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Climate variability and change significantly influence crop water demand by affecting crop coefficient (K c ), reference crop evapotranspiration (ET o , a grass reference) and potential crop evapotranspiration (ET c ). The climatic effects on these hydroclimatic parameters were investigated in the past mostly for the entire crop growth period, but little or no information is available on their variation over different growth stages of the crops, specifically in Bangladesh. Therefore, this study intended to evaluate the climatic effects on these hydroclimatic parameters at the initial, development, midseason and late-season growth stages of two rice varieties (Bangladesh Rice Research Institute [BRRI] dhan28 and BRRI dhan29) dominantly grown in the dry season in two northeast districts/subdistricts (Sylhet and Srimongal) as well as many other districts of Bangladesh. K c , ET 0 and ET c were analysed for the period from 1994 to 2015 using the analytical approach of the Food and Agriculture Organization (FAO) Penman-Monteith method. The results revealed that the K c of the rice varieties increased in all growth stages over time, with the maximum K c (1.247) in the mid-season stage in Srimongal. ET o and ET c were found to be maximum in the mid-season and late-season stages, respectively. The potential crop water demand (CWR pot ) greatly varied among the initial and development stages and between the two rice varieties. The initial and mid-season growth stages of rice required more water than the other growth stages. The results on the growth stagewise variation of the hydroclimatic parameters pertinent to rice cultivation may greatly contribute to irrigation scheduling for dry-season rice cultivation and planning water resources in the study region.

There are multiple initiatives aimed at strengthening coastal communities against tsunami disaster risks, such as growing vegetation belts, construction of embankments, moats, and different hybrid alternatives. To find a solution for strengthening the coastal buildings themselves, we firstly reviewed the flow phenomena around a single emergent (circular and rectangular) cylinder (case C1), which was considered as a piloti-type column under different Froude conditions, and evaluated the formation of surface bow-waves, hydraulic jump detachment, and wall-jet-like bow-waves. Secondly, the flow characteristics were investigated under the same Froude conditions with side-by-side two-cylinder (case C2) and four-cylinder (case C4) arrays in an open channel. Surface bow-wave length (LBw) increased by 7–12% over the rectangular cylinders (RCs) compared to the circular cylinders (CCs) with a subcritical flow. For the supercritical flow with a 1/200 bed slope, hydraulic jump detachment was observed in relation to the Froude number. The observed length of the hydraulic jump detachment (Ljump) varied between 3.1–8.5% and 4.2–12.9% for the CCs and RCs in the supercritical flow with a 1/200 bed slope. In addition, the wall-jet-like bow-wave height (hjet) over the CCs was increased by 37% and 29% compared to the RCs with a supercritical flow and zero bed slope (orifice-type flow). For case C4, a hydraulic jump was observed for the supercritical flow over the horizontal channel bed. Finally, empirical equations were defined concerning the geometrical shape and arrangement based on the experiment data for the single and side-by-side configurations of the cylinders to validate the height of the wall-jet-like bow-wave as the most critical flow property.

Coastal embankments often collapse due to the tremendous destructive energy of an overtopping tsunami flow due to a deep scour by nappe flow. Hence, to clarify the nappe flow formation condition due to the overtopping, a series of tests were carried out within a laboratory flume with immobile settings by lowering the downstream surface angle of an embankment model while keeping the upstream surface slope constant (1:1) with five non-dimensional overtopping depths and six different crest conditions. The conditions imposed on the embankment crest in the flow direction were without vegetation; horizontal crest, (−)4% descending crest slope, (+)4% ascending crest slope, and adding vegetation model with three different densities across the horizontal crest to improve resistance to the flow. The increased resistance provided by the vegetation models were categorized based on the spacing ratio between cylinders to diameter: sparse, intermediate, and dense. Increased vegetation density above the crest results in a significant reduction of flow energy by approximately 30–50% at the downstream brink edge and 40–60% at the downstream plunge basin. In contrast, the maximum energy reduction was found to be by the dense vegetation model. Additionally, owing to the steep slope of the water surface profile and the increasing vegetation density, the impinging jet’s impact point moved closer to the toe of an embankment. This implies that vegetation covers a smaller area while increasing density to mitigate the destructive intensity of flood/tsunami movement. Meanwhile, the descending crest scenario results in a faster nappe flow formation. In contrast, the ascending crest scenario delays the nappe formation while reducing the downstream slope angle. It maintains the sub-critical flow at the crest, except near the downstream brink edge.