Throughout sub-Saharan Africa, agricultural activities in urban and peri-urban areas are threatened by urban sprawl. These activities are important not just for the livelihoods of those who take part in it, but also for the food security of the city. Historically, in Kumasi 40% of the crops in the city are sourced from urban and peri-urban agriculture. However, Kumasi is also a city that is growing rapidly both in population and in area: since the 1980’s population has more than quadrupled and the area has increased more than tenfold. Because of this, there is a need to find ways to maintain urban and peri-urban agriculture under the threat of urban sprawl and the climate change in the future and also work well in the Kumasi context.
We used the agro-hydrological model AquaCrop informed by 4.5 years of local weather data, soil data and crop data to model the effectiveness of adaptations in maintaining food security for three neighbourhoods in Kumasi. Local farmer management practices that were determined by a survey of 150 Kumasi farmers made a distinction in management practices between adaptations and crops. This model gave yields and irrigation water uses for five crop groups that are commonly cited as crucial for food security. Combined with population growth predictions and land use and land cover analysis this allowed us to make a statement about how well adaptations can meet current and future demand of crops and how much space is needed to meet demand. This model was supplemented with a survey of vendors and farmers to investigate barriers against- and preferences for adaptations.
Backyard gardening and sack gardening turned out to be the best options to maintain peri-urban agriculture. These adaptations use the least space, for the highest yields. From the survey of farmers and vendors, no strong objections were found against the implementation of these adaptations. Over 80% of surveyed farmers and vendors felt that backyard gardening was a good adaptation to maintain peri-urban agriculture in Kumasi. Backyard gardening and sack gardening are optimally suited for growing vegetables and legumes, which are the easily perishable crops and thus benefit from a short supply line, which many vendors cite as solutions for spoilage.
It is possible to ensure self-sufficiency for these crops with 5-9% of total land in the Feyiase neighbourhood, 11-20% in Ejisu and with 14-22% in the Kwadaso neighbourhood. It is therefore recommended to target at least a majority self sufficiency, by reserving a >50% fraction of this land for backyards and sack gardening spaces. At the same time, any available marginal lands should be allocated for the growth of cereals and tubers, to allow for the production of these subsistence crops, until the production of the remaining demand is fully met by rural import. With these adaptations and recommendations, it is possible for peri-urban agriculture in Kumasi to maintain its important role throughout the coming decades.
In order to determine if there are any deviations from these conclusions, future research should focus on including empirical crop data tailored to AquaCrop or use a model that is better suited to represent the chaotic nature of (peri-) urban agriculture. While the model results do not differ significantly from the crop yields as found in literature, a model informed by local crop data can be an even better representation of the situation in Kumasi. Furthermore, a study into the long-term effects of adaptation on nutrition can reinforce our conclusions on food security.
Finally, there is an opportunity to develop more high-tech agricultural methods like greenhouses and aquaponics. There is also an opportunity to incorporate wastewater reuse schemes, following examples from other countries, such a urine reuse, or low-tech treatment with sludge harvest. For this, it is recommended to set up educational programs and pilots.

To develop warning systems for flood events, create precipitation-runoff relationships, validate runoff models, or to understand the behaviour of rivers, understanding of the amount of water flowing through rivers is needed. The low-cost and novel gauging method using Large-Scale Particle Image Velocimetry (LSPIV) could complement discharge measurements at locations and stages where the possibilities of using traditional gauging methods are limited. This report investigates the feasibility of using LSPIV to quantify river discharges in an equatorial urban stream with fast response time.

LSPIV uses videos to extract surface flow velocities by tracing movements of seeds on the water's surface. Combined with the local bathymetry and water level, an estimation of the river's discharge can be made. This study consists of two sets of experiments. The first set of experiments were performed at the Dommel regarding processing software, image preparation, seeding densities, and point of views and discussed by assessing their accuracy relative to benchmark measurements -- using the mean error and root mean squared error -- and the method's precision – using the relative standard deviation.

The second set of experiments were performed along the Chuo Kikuu, Dar es Salaam, Tanzania. A flood wave was monitored through the capture of 73 5 second videos. These videos were turned into separate frames and corrected for lens distortion and perspective distortion. Thereafter the frames were gray scaled and gamma correction was applied. After the LSPIV process additional filtering removed unrealistic low flow velocities, and through substitution missing velocities were replaced with flow velocities based on the vertical logarithmic progression relationship between the surface flow velocities and water depth. The surface flow velocities found using this method match optical observations. Discharges were estimated using the empirical depth-average coefficient and local bathymetry. Results showed that the post-processing reduces the uncertainty bandwidth with 37% and increases the mean flow velocities with 96%.

The found discharges were compared with precipitation measurements observed at a nearby TAHMO meteorological station. The total volumetric precipitation was determined by estimating the contributing catchment using a digital elevation map and the locations of man-made drainage systems. When comparing the volumetric precipitation with the flood wave, a runoff coefficient of 53% [35-68] is found. This coefficient falls within the ranges found in literature, but is probably an underestimation of the true runoff due to an overestimation of the catchment area and underestimation of the discharges.

This study shows that the LSPIV method is feasible for continuously monitoring flood waves in an urban environment. Especially during peak flows LSPIV proves to be valuable, as observations using conventional gauging methods are labour intensive, unsafe, or not executable. Because of the possibility to monitor streams from a distance -- which ensures access to power and safety against vandalism -- there is a possibility to observe complete flood waves at regular intervals without the need for direct contact with the water. For Dar es Salaam, this method opens doors for continuous and secure stream monitoring, at low costs and with local devices.