Budalangi region in Bunyala District, with devastating results for thousands of people living in the area.
"The sensors are installed at a bridge, and have a GPRS [general packet radio service] modem that is solar-powered," Daniel Maina, the flood management coordinator with the Western Kenya Flood Mitigation Project, told IRIN. "Just the way you send a text message, you just call the modem like a phone, and get feedback on water levels."
The water radar sensors have been installed in the three locations of Webuye, Rwabwa and Sigomre areas in the Nzoia River Basin. They provide alerts about water levels in real-time, helping in disaster preparedness.
The eye, underneath the radar sensor, records the water level. When dialed, the modems, which are fitted with subscriber identity module cards, relay data in the form of graphs to the flood management centre and the Kenya Meteorological Department.
Rwabwa station is about 30km downstream of Sigomre. According to Maina, the water takes about eight hours to reach Rwabwa from Sigomre. Data from Sigomre helps in the prediction of expected water level crests at Rwabwa.
Several Hydromet Stations in the Basin record rainfall levels. Rainfall forecast data from the meteorological department is integrated with water level data to produce models that are circulated to key stakeholders, including government and UN agencies.
Initial flood watch bulletins are sent to the Bunyala District Commissioner (DC), who passes the information to the community through a radio with a 25km broadcasting radius. Content is read in the local Kinyala language. For example, if there is a broken dyke, the DC goes on radio to mobilize support to repair it.
Besides water and rainfall monitoring, afforestation and construction of small dams is going on upstream to reduce water speed and siltation. The upper catchment regions include Mt Elgon, Cherangani hills, Burnt Forest and the Kakamega Forest.
"In the upper catchment area, the main problem is soil erosion; in Budalangi, the flooding is due to siltation, which leads to higher water levels," Maina added. "This is especially the case at the river mouth, which prevents water easily evacuating into [Lake Victoria], leading to a back flow of flood waters," Main said. River mouth dredging is also ongoing as part of the eight-year, World Bank-funded project.
Nzoia's course meanders dangerously close to the dykes and population settlements in some parts of Budalangi. The dykes at Budalangi were constructed between 1977 and 1984 and were meant to last 20 years. A multi-purpose dam is being designed to further protect Budalangi, which experienced massive flooding in 2007.
Despite the benefits, the project has been affected by vandalism of solar panels at the water radar sensors, high telecommunication network charges and weak signal strength.