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Ring footing represents a significant structural member in different applications such as fuel or water storage tanks in addition to other structures. The advantage of this type of footing is related to the ability to reduce the weakness of some soils that may affect the safety of structures. An experimental testing program was conducted by using a small-scale model in the laboratory of the college of engineering at the university of Al-Mustansiriyah which consists of twelve ring footing models resting on loose sand reinforced by geogrid layers. The parameters that studied in this research are the diameter of ring footing, thickness of ring, the position placed of one reinforced layer and vertical spacing between two reinforced layers. The findings of this research shown that the optimum percentage of diameter ratio of ring footing is (0.25) and when the depth-ratio increases, the bearing-capacity of ring footing begin decreases. In general, the increase in ring thickness causes the bearing-capacity and the rigidity of ring foundation to increase. The optimum of the depth-ratio of the first reinforced layer is (0.25) and the optimum value of vertical-spacing bounded by layers is around (0.25) which produces a maximum value of the bearing-capacity. Its noticed that when these percentages exceeded value 0.25, the bearing-capacity of the ring foundation drops eventually.

Tigris River is the only potable source in Baghdad city therefor many water treatment plants were built on the banks such as Al-Karkh, Sharq Dijla, Al-Sadr, Al-Wathba, Al-Karama, AlQadisia, Al-Dora, Al-Wahda, and Al-Rashed project. Tigris River suffers from the pollution that comes from various sources such as Industry, domestic sanitation, and farming activities therefore several indices were used to calculate water quality within Baghdad to convert physicochemical parameters of water to a single value that represents the river status (good, bad, very bad, etc..). The aim of this review paper to show the results of previous studies about the water quality for the Baghdad region. Most results showed that water quality was good in the north of the city of Baghdad and bad in the south of Baghdad. The deterioration of water quality was due to many reasons such as the discharge of wastewater directly into the river without pretreatment, increase in (Eclectic conductivity, Turbidity, and total suspended solids, total hardness, Iron ion, the fecal coliform) concentrations, and Climate change, therefore, Tigris River needs intensive treatment before using by humans.

The use of raw white eggshells (WES) as a catalyst, and promoted WES with acetic acid as a promoted catalyst for study the adsorption of cobalt (CO+2) and lithium (Li+) ions from polluted soils was investigated in this paper. The selection of a treated chemical substance was achieved after performing several experiments under controlled laboratory conditions using three chemical substances covering different range of pH: acidity (acetic acid), neutral (potassium iodide), and alkalinity (baking soda) media to determine the optimal conditions for improving CO+2 and Li+ recovery from soil contaminated samples. Several operating factors were examined in order to detect their corresponding effects on the catalyst behavior. These factors were: pH, incubation time, the initial concentration of CO+2 and Li+ ions, the dose of the WES, and the ambient temperature. The maximum adsorption efficiency of CO+2 and Li+ions were 94 and 85% for promoted WES at the incubation time of 21 and 7 days, pH of 5 and 4, temperature of 50 and 45 °C, and WES dose of 2.5 and 3 g, respectively. A regression equation was developed to investigate the removable percentage for both pollutants at different dosage of ordinary WES. This method introduces an innovative idea for promoting the process of remediation of light and heavy metals using a low-cost adsorbent under controlled laboratory conditions.

Pooled step cascade weirs are hydraulic structures that are preferred over ordinary weirs due to their application on steep slopes and to their effectiveness in obtaining water aeration. However, these structures are subject to failure due to scour being initiated downstream, or to breakdown due to the high energy of impinging water. In this paper, an experiment was presented to study the effect of the number and ratio of holes in weirs to improve energy dissipation. To improve energy dissipation, cascade weirs with different configurations of openings were proposed. Furthermore, a sluice gate at the upstream of a cascade weir was proposed as a new technique to increase energy dissipation and reduce scour at downstream. Ten models of pooled step cascade weirs (nine models with different hole configurations and one with a sluice gate upstream), in addition to the ordinary weir, were constructed to investigate the effect of the sluice gate and holes on energy dissipation; the range of each type of flow (nappe, transition, and skimming); the relevant Froude number; and the ratio of water depth to critical depth over pooled step cascade weirs. To implement this, the ratio of holes to the area of the weir were between 0 and 21.22% and the number of holes used were one hole, two holes, and three holes. The results concluded that the best method to obtain maximum energy dissipation was putting a sluice gate at the upstream of a solid pooled step cascade up to a discharge of 2.0 l/s. The most effective ratio of holes to weir area was 7.15% at the minimum Froude number when the discharge exceeded 2.0 l/s. Moreover, the ratio of upstream water depth to critical depth decreased with increasing discharge. The nappe, transition, and skimming flow types were increased more on a pooled stepped cascade weir of 7 mm opening diameter with three holes (ratio of 7.15%) than the other models. The Froude number decreased as the hole numbers increased at high discharges for the pooled stepped cascade weir, especially with the hole diameter of 12 mm. Some empirical equations were established to represent the relation between the upstream head and discharge for each case.

The benefit of using a weir is that it allows flowrates to be measured and controlled in open channels and streams. The objectives of this research are: (1) to specify a suitable crest depth position as a control section for estimating the flowrate above a curved crump weir at ten different longitudinal slopes and (2) to compare the proposed flowrate versus measured and computational fluid dynamics (CFD)-simulated flowrates. In this research, the crest point of the curved crump weir was considered to be a control section, relating to the critical depth as a function of the crest depth. Experiments with eight different laboratory flowrates of flume were proposed at ten different channel slopes ranging from 0.0 to 2.5%. Statistical analysis of linear regression indicated that the relationship between critical depth and crest depth is 0.913 on average. Based on this finding, a new equation was derived to predict the discharge over the crump weir, which indicated an excellent match compared to the practical and CFD-simulated results (a maximum differences of 4% based on several standard error indexes and a one-way ANOVA). The CFD technique was performed to simulate the velocity and flow pattern of the curve crump weir based on the volume of fraction method. Six selective sections were tested along the flume with a total length of 1.36 m for a case study of 0.912 m3/h flowrate and zero bed slope to investigate and describe the water surface profile. The statistical analysis indicated insignificant differences between the measured and simulated water surface profiles, with a maximum difference of less than 15% observed at the section located at 0.69 m, while the average difference was 4.86% for all sections.

The use of theoretical models, with multiphase flow (air, water, and sand), is lacking in prior research for the simulation and management of erosion around hydraulic structures. In this research, flume experiments and a Computational Fluid Dynamic (CFD) model were used to study flow properties and scour around four new shapes of submerged weir: inclined sharp crested weirs with 30° and 120° slopes, respectively, and two different vertical arch weirs. The proposed weir shapes were compared against a sharp crested weir to investigate any potential reduction in scouring at different discharges. The results showed that the inclined sharp crested weir with a 120° angle reduced the maximum scour depth by more than three times compared to the sharp crested weir. The results also indicated that there was a statistically significant difference between the CFD simulation and the flume experiments for both the sharp crested weir and the inclined weir with a 120° angle. This research supports the design and use of inclined weirs with 120° angles for the alleviation of scour around hydraulic structures. Keywords: Submerged weir, Multiphase flow, Scour depth, Flume experiments, CFD

Backwater rise is a function of flow properties, fluid characteristics, and channel geometries. Flume experiments were conducted to investigate the effect of the permeable spur dike dimensions (blockage ratios of 45% to 77%) and diameters of mono-size glass beads (7.4 mm to 26.0 mm) on the backwater rise in open channel subcritical flow. Dimensional analysis was performed to correlate different variables affecting the flow hydraulics. Flow rates of 15 and 30 m3/h were used with each spur dike size and diameter. Results show a linear relationship between the Froude number and backwater rise downstream the spur dike. High upstream water levels were observed as the blockage ratio decreased. A coefficient shape of 0.48 was suggested for permeable rectangular spur dikes using Yarnell’s equation for backwater rise with no statistical analysis differences between the measured and predicted data. Dimensional analysis was applied to predict the upstream (u/s) water levels for all models, exhibiting an excellent agreement between the measured and predicted water levels, with R2 of 0.98.

Recent studies have investigated the influence of Iraqi stabilizer materials on the stability of artificially lead-contaminated soil. Prior research has not been able to predict the non-linear erodibility model (Wilson model) of mechanistic parameters (b0 and b1) from jet erosion tests (JETs) due to lead-contaminated soil treated with different stabilizers. The aims of this research are to 1) mathematically evaluate the detachment parameters (b0 and b1) of the Wilson model from JETs of lead-contaminated soil samples treated with different percentages of three common Iraqi stabilizers (lime, cement, and bitumen) at different curing times (24 hrs, 72 hrs, and 168 hrs), and 2) to develop relationships between the parameters, b0 and b1, in addition to the physical and chemical soil characteristics. JETs are utilized to determine the mechanistic erodibility parameters b0 and b1 from observed scour data of packed contaminated soils at optimum soil moisture level. The results show that observed scour depths are reduced for treated lead-contaminated soils in JET experiments. The observed b1 values increased at different curing times, while a significant reduction in b0 is observed. The proposed formulas are able to mathematically predict the influence of different stabilizers on the mechanistic erodibility parameters (b0 and b1) of treated contaminated soils with a prior JET experiment based on stabilizer coefficients.

The Ilisu Dam is part of the Turkish Southeastern Anatolia Project (GAP) and is the largest dam on the Tigris River in Turkey. It is located on the main river course 65 km upstream of the Syrian and Iraqi border. The Ilisu Dam watershed is the same as that of the Mosul Dam in Iraq. Sharing the same watershed with the Mosul Dam and located upstream, the Ilisu Dam will usurp most of the watershed and deprive the Mosul Dam of most of its current inflow. This paper presents an assessment of the hydrological impact (basically predicts changes on future inflow) of the Ilisu Dam on the Mosul Dam. The assessment is based on the worst-case scenario. The analyses that are employed include geographic information system (GIS) techniques and regression models, along with statistical analyses to numerate expected future impacts on the Mosul Dam’s inflow distribution. Results reveal that the Ilisu will have a drastic impact on the inflow regime of the Mosul Dam. A reduction as high as 78% of the inflow of the Mosul Dam may occur if the operation of the Ilisu and the Cizre Dams is conducted with no consideration of downstream hydrological and environment impacts.

Large amounts of runoff is generated in western Iran and flows into eastern Iraq due to relatively intensive rainstorms along the international border line. Currently, most of this runoff is being wasted by evaporation instead of being stored and preserved for later uses. This paper is an attempt to (1) assess and harness the water resources of eastern Iraq, and (2) propose a storage scheme to use the harvested water in the water shortage times. The runoff of eight catchment areas (Mandali, Qazania, Tursaq, Mirzabad, Galal Badra, al-Chabbab, al-Teeb, and Dwaireeg) is estimated using regression equations derived for areas in the western and southern parts of the United States of America. Several models were selected from two states based on catchment area location, average terrain elevation, average annual precipitation, and slope of main stream. Observed runoffs of Tursaq, Galal Badra, and al-Chabbab streams are analyzed using normal probability plots. Statistical analysis shows that there is no a statistically significant difference between observed and predicted runoffs for different return periods. The study proposes a water reservoir to be constructed within al-Shiwiaja Marsh to accommodate runoff generated within Mandali, Qazania, Tursaq, Mirzabad, and Galal Badra streams. The capacity of the proposed reservoir is 3000 Mm3 and the expected inflow from these streams is projected to exceed the capacity of the reservoir. The proposed reservoir will contribute to the flow of the River Tigris during the non-rainy seasons. More studies are needed to propose and design a storage scheme for two remaining streams (al-Teeb and Dwaireeg).

The quality of groundwater is a global concern that is usually assessed using quality indices. The Canadian Water Quality Index (CWQI) alongside with Geographical Information system (GIS) were adopted to evaluate the quality of Kirkuk’s groundwater in terms of its suitability for drinking, irrigation, aquatic, recreational purposes, and livestock uses, in 60 wells within the time period of 2017 to 2019. The groundwater quality was assessed depending on Iraq’s and world health organization (WHO) guidelines. The Iraqi standards were used for drinking purposes. The WHO standards were used for irrigation, aquatic, recreational, and livestock purposes. Both standards were incorporated in CWQI Excel Spreadsheet to evaluate the groundwater quality for studied wells. Samples were collected and analyzed for 15 major parameters. According to the CWQI, groundwater samples obtained were classified as marginal in 2017 and 2018; while poor water for drinking was observed in 2019.

In the present study, this work investigated the effects of bacteria (Bacillus sp.) decay and biological aggregating factors (organic matter, microbial calcium carbonate precipitation) at various steps on soil aggregate stability. Experiments carried out at different cultivation time 2, 5, and 8 weeks. The soil samples were compared the control (pure soil) versus soil treated with bacteria. The results showed that bacterial activity played an essential function in the macro-aggregate foundation. Nevertheless, the influence of organic matter (OM) on soil aggregate stability was important, which might be related to the microbial activity of bacteria to decay the organic material to an organic mineral that is connected with soil particles to form stable micro-aggregates. The CaCO3 is one of the most stable bonding agencies in nature as it is called natural cement, The soil aggregates stability increased as calcium carbonate increased. No change of soil pH levels observed due to microbial reactions with soil. Hence, the appropriate pH was 7.5. In addition, the higher pH decreases enzymatic activity and carbonate tends to dissolve at pH levels are very low. This study affords the helpful of soil stabilization in the presence of natural cementation of bacteria in contrast with the previous studies.

Recently, water quantity is decreasing due to high temperatures in summer and reducing the water quotas of Euphrates River in Iraq from the neighboring countries. These factors may increase turbidity and concentration of elements in Euphrates River especially near Alhindya Barrage, Babylon Governorate, Iraq. Thus, Euphrates River may not be valid for drinking and irrigation purposes in upstream of Alhindya Barrage. The aim of this study was to investigate the water quality upstream of Alhindya Barrage, Euphrates River, using Canadian Water Quality Index (CWQI). The comparison of water quality was investigated in the years of 2008 and 2009 according to data availability. Statistical analysis were performed on measured flowrates and indicated that there is a statistically significant difference between measured flowrates for 2008 and 2009. The results showed that the CWQI of 2008 was 94 which is good to excellent water quality, compared to CWQI of 79 for 2009. This was due to reduction in mean water quantity from 370m3/s of 2008 to 213m3/s of 2009. The global warming phenomenon is the main reason for dry seasons and low rainfall intensity and caused bad water quality.

Biological soil crusts (biocrusts) are generally found in many landscapes. Biocrusts are known to have a key role in terms of soil stabilization but the mechanism of biocrusts is poorly understood. Thus, this work intends to examine the impact of two biocrusts: Cyanobacteria and Chlorophyte, on parameters of cohesive soil erodibility (erodibility coefficient, kd, and critical shear stress, τc) using a small-scale form of Jet Erosion Test (mini-JET) at different drying times. In addition, the study aims to develop relationships between τc and kd versus certain soil characteristics. Eighteen undisturbed soil samples of two biocrust types Cyanobacteria, and Chlorophyte, and bare soils were acquired from the banks of the Tigris River in Iraq, and were tested in a laboratory using a mini-JET at drying times of 5, 8, and 12 days, in order to mimic field conditions. It was observed that dead algae still adhered to and bound soil particles together throughout the observation period, which contributed to soil stability, and increased moisture and nutrient retention before decomposition. As the drying times increased in the two biocrusts, the statistical results showed a reduction in kd, while τc values increased. The kd decreased as salt concentration, organic matter, and calcium carbonate increased, while the τc increased. No change in pH levels of soil was observed due to the reactions in the biocrusts between the algal crust and soil particles, which increased organic matter and calcium carbonate. This study discusses the benefits of using a JET instrument; including reducing testing time, conserving energy, and providing low-cost method for observation of crusted soil stabilization, in comparison with previous techniques.

A huge retreat on Tigris Riverbanks of Numaniyah-Kut reach was recently investigated in Southeast Baghdad, Iraq. Riverbank retreat due to both fluvial erosion and geotechnical failure was recently ...

Typically the erosion rate of cohesive soils is modeled using the excess shear stress equation, which includes two soil parameters: the erodibility coefficient ( k d ) and the critical shear stress ( τ c ). Alternatively, a mechanistic detachment rate model, the Wilson model, was recently developed to predict the erosion rate of cohesive soils, also based on two soil parameters: b 0 and b 1 . The Wilson model is proposed as advantageous in terms of being a more mechanistic, fundamentally based erosion equation. The objective of this research was to derive the excess shear stress model parameters ( k d and τ c ) from field jet erosion tests (JETs) on numerous streambanks across the Illinois River watershed in Oklahoma to investigate (i) erodibility parameter variability or uniformity at a river basin scale, (ii) correlations between the derived parameters and soil texture, (iii) influence of solution technique on the estimated erodibility parameters, and (iv) the applicability of predictive relationships between k d and τ c . The second objective was to demonstrate the applicability of the mechanistic Wilson model using field JET data and to investigate correlations between the excess shear stress model parameters, k d and τ c , and the Wilson model parameters, b 0 and b 1 . Erodibility parameters for streambanks of varying soil texture were measured using a miniature version of the JET device (mini JET). Data from the JETs were used to derive the erodibility parameters using a Blaisdell and scour depth approach. Soil samples were acquired at locations of the JETs to quantify particle size distribution, average particle size ( d 50 ) and bulk density. No significant relationships existed between k d or τ c and bulk density, d 50 , percent clay, silt, or sand, or percent clay-silt. Existing empirical relationships should be used with caution considering the variability between the results observed in this research and previous relationships proposed in the literature. Strong correlations were observed between b 0 and k d ( R 2 = 0.62 to 0.89) and between b 1 and τ c ( R 2 = 0.31 to 0.96). Therefore, the Wilson model parameters closely resemble the empirical excess shear stress parameters.

The erosion rate of cohesive soils due to fluvial forces is usually computed using an excess shear stress model. However, no mechanistic approaches are available for incorporating additional forces, such as seepage, into the excess shear stress model parameters. Recent research incorporated subsurface (seepage) forces into a mechanistic detachment rate model for streambeds. The new detachment model, the Modified Wilson model, was based on two modified dimensional parameters (b 0 and b 1 ) that included seepage forces. The objective of this study was to modify the parameters (b 0 and b 1 ) to quantify the influence of seepage on erodibility of cohesive streambanks and to compare the results to those obtained from tests on horizontal beds. A new miniature version of a submerged jet erosion test device (“mini” JET) and a seepage column were utilized to derive the parameters of the Modified Wilson model for a silty sand soil and a clayey sand soil across a range of uniform seepage gradients. The experimental setup was intended to mimic a streambed and a streambank when the “mini” JET and seepage column were placed in vertical and horizontal orientations, respectively. The soils were packed in a standard mold at a uniform bulk density (1.5 to 1.6 Mg m -3 ) near the optimum water content. Seepage forces influenced the observed erosion with a non-uniform influence on b 0 and b 1 as functions of the hydraulic gradient and density. Expected theoretical differences between Wilson model parameters for streambanks and streambeds were not consistently observed for these erodible soils, most likely due to variability in streambed and streambank samples in terms of soil preparation, packing, and seepage gradient establishment. The influence of seepage forces can be predicted by the Modified Wilson model parameters in both vertical and horizontal experimental setups using JETs on soils without seepage. Additional research is needed on the behavior of several mechanistic soil parameters under the influence of seepage.

Many factories and hospitals dumped their wastewater into Tigris River without any treatment in Baghdad city. This could influence on soil erodibility on Tigris Riverbanks. Phenol, Nitrate, and Phosphate were considered as huge concentrations in wastewater chemicals. The main objectives of this research were: 1) to investigate the influence of three wastewater chemicals on erodibility parameters of cohesive soils using Blaisdell's solution and scour depth solution techniques from jet erosion tests (JETs); 2) to develop relationship between erodibility parameters and soil hardness. An excess shear stress model was utilized to measure soil erodibility based on two empirical soil parameters: critical shear stress (τc) and erodibility coefficient (kd). The results showed a constantly increased in kd for all three wastewater chemicals at different curing times and concentrations, while τc values were decreased. An inverse relationship was developed between τc and kd for both Blaisdell's solution and scour depth solution techniques.

Typically the erosion rate of cohesive soils is modeled using the excess shear stress equation, which includes two soil parameters: the erodibility coefficient (k d ) and the critical shear stress (I„ c ). A jet erosion test (JET) is a standardized method available for deriving the erodibility of cohesive soils. The JET data are typically analyzed using a Blaisdell solution approach. A second solution approach based on direct parameter optimization to the measured scour depth data has recently been proposed but with limited evaluation. Therefore, the objectives of this research were to: (1) develop a new spreadsheet tool that simultaneously solves for the erodibility parameters using both solution approaches, (2) evaluate the solutions in terms of their ability to predict the observed scour depth data, and (3) quantify differences in the predicted erodibility parameters from the two approaches. A series of JETs conducted across the Illinois River watershed in eastern Oklahoma were used to evaluate the performance of the spreadsheet and the solution methodologies. The new scour depth solution provided improved fits to the original scour depth data along with being more stable in converging to a solution as a function of the initial parameter estimates. The automated spreadsheet provides an easy-to-use tool for deriving erodibility parameters from JETs.

Mechanistic models have been proposed for soil piping and internal erosion on well-compacted levees and dams, but limited research has evaluated these models in less compacted (more erodible) soils typical of hillslopes and streambanks. This study utilized a soil box (50 cm long, 50 cm wide and 20 cm tall) to conduct constant-head, soil pipe and internal erosion experiments for two soils (clay loam from Dry Creek and sandy loam from Cow Creek streambanks) packed at uniform bulk densities. Initial gravimetric moisture contents prior to packing were 10, 12 and 14% for Dry Creek soil and 8, 12, and 14% for Cow Creek soil. A 1-cm diameter rod was placed horizontally along the length of the soil bed during packing and carefully removed after packing to create a continuous soil pipe. A constant head was maintained at the inflow end. Flow rates and sediment concentrations were measured from the pipe outlet. Replicate submerged jet erosion tests (JETs) were conducted to derive erodibility parameters for repacked samples at the same moisture contents. Flow rates from the box experiments were used to calibrate the mechanistic model. The influence of the initial moisture content was apparent, with some pipes (8% moisture content) expanding so fast that limited data was collected. The mechanistic model was able to estimate equivalent flow rates to those observed in the experiments, but had difficulty matching observed sediment concentrations when the pipes rapidly expanded. The JETs predicted similar erodibility coefficients compared to the mechanistic model for the more erodible cases but not for the less erodible cases (14% moisture content). Improved models are needed that better define the changing soil pipe cross-section during supply- and transport-limited internal erosion, especially for piping through lower compacted (more erodible) soils as opposed to more well-compacted soils resulting from constructing levees and dams. Copyright © 2013 John Wiley & Sons, Ltd.

Typically soil erodibility is quantified using an excess shear stress equation, dependent on two major soil parameters: the critical shear stress (I„ c ) and the erodibility coefficient (k d ). A submerged jet test (JET, Jet Erosion Test) is one method that has been developed and methodology of use established in the literature for measuring these parameters. In this study, a new miniature version of the JET device (“mini” JET), with the advantage of being easier to use in the field, was used to measure I„ c and k d for two soils (silty sand and clayey sand), and results were compared to the larger original laboratory JET. The objective of this research was to determine if the “mini” JET measured equivalent values for I„ c and k d compared to the original JET device. In-order to compare the performance and repeatability of both JET devices, tests were performed on paired samples prepared in the same way and tested at the same time. Samples of the soils tested were prepared at different water contents with a standard compaction effort of 600 kN-m/m 3 (ASTM). Some variability in measuring I„ c and k d was observed between paired samples due to variability in the soil texture of the soil samples and differences in soil moisture levels. The k d values measured by the two JET devices for both soils were not significantly different. The I„ c values measured by the “mini” JET were consistently lower than those measured by the original JET. This was hypothesized to be due to the structure of the soil sample due to the compaction method and the procedure utilized to determine I„ c . Adjustment of the equilibrium depth of the “mini” JET resulted in small differences in the estimated I„ c between both JET devices. Both JET devices also demonstrated consistent performance in measuring I„ c -k d relationships, which were compared with those observed in previous field research.

The erosion rate of cohesive soils is commonly quantified using the excess shear stress model, which is dependent on two major soil parameters: the critical shear stress (I„ c ) and the erodibility coefficient (k d ). A submerged jet test (jet erosion test, or JET) is one method that has been developed for measuring these parameters. The disadvantage of using the excess shear stress model is that parameters I„ c and k d change according to erosion conditions, such as soil structure, soil orientation, type of clay, presence of roots, and seepage forces. A more mechanistically based detachment model, called the Wilson model, is proposed in this article for modeling the erosion rate of soils using hydraulic analysis of a JET. The general framework of the Wilson model is based on two soil parameters (b 0 and b 1 ). The objectives of this study were to: (1) develop methods of analysis of the JET to determine parameters b 0 and b 1 for the Wilson model in a similar fashion to the previous methodology developed for open-channel flow, and (2) compare the excess stress model parameter (k d ) and the Wilson model parameters (b 0 and b 1 ) determined from the flume tests and JETs for two cohesive soils. Flume tests, treated as the standard test method, and original and “mini” JETs were conducted on two soils to independently measure the excess shear stress model parameter (k d ) and the Wilson model parameters (b 0 and b 1 ). Soil samples of two cohesive soils (silty sand and clayey sand soils) were packed in a soil box for the flume tests and the JETs at water contents ranging from 8.7% to 18.1%. No statistically significant differences were observed for the excess shear stress model parameter (k d ) and for the Wilson model parameters (b 0 and b 1 ) when determined from the flume tests and JET devices, except for b 1 with the original JET. The Wilson model is advantageous in being a more mechanistic, fundamentally based erosion equation as compared to the excess shear stress model. The Wilson model can be used in place of the excess shear stress model with parameters that can be estimated using existing JET techniques.

Application of jet erosion tests (JETs) to study in situ erodibility is gaining popularity. New versions of the JET (original JET versus mini-JET) and new data analysis techniques have introduced questions regarding their operation and data collection procedures. One of the major issues regarding JETs is the high degree of variability of the erodibility parameters (i.e., erodibility coefficient, kd, and critical shear stress, τc). This variability has been attributed to heterogeneity in different soil properties under natural field conditions, but limited research has quantified variability under controlled laboratory conditions, especially for the newer mini-JET. This study uniquely conducted 20 mini-JETs under controlled laboratory conditions on each of two soil types of contrasting texture. Mini-JETs were conducted in situ on streambanks of these same soils in previous research. The laboratory mini-JETs predicted similar values of most parameters with much less variability than in the field. Th...

High streambank erosion and failure rates on streams in the Ozark ecoregion of Oklahoma may be attributed to land use change and degradation of riparian areas. Numerous benefits may be achieved from streambank stabilization, but methods are needed to determine the most critical reaches for investing limited funds. Rapid geomorphic assessments (RGAs) have been used to aid in prioritizing stream reaches. This research (1) applied an existing RGA, the channel sta- bility index (CSI), on several reaches along the Barren Fork Creek and Spavinaw Creek, and (2) modified the existing RGA to create an ecoregion-specific RGA called the Oklahoma Ozark streambank erosion potential index (OSEPI) for larger-order streams in the area. Aerial photography (2003 to 2008) was used to document recent lateral bank retreat for evaluating the RGA scores. Whereas the CSI provided a relatively simple, inexpensive way to identify reaches that should be further evaluated for stability, it failed to disaggregate unstable stream reaches. Limitations included not considering the streambank's cohesion and the difficulty in assessing some metrics. The OSEPI, which included parameters to account for the streambank's cohesion and stream curvature, had higher correlation (R 2 = 0.29 for all reaches; R 2 = 0.45 for reaches with similar soils) with recent streambank erosion. These results indicate promise for its use in prioritizing reach- es for future stabilization projects in the Ozark region of Oklahoma. Additional research is needed to further test the ge- neric and ecoregion-specific RGAs and to determine the conditions that necessitate ecoregion-specific indices.

The erosion rate of cohesive soils is typically computed using an excess shear stress model based on the applied fluvial shear stress. However, no mechanistic approaches are available for incorporating additional forces, such as groundwater seepage into the excess shear stress model parameters. Seepage forces are known to be significant contributors to streambank erosion and failure. The objective of this research was to incorporate seepage forces into a mechanistic fundamental detachment rate model to improve the predictions of the erosion rate of cohesive soils. The new detachment model, which is referred to as the modified Wilson model, was based on two modified dimensional soil parameters (b0 and b1) that included seepage forces due to localized groundwater flow. The proposed model provided a general framework for studying the impact of soil properties, fluid characteristics, and seepage forces on cohesive soil erodibility. Equations were presented for deriving the material parameters from bot...

Typically the erosion rate of cohesive soils is modeled using the excess shear stress equation, which includes two soil parameters: the erodibility coefficient (k d ) and the critical shear stress (I„ c ). Alternatively, a mechanistic detachment rate model (“Wilson Model”) was recently developed to predict the erosion rate of cohesive soils. The general framework of the “Wilson Model” was based on two soil parameters: b 0 and b 1 . The “Wilson Model” is advantageous in being a more mechanistic, fundamentally based erosion equation as compared to the more commonly utilized excess shear stress model. The objective of this research was to derive the excess shear stress model parameters (k d and I„ c ) from field jet erosion tests (JETs) on numerous streambanks across the Illinois River watershed to further investigate the erodibility parameters relative to parameter uniformity, correlations between the derived parameters and soil texture, and the applicability of predictive relationships between k d and I„ c . The second objective was to demonstrate the applicability of the “Wilson Model” using field JET data. If a shift to the more fundamentally based “Wilson Model” is expected, similar investigations into parameter uniformity and correlations are needed. This study also investigated correlations between the excess shear stress model parameters, k d and I„ c , and the “Wilson Model” parameters, b 0 and b 1 . A new miniature version of JET device (“mini” JET) was performed on streambanks of varying soil texture within the Illinois River Watershed in northeastern Oklahoma. Soil samples were acquired at locations of the JETs to measure the particle size distribution, average particle size (d 50 ) and bulk density. When considering correlations between the derived parameters and soil texture, no significant relationships existed between k d or I„ c and bulk density, d 50 , percent clay, silt, or sand, or percent clay-silt. Existing empirical relationships should be used with caution considering the variability between the results observed in this research and previous relationships proposed in the literature. Strong correlations were observed between b 0 and k d (R 2 = 0.90) and between b 1 and I„ c (R 2 = 0.93). Therefore, the Wilson Model parameters closely resemble the empirical excess shear stress parameters, but can be mechanistically defined to account for multiple forces acting during the erosion process.

Fluvial erosion in streambank stability models is typically modeled using an excess shear stress equation based on two soil parameters: the erodibility coefficient (k d ) and critical shear stress (I„ c ). For cohesive soils, methods exist such as jet erosion tests (JETs) for measuring k d and I„ c . For noncohesive bank materials such as sands and gravels, I„ c is commonly estimated using the Shields diagram based on the median particle diameter. However, no universally accepted relationship exists for estimating k d for noncohesive soils. Also, recent research has proposed the use of more fundamentally-based mechanistic detachment models in place of the excess shear stress equation, but limited research has been performed in deriving the parameters of these alternative detachment models. One such model investigated in this research is the Wilson Model, which is based on two parameters: b 0 and b 1 . The objectives of this research included the following: (i) conduct flume experiments on noncohesive gravels to quantify detachment rates relative to the imposed shear stress, (ii) derive k d and I„ c and b 0 and b 1 for these gravels, (iii) determine if relationships can be developed relating k d versus I„ c and b 0 versus b 1 , (iv) compare the k d -I„ c relationship to previously proposed relationships, and (v) compare the relative performance of the models in being able to fit the scour data. Flume experiments were conducted at the USDA-ARS Hydraulics Laboratory. Samples of gravels were extracted from streambanks on the Barren Fork Creek in eastern Oklahoma. The samples were sieved into particle size classes and then at least triplicate flume experiments were performed with average gravel sizes of 0.45, 0.60, 1.30, and 1.90 cm (0.18, 0.25, 0.50, and 0.75 inches, respectively). Scour depth was measured using a point gage during the flume experiment. The k d -I„ c relationships derived from the laboratory experiments followed a power law relationship with the form: k d =2.23I„ c -0.50 (R 2 = 0.65). The Wilson Model parameters b 0 and b 1 derived from this research appeared to have a similar relationship but different magnitude than k d and I„ c . The k d -I„ c or b 0 -b 1 relationships can be used to model fluvial erosion of the noncohesive gravel and therefore the resulting streambank failure of composite banks.

Recent researches were investigated the high concentrations of Lead in Baghdad soils due to the emissions from Leaded fuel of cars, generators, and the industrials. These high concentrations in addition to their impact on human health may impact on the landscape and streambanks and may cause significant issues on soil erodibility. The erosion rate of cohesive soil was usually estimated using two alternative models, excess shear stress model which is depended on two major soil parameters: the critical shear stress, τc, and the erodibility coefficient, kd, and Wilson model which is depended on two mechanistic soil parameters: b0 and b1. A new miniature version of Jet Erosion Test (“mini” JET) was performed to derive both model parameters. The objective of this study was to investigate the influence of Lead pollution on cohesive soil erodibility using “mini” JET under controlled laboratory setups to predict soil erodibility. In order to observe the Lead contamination on soil erodibility, soil samples were mixed with different quantities of Lead concertation and the samples were packed at ASTM standard mold on two different bulk densities. Results show that the Lead pollution increased soil erodibility when the concentration of Lead increased. An inverse relationship between excess shear stress parameters kd and τc was observed as well as between Wilson model parameters b0 and b1. The Wilson model parameters were closely resembled the empirical excess shear stress parameters with benefit that Wilson model parameters are mechanistic parameters.

The trickle irrigation method is a relatively new watering technique which has proven to be a progressive, successful development all over the world. Benefits of using this method in vast areas of Iraq are obvious, especially in parts of drought areas where development and reclamation necessitate the use of trickle irrigation. Previous field research has improved the emission uniformity ( EU ) of trickle irrigation to 100% by individually elevating emitters above the lateral line. In this research, a simpler procedure was proposed for improving EU . This procedure raises the inlet of the lateral pipe to a desired height above ground level. The increasing energy due to elevation drop along the lateral compensates for friction loss, resulting in a more consistent pressure distribution in the pipe. The objective of this research was to improve the resulting EU and to provide a method for determining the optimum inlet height. If tension is placed on the lateral such that its slope is zero at the end of the lateral, its profile becomes a catenary (a hyperbolic cosine function). A hydraulic analysis was performed to estimate flow for each emitter and the resulting EU . Setups that were used in the previous research were simulated. Lateral elevations at the emitters were similar to the elevations of the raised emitters in the previous research, since both approaches were based on the same hydraulic idea. While 100% was not achieved, all EU 's were over 99%. The hydraulic analysis was also used to evaluate the effects of inlet elevation and emitter exponent on EU . It was found that the EU increases when the height of the inlet lateral pipe increases up to a maximum EU , correlating to an optimum design inlet elevation, before it starts to decrease again. Raising the inlet to the optimum elevation caused the EU to increase from 95 to 99.5% compared to leaving the lateral pipe on the ground. The emitter exponent had a negative correlation with the estimated EU , indicating that emitters with lower emitter coefficients may be preferable when designing trickle irrigation systems for maximum EU . The developed procedure for trickle irrigation systems can be used to execute designs of lateral pipe lines that maximize EU .

Seepage influences the erodibility of streambanks, streambeds, dams, and embankments. However, the interaction between fluvial and seepage mechanisms in cohesive soils is still poorly understood. Usually the erosion rate of cohesive soils due to fluvial forces is computed using an excess shear stress equation, dependent on two major soil parameters: the critical shear stress and the erodibility coefficient. A submerged jet test apparatus (JET – Jet Erosion Test) is one method for measuring these parameters. In this study, a new miniature version of the jet test device, referred as the “mini” JET, and a seepage column were utilized to measure the erodibility of cohesive soils influenced by seepage. The experimental setup was intended to mimic a streambed and a streambank when the “mini” JET and seepage column were placed in vertical and horizontal directions, respectively. The horizontal setup involved connecting the jet to the side of the column and imposing a horizontal jet on the soil. Two different soils types, sandy clay loam and sandy loam, were used in the experiments. The soils were packed in three equal lifts in a standard mold at a uniform bulk density (1.4 to 1.7 Mg/m3) at the soils’ optimum water contents. To achieve this optimum water content, the soils were mixed with required quantities of water and allowed to equilibrate for at least 24 hr in a closed container. In order to investigate the influence of seepage forces on erodibility, tests were performed on paired samples prepared in the same way but tested at different times. One sample was tested without seepage using only the “mini” JET. The other sample was tested with seepage forces by including a constant-head in the seepage column. A number of experiments were conducted using various heads and bulk densities. Results show that the erodibility of cohesive soils increased exponentially when seepage forces increased. Even higher erosion rates were observed when inducing erosion with seepage for the horizontal setup, especially at the lower soil bulk densities. The critical shear stress and soil erodibility relationships were obtained for both soils and for all experimental setups.

The importance of groundwater seepage and pipeflow is unknown with respect to other fundamental processes of streambank erosion and failure, although seepage and pipeflow features are observed on streambanks throughout the world that span a range of geomorphologic conditions. Previous field and laboratory research on seepage erosion has demonstrated that groundwater seepage and pipeflow play an important role in the erosion and failure of streambanks. This previous research pointed to seepage forces and undercutting as causes, independent of fluvial forces, of bank failures in some stream systems. Specific seepage and pipeflow mechanisms that cause bank failure may never manifest themselves as transparent features on unstable banks. The objective of this research was to conduct more in-depth laboratory and field experiments to determine how groundwater flow mechanisms, potentially in combination with fluvial processes, affect the occurrence and timing of streambank erosion and failure. Current research activities include conducting three-dimensional soil column experiments to determine the occurrence and prevalence of different seepage erosion mechanisms (i.e., seepage gradient forces and undercutting) across a range of soil textures and cohesions and to identify typical undercut formations when seepage undercutting occurs. Seepage undercuts only formed in sands with a bulk density greater than 1.35 g/cm3 and in loamy sands with a bulk density greater than 1.50 g/cm3. For soils with greater clay content, seepage erosion undercuts may not occur under typical bulk densities. This research also monitored pore-water pressures in a streambank on Dry Creek, a tributary to Little Topashaw Creek located in Chickasaw County, Mississippi, before and during an induced seepage experiment. Seepage flow and erosion rates were measured in four separate experiments on three seeps and demonstrated the capability of seepage to rapidly destabilize streambanks, especially when acting in concert with processes that remove deposited material from the seepage undercut. Usually the erosion rate of cohesive soils from fluvial forces is computed using an excess shear stress equation, dependent on two major soil parameters: the critical shear stress and the erodibility coefficient. A submerged jet test apparatus is one method for measuring these parameters. In this study, a new miniature version of the jet test device and a seepage column were utilized to measure the erodibility of cohesive soils influenced by seepage. Erodibility of cohesive soils exponentially increased with higher seepage gradients. These laboratory and field experiments have further demonstrated the importance of considering seepage mechanisms relative to bank and hillslope stability. Groundwater forces can act over extended periods to destabilize banks between flow events, but specific seepage mechanisms become prevalent under certain streambank stratigraphy and hydrologic conditions.