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Msimbazi River Water Level and Conductivity Monitoring System

Solution Overview

A water level monitoring system was installed underneath Selander Bridge at the outfall of the Msimbazi River to measure water levels and conductivity for at least one month as part of comprehensive flood modeling efforts.[2] This monitoring infrastructure formed a critical component of an integrated survey campaign that included bathymetric surveys, RTK-GNSS surveys, UAV LiDAR, and UAV Photogrammetry designed to support flood modeling purposes.[1] The implementation addressed severe flooding challenges in the Msimbazi Basin, where an estimated 27 percent of Dar es Salaam's population resides in what has historically been a fertile floodplain and the city's main water source.[5]

Technical Components

The water level logger installed beneath Selander Bridge was designed to measure both water levels and conductivity (salinity) parameters continuously.[2] Vertical referencing of the installed equipment was considered very important to link the measured levels to the terrain heights, ensuring accurate integration with topographic data.[2] The monitoring system was complemented by two water level gauges deployed across the Msimbazi Basin that provided data at 15-minute temporal resolution during 2018.[3] The broader survey campaign utilized an integrated approach combining bathymetric and topographic surveying of flood-prone rivers with advanced remote sensing technologies.[1] Field data collection was conducted by a team of six people, including four mappers and two technicians, equipped with Android smartphones running Open Data Kit (ODK) software.[5] A hydrological data collection protocol for ODK was developed in collaboration with Deltares, with the first field survey carried out alongside Deltares associates Bobby Russell and Hessel Winsemius, both experienced in hydrological surveys.[5] TU Delft student Kirsten van Dongen co-developed a method to use low-cost hardware that demonstrated similar accuracy and precision as professional-grade survey equipment.[5]

Implementation Details

The entire survey campaign, including the water level logger installation, took place from February 14th until February 20th, 2019, with only the retrieval of the water level logger completed after this period.[2] The survey of river cross-sections and hydraulic structures along the Msimbazi River supported the creation of a comprehensive hydraulic model of the area that led to the development of a more realistic flood hazard map of the most vulnerable areas.[5] The resulting maps were used to create detailed flood models for the city that are being used to inform a multi-billion dollar investment in drainage infrastructure.[4] The project was designed to be complementary to the ongoing Tanzania Urban Resilience Program (TURP), implemented by the World Bank.[5] The product of this assignment was the development of a wider flood model that would assist in providing the evidentiary basis for investments in the basin.[5] The water level gauge data collected in the Msimbazi Basin had a short period of record covering only 2018, representing a limitation in the temporal extent of available monitoring data.[3]

Benefits and Impacts

The comprehensive hydraulic model developed from the survey data led to the creation of more realistic flood hazard maps identifying the most vulnerable areas in the Msimbazi Basin.[5] These detailed flood models are being used to inform a multi-billion dollar investment in drainage infrastructure for the city.[4] The wider flood model developed through this assignment assists in providing the evidentiary basis for investments in the basin, supporting strategic decision-making for flood risk reduction.[5] The low-cost hardware methodology co-developed with TU Delft demonstrated that it could deliver similar accuracy and precision as professional-grade survey equipment, potentially enabling more cost-effective monitoring approaches.[5]

Climate Adaptation Relevance

The monitoring system directly addresses severe flooding challenges that have become increasingly critical in the Msimbazi Basin, where major flood events were experienced in seven out of the last ten years.[6] In 2019 alone, nine major flood events took place in the middle and lower part of the Msimbazi Basin, with flooding occurring at least twice a year during every rainy season.[6] Each year, Msimbazi flooding leads to fatalities and destroys critical infrastructure, while urbanization pressures and encroachment have destabilized river banks, increased erosion, and put approximately 50,000 people from the most vulnerable communities in the path of floodwaters.[5][6]

Business Analysis

The flood modeling outputs from this monitoring initiative are being used to inform a multi-billion dollar investment in drainage infrastructure, demonstrating significant financial mobilization potential.[4] The project was structured to complement the ongoing Tanzania Urban Resilience Program (TURP), implemented by the World Bank, indicating integration with established international development financing mechanisms.[5] The development of a wider flood model assists in providing the evidentiary basis for investments in the basin, serving as a critical tool for justifying and directing capital allocation for flood risk reduction measures.[5] The demonstration that low-cost hardware could deliver similar accuracy and precision as professional-grade survey equipment suggests potential for cost-effective scaling of monitoring infrastructure in resource-constrained environments.[5]

Sources