Suchergebnisse

It is recognised that the hydrological and erosion processes in watersheds are very much conditioned by the (inter)action of a number of variables. This paper covers a 15-year period of studying those factors that have a major influence on the sediment yield and transport during individual hydrological events in a small Mediterranean agricultural watershed. Multivariate statistical techniques such as cluster analysis and principal component analysis were applied for the interpretation of datasets. In addition, the relationships between suspended sediment concentration and discharge (hysteretic loops) were also analysed. The hydrological response of the studied watershed is mainly controlled by the antecedent condition of the flow. Most of the runoff and sediment are generated during the wet season when vegetation cover is scant and saturation overland flow occurs promptly as a response to almost any rainfall events. In contrast, during the dry seasons even if high-intensity rainfalls normally occur, very scant runoffs are, however recorded, at the exit of the watershed. Most of the eroded sediment seems to come from riparian areas. The discharge registered at the watershed outlet up to 1 h prior to the flood is a very good surrogate for antecedent soil moisture. ; This study was partly funded by the Spanish Government's National Scientific Research, Development and Technological Innovation Plan, both project code CGL2007-63453 and project code CGL2011-24336. The authors also acknowledge the generous contribution of the Department of Rural Development and Environment of the Government of Navarre (Spain).

Abstract. The ability to understand and predict coarse-sediment transport in torrent catchments is a key element for the protection against and prevention of the associated hazards. In this study, we collected data describing sediment supply at 99 torrential catchments in the northern French Alps. The sample covers a wide range of geomorphic activity: from torrents experiencing debris flows every few years to fully forested catchments exporting small bed load volumes every decade. These catchments have long records of past events and sediment supply to debris basins. The mean annual, the 10-year return period and the reference volume (i.e., the 100-year return level or the largest observed volume) of sediment supply were derived for the studied torrents. We examined the relationships between specific sediment supply volumes and many explanatory variables using linear regression and random forest approaches. Results showed that the ratio of sediment-contributing area (bare soil or rock) to catchment area is the most important predictor of the specific sediment production volumes (m3 km−2). Other variables such as the Melton index or the indices of sediment connectivity also have an influence. Several predictive models were developed in order to estimate the sediment supply in torrents that are not equipped with debris basins.

This study aims to assess the suitability of the sediments present in Tigris River, Tikrit city, northern Iraq for concrete production and road building purposes. Representative samples were collected from three selected stations at the study area using the channel modeling method. According to the grain size analysis, the sediments were classified as a type of poorly graded gravels (GP) depending on the unified soil classification system. The true specific gravity of the soil ranged between 2.28 and 2.568. The chemical analysis of the study samples revealed that gypsum content ranged between 0.82 and 1.69 %. Total soluble salts ranged 2.45- 3.87%, the organic matter content ranged 0.14- 0.76%, and the pH value was between 7.73 and 7.38%. The results of the Los Angeles Abrasion Test of selected samples showed weight loss ratios for the three stations (1, 2, and 3) of 19.9, 20.7, and 17.2%, respectively, while the maximum dry density values were 2.2739, 2.1940, and 2.2013 gm / cm3, respectively. The values ​​of the Californian Bearing Ratio test (C.B.R) were 53, 65 and 106 %, respectively. After comparing the results with the standard values of ASTM for concrete and roads materials, it was found that the samples were suitable for these purposes.

This book elucidates the vital but often neglected relationship between bottom soil and water quality. An understanding of this important connection is essential for maintaining water quality within optimum ranges for shrimp and fish. It is the first volume to provide information on topics from soil science essential to pond aquaculture. The impact of soil-water interactions on water quality is examined, and the volume provides important methods for enhancing the soil conditions in ponds. Detailed chapters include coverage of *soils in pond aquaculture *physical, chemical, and mineralogical properties of soil *soil nutrients *the exchange of dissolved substances between soil and water *soil organic matter, anaerobic respiration, and oxidation-reduction *sediment soil *relationships to aquatic animal production *pond bottom management and soil analyses. Bottom Soils, Sediment, and Pond Aquaculture gives students and professionals in aquaculture insight into the principles of soil science which most affect pond management and provides them with an essential and current reference