Journal of Irrigation and Drainage Engineering

To promote water control in coastal areas developed for agriculture, tidal hydraulic structures (doors and flap gates) are used for the hydraulic management of irrigation and drainage networks. By closing when the water level increases due to the tide, they prevent sea water inflow. However, fish using the tidal wave to move forward (e.g., glass eels) are also blocked from accessing the hydrologic network. There are hydromechanical solutions to mitigate these problems, such as adding a wooden block to leave an opening at high tide or adding a spring to delay the closing of the structure. The latter solution allows the structure to remain open only during a part of high tide. Designed empirically, these solutions can either alter the hydraulic control performance or be insufficiently effective for fish passage. This study proposes an operating model approach for hydromechanical structures that takes these passage solutions into account. This approach makes it possible to evaluate the performance of the passage solutions for fish passage and hydraulic regulation. With the help of these models, it is possible to design solutions that ensure a compromise between the passability of fish species and agricultural uses.

Although waterway connectivity is a requirement for all freshwater fish, culverts have had negative impacts on freshwater river ecology. Following a recent biological study suggesting that asymmetrical wall baffles may be conducive to upstream passage of small-bodied fish, experimental modeling of plain wall baffles on one sidewall only was conducted under controlled flow conditions. The measurements were performed in a 15-m-long, 0.5-m-wide culvert barrel channel at several longitudinal and transverse locations for a broad range of discharges and baffle geometries to deliver a fine characterization of the hydrodynamics of the asymmetrically baffled channel. The physical modeling data illustrated the drastic impact of a seemingly simple boundary treatment (i.e., plain rectangular baffles) on the flow field. In practice, the installation of baffles has practical engineering implications that must not be ignored.

In-stream low-head hydraulic structures are eco-friendly solutions to maintain the natural aquatic ecosystems. This study focused on scour characteristics around double-winged log -frames under different hydraulic conditions and structure configurations, including stone-reinforced structures. Three types of equilibrium scour morphologies were distinguished for each tested configuration. Generally, two scour formations occur upstream and downstream of the structure, depending on its configuration. Empirical equations are proposed to predict maximum depth and other characteristic lengths of the scour hole and dune. A new equivalent densimetric Froude number was derived by dimensional analysis. The equations were validated with data pertaining to similar structures. Overall, this study shows that double-winged log frames are suitable for creating resting pools for fish species, and can contribute to enhance bank stability. Although the analysis was limited to straight channels, the proposed design equations represent the first quantitative tool to assess scour features for this structure typology.

A steady-state analytical solution is proposed for computing three-dimensional seepage into a partially penetrating ditch drainage system receiving water from an uneven ponding field of finite size. The draining soil is assumed to be saturated, homogeneous, and anisotropic, resting on an impervious stratum. The correctness of the proposed model was checked with the analytical and experimental results for a simplified case. A numerical comparison was also carried out between the proposed analytical model and the corresponding finite-difference model for a given flow condition. The study highlights the significance of drain width, penetration depth, ponding distribution, and anisotropic ratio on the discharge distribution from the side and bottom face of the drains. In ditches of shallow depth, a significant rise in the percentage of bottom flow was found in soil with a low anisotropic ratio. With the introduction of the uneven ponding field, considerable enhancement in the contribution of flow discharge from the bottom face of the drain was observed. Travel time and orientation of flow paths were found sensitive to the point of release at the soil surface. Moreover, partially penetrating ditches promote a highly curved flow path from the surface to the recipient drain which in turn increases the travel time of the water particle.

Previous research has identified five canonical rainfall distributions in the United States; however, identification of these rainfall distributions did not include any rainfall data in the state of Texas. In this study, data from 813 rainfall stations in Texas are used to update the canonical distributions, which are then extended to include Texas. Canonical rainfall distributions are extracted using cluster analysis, which identifies distinct rainfall distributions that are not statistically different from measured rainfall distributions. Novel findings of this study are that the canonical intensity-duration functions for all canonical rainfall clusters in the United States can be expressed in a single functional form, and the canonical rainfall distributions and canonical intensity-duration functions are not very sensitive to return periods in the range of $5–25\mathrm{years}$, with the effect of the return period being mostly accounted for in the specification of the $24\text{-}\mathrm{h}$ rainfall amount.

Slide gates are commonly used to adjust flow in open canals. The discharge coefficient ($C_d$) for a slide gate is a function of the gate’s geometric and hydraulic characteristics. For free flow conditions, $C_d$ depends on the upstream water level and the opening of the gate, whereas for submerged flow, it also depends on the downstream water level. The main aim of this study is to conduct a series of laboratory experiments to determine $C_d$ for inclined slide gates. These tests and models were used to evaluate both free and submerged flows. Experiments with inclination angles of 0°, 15°, 30°, and 45° were studied with different gate openings. The collected data are used to develop equations for predicting $C_d$. The results show that the inclination of the slide gates has a progressive effect on $C_d$ and increases capacity under the gate. The increase in $C_d$ relates to the convergence of the flow through the gate opening. The produced equation via genetic programming with $R^2$ and a relative error of 0.9431 and 0.0014 had optimal efficiency compared with classical multiple regression models. A comparison with other studies for inclination angles of 45° and 60° was also conducted.