Nassir S. Al-Amri

Flash flood hazard mapping based on quantitative hydrology, geomorphology and GIS techniques (case study of Wadi Al Lith, Saudi Arabia)

Flash floods are considered as catastrophic phenomena possessing major hazardous threat to the coastal cities, towns, villages and infrastructures. This study deals with the evaluation of flash flood hazard in the ungauged Wadi Al Lith basin depending on detailed morphometric characteristics of Al Lith basin and its sub-basins. For the detailed study, ASTER data were used for preparing digital elevation model (DEM), and geographical information system (GIS) was used in the evaluation of linear, areal and relief aspects of morphometric parameters. The major parameters such as watershed boundary, flow accumulation, flow direction, flow length and stream ordering are prepared using the ArcHydro Tool. Surface Tool in ArcGIS-10 software, and ASTER (DEM) was used to create different thematic maps such as DEM, contour, slope aspect and hill shade maps. Twenty-five morphometric parameters were measured, calculated and interlinked to produce nine effective parameters for evaluation of the flash flood hazard degree of the study area. Based on nine morphometric parameters which affect the hydrologic behaviour of the Wadi, by influence on time of concentration which has a direct influence on flooding prone area. The flash flood hazard of the Al Lith basin and its sub-basins was identified and classified into three groups (high, medium and low hazard degree). The study provides details on the flash flood-prone area (Wadi Al Lith) and the mitigation measures. This study also helps to plan rainwater harvesting and watershed management in the flash flood alert zones.

Geostatistical analysis using GIS for mapping groundwater quality: case study in the recharge area of Wadi Usfan, western Saudi Arabia

The scarcity of water is one of the main issues in Saudi Arabia. In particular, the extreme climate in the form of less frequent rainfall affects the groundwater availability. Moreover, groundwater has been depleted by the increase in population. In this research, the spatial distribution of groundwater quality has been developed, and the prediction of groundwater chemical parameters has been made using geostatistical analysis in geographic information system (GIS) software. The study area is Madrakah village as the recharge area of Wadi Usfan located in the western region of Saudi Arabia. Ordinary kriging method was applied to map the spatial distribution of the groundwater chemistry. Most of the groundwater is not suitable for drinking purposes. Groundwater chemical parameters are decreasing toward the eastern part of Madrakah village. In predicting groundwater chemistry distribution maps, data transformation has been executed to reduce the skewness on most of the chemical parameters. The best semivariogram model for every parameter varies based on the root mean square error (RMSE) criterion. The groundwater chemical parameters, i.e., Na+, Mg2+, Cl−, conductivity, salinity, and total dissolved solid (TDS), have a strong spatial dependence, while, NO3− and temperature have a moderate and weak spatial dependence, respectively.

Development of storm hyetographs for flood forecasting in the Kingdom of Saudi Arabia

This paper presents the derivation of the design storm hyetograph patterns for the Kingdom of Saudi Arabia based on real rainfall events from meteorological stations distributed throughout the Kingdom. Two thousand twenty-seven rainfall storms for a 20–28-year period were collected and analyzed covering 13 regions of the Kingdom. Four distinct dimensionless rainfall hyetograph patterns have been obtained over the Kingdom, while two patterns have been obtained for each individual region because of the lack of data for long-duration storms in individual regions. The resulting dimensionless rainfall patterns for each region can be used to develop storm hyetographs for any design duration, total rainfall depth and return period. It has been shown that the developed storm hyetographs have different features from other storm patterns that are commonly used in arid zones. The study recommends using these curves for the design of hydraulic structures in Kingdom of Saudi Arabia and regions alike.

Development of intensity–duration–frequency curves for the Kingdom of Saudi Arabia

ABSTRACT This paper presents the derivation of the intensity–duration–frequency (IDF) curves for the Kingdom of Saudi Arabia. Such curves were obtained based on rainfall events measured in 28 meteorological stations distributed throughout the Kingdom. For 20–28 years period, 2027 rainfall storms of durations ranging from 10 min to 24 hours were collected and analyzed. Both Institute of Hydrology model (IH-Flood) and Excel-sheet program are used for developing IDF equations for every station. The method of least squares was used to get relationships for the parameters of the IDF formulas. The calculated goodness of fit shows strong correlations range between 0.99 and 0.98 for one of the parameters, and between 0.92 and 0.74 for the other parameters and thence indicating robust IDF formulas for practical use. Regionalization of the IDF parameters for the 13 distinct regions of the Kingdom has been developed. In addition, an average of IDF parameters is made over the Kingdom as a whole to be used in regions of no rainfall records. The resulting IDF curves are usually used for flood estimation in urban/rural watersheds. Using the resulting IDF curves is highly recommended for rigorous, efficient and safe design of hydraulic structures and flood protection works.

Generation of Rainfall Intensity Duration Frequency (IDF) Curves for Ungauged Sites in Arid Region

ObjectiveWe developed a method for Intensity Duration Frequency (IDF) curves in ungauged locations in arid region.BackgroundThe arid climate which covers most of Saudi Arabia is typically characterized by large temporal and spatial variations in rainfall distribution. The availability of long-term records of rainfall-runoff series would be useful to better estimate effective rainfall depth. The development process for an IDF curve for a remote, ungauged site is addressed through the use of rainfall record.MethodThe analyses focused on the application of two distributions: the Gumbel and Log Pearson III functions combined, to estimate the maximum rainfall for the various return periods in three stations in Al-Madinah region.ResultsThe empirical intensity frequency equation is used to estimate rainfall intensity for design purposes for the ungauged location. The results of this research contribute to the development of IDF-based design criteria for water projects in ungauged sites located in arid and extreme arid regions.