This thesis contributes to the scientific underpinning of the battle against fruit frost. Fruit frost is the freezing damage to blossoms when in the growing season the night temperature drops below 0±C. This results in damaged or undeveloped fruits, and a yield loss for the fruit farmer. Several techniques against fruit frost have been developed, including sprinkling and wind machines, often in combination with meteorological models, for example, to predict air temperature. However, the contribution of heat exchange with the soil to moderate orchard temperatures is often not included. In this thesis, this heat transfer is investigated, as an increase of heat transfer from the soil to the orchard during the night is a potential remedy against fruit frost. The research is based on measurements for soil temperature, soil heat flux, and soil moisture from two locations (1. Haarweg (Gelderland), The Netherlands 2. Bushland (Texas), The U.S.A.). First, a numerical model is developed to calculate the temperature and soil heat flux profiles for a soil layer. The results are compared to the results of an already developed analytical model. Second, the thermal parameters, that are of influence on the heat transfer, are analyzed by assessing a) their robustness in relation to the model and b) their relation to soil moisture. Because a numerical model is more flexible for shorter periods of data compared to an analytical model (because of underlying assumptions), it can be used to relate the parameters to (daily) varying soil moisture. Third, the numerical model for heat transfer is extended to the vegetation layer, and, again, the results are compared to analytical results. The model is created by assuming homogeneity in both separate layers and by discretizing the governing heat equation over the domain. The results show that the model reproduces temperature and soil heat flux in the soil layer with similar accuracy as the analytical, harmonic model. One thermal parameter, the diffusivity, is robust and does not show a clear dependency on soil moisture. The model is however sensitive to deviations in the other parameter, the heat conductivity. The model shows a clear relation between conductivity and soil moisture, and from this, a site-specific quantitative relation is determined. This relation however is only valid in the investigated region of moisture variation and we recommend future research to cover data in a broader range of soil moisture. Overall, we conclude that the model successfully reproduced the temperature and soil heat flux throughout the full vegetation-soil continuum.

The city of Guayaquil suffers from regular floods. During the wet season, typically from late December until late April or early May, multiple floods per week can occur. Mainly the excessive rainfall in combination with high tide penetrating into the city results in a high flood risk, but some flood-prone areas can also flood in case of spring tide only. The main objective of this research is to investigate the possibility of reducing pluvial and coastal flooding in urban areas by constructing a (semi-permanent) barrier in a sea branch, which retains the incoming tide and creates storage for excessive rainfall. In addition, local storage areas spread over the city are considered to delay stormwater runoff into the sea branches. Based on a system analysis and by numerical modelling, several closure locations and their effects are assessed. Temporary storage of stormwater behind a barrier in a sea branch is a suitable solution to prevent both coastal and pluvial flooding. Based on the results of this research and possible locations of the barriers, a combination of three selected barriers is most opportune, because all catchment areas adjacent to a sea branch can drain their stormwater in a closed-off part behind one of these barriers. In order for these barriers to be effective, they must be closed during low tide prior to heavy rainfall. All three barriers are able to withhold the stormwater volume from their corresponding catchment areas during a 10-year design rainfall event. Even in the event of the highest possible water level during low tide, being neap tide in combination with the storm surge of El Niño, the storage capacities are sufficiently large. Besides the large-scale and small-scale solutions that are currently considered by the local authorities, they are advised to also consider the intermediate-scale solution presented in this study. Local stormwater storage in the form of water squares in parks and playgrounds is a small-scale solution to reduce pluvial flooding. The storage capacity of these areas is much smaller than the storage capacity behind a barrier, but it is a solution for low-lying urban areas that are not adjacent to a sea branch or river. When the storage capacity of parks and playgrounds in some catchment areas is not sufficient, underground storage basins can also be considered as local storage areas. The local authorities are advised to set up regulations on return periods for designing flood risk-reducing structures and to assess the economic losses of floods in urban areas, in order to be able to estimate the acceptable cost of these structures.

Flooding is a very costly natural disaster especially when it hits urban areas. Yet synthetic aperture radar (SAR) based flood mapping barely works in urban areas. Buildings and man made objects have similar backscatter signatures as still standing water. This makes them hard to distinguish from one another. Structures can block the visibility of the ground surface for side looking SAR satellites making large parts of potentially flooded ground going unseen by SAR satellites. Smooth surfaces and limited ground visibility make it hard to produce accurate flood maps using SAR in urban environments. Here we have shown how the use of a temporal stack can improve the result of urban flood detection with SAR. Traditionally SAR based flood mapping uses a single image or an image pair to classify flooded and non-flooded pixels. This study found these methods unable to detect flooded pixels in an urban setting. By using a temporal stack of SAR images more pixels are correctly classified as flooded while keeping false positive classifications low. However the number off correctly classified pixels remains too low to be useful on its own, by adding ancillary data in the form of a high resolution DEM an accurate flood map for a very specific area is produced. This means that SAR images are not suitable for flood mapping in urban areas as a single source of information. When they are combined with other data they have the potential to produce accurate flood maps useful for First responders when the next flooding disaster hits.