After the release of the ASCE Manuals and Reports on Engineering Practice (MOP) No. 150: Total Maximum Daily Load Development and Implementation: Models, Methods, and Resources in 2022, the EWRI TMDL Analysis and Modeling Task Committee (TC) continues its work to advance the state-of-the-practice in TMDL development and implementation planning and address emerging issues. The committee is documenting its work in a special collection of papers in the Journal of Environmental Engineering. This paper reports progresses on nine papers addressing various TMDL issues/topics: (1) watershed models to predict climate change impacts, (2) advanced surface water quality modeling, (3) integration of the climate assessment modules in TMDL models, (4) advances in watershed and receiving water models for simulating PFAS, (5) advances in modeling best management practices and green infrastructure for TMDL implementation planning, (6) harmful algae bloom predictive approaches, (7) incorporation of social aspects and stakeholder participations in TMDL modeling, (8) overcoming data scarcity, and (9) survey of TMDL community. All the papers except #6 have been authored by the TC members. Paper 6, an external paper submitted and accepted in the collection, replaces the committee paper on the topic as it overlaps and meets the committee objectives. The committee has plans to write more papers and summarize all in a book to be a guidance document supplementing the ASCE MOP 150.

In this paper, a review of advances in total maximum daily load (TMDL) implementation planning by modeling best management practices (BMPs) and green infrastructure (GI) practices along with enhanced (hybrid/streamlining) approaches is presented. The review emanates from Chapter 12 of the recent ASCE Manual of Practice on TMDLs. The latest models and modeling tools, specifically the United States Environmental Protection Agency's (USEPA's) GI Modeling Toolkit and the Landscape and Green Infrastructure Design (L-GrlD) model for formulating GI strategies with flexibility to support stakeholder engagement, are reviewed. In addition, other decision support tools that can help advance the state-of-the-practice of TMDL implementation are included in the synthesis. Advances in incorporating model uncertainties related to BMPs and GI practices in TMDL analysis are briefly discussed. Furthermore, enhanced approaches to cost-effective TMDL implementation measures are discussed, which can be combined with other watershed management strategies for greater synergy between TMDL modelers and other watershed stakeholders. Some emerging technologies such as remote sensing can be useful for monitoring the effectiveness of the TMDL implementation measures over time. Several emerging technologies are discussed through an example illustrating the long-term efficacy of implementation practices. Finally, an enhanced approach to the full TMDL life cycle that explicitly incorporates BMPs and GI practices in the TMDL is proposed, and expected benefits of this approach are demonstrated with conceptual diagrams.

This paper presents a communications framework to overcome the connectivity constraints due to the nonavailability of the line-of-sight transmissions in indoor optical communication systems. This nonavailability can arise for various reasons, such as blockages due to physical objects, unfavorable device orientations or large distances between the transmitter and the receiving devices. The proposed system utilizes multiple intelligent reflecting surface (IRS) arrays and device-to-device (D2D) communications. The D2D communication is realized using infrared (IR) light-emitting diodes (LEDs) with limited output power for eye safety. The performance of this system depends significantly on the assignment of the mirrors in the IRS arrays to the appropriate user links and a direct combinatorial assignment search is too complex to implement. The proposed approach identifies the assignment of each mirror in the IRS arrays as a multi-armed bandit (MAB) problem, and the assignment of all the mirrors together as a combinatorial MAB (CMAB) problem. Since a simultaneous movement of all the IRS mirrors during the implementation of the CMAB algorithm could cause frequent link disruptions, a CMAB algorithm with low disruptions (CMAB-LD) is proposed to obtain the best mirror assignment with low link disruptions. Simulation results demonstrate that the proposed algorithm can provide significant improvement in reward performance and the total reward increases by more than 100% over random mirror assignments when the channels are blocked with high probabilities. In small size problems, the proposed CMAB-LD is found to achieve the global optimal solution in just a few rounds of full arm explore operations.

Fourteen leading watershed models simulating hydrology, erosion, and transport/fate of sediment and pollutants were critically reviewed by the EWRI Total Maximum Daily Load (TMDL) Analysis and Modeling Task Committee. The review was published in Chapter 2 of the ASCE Manual of Practice (MOP) 150 "TMDL Development and Implementation—Models, Methods, and Resources," to provide guidance in selecting models. To further advance watershed modeling, this paper has looked into some critical aspects of watershed models, specifically, spatial discretization such as lumped, semi-distributed, or fully distributed; temporal resolution in preserving the most dynamics of the physical processes; simulating best management practices; computing probability and confidence level of model outputs; incorporating computational efficient numerical solutions; and simulating constitutes of emerging concerns such as PCB and PFAS. The applicability of the models beyond TMDL, such as holistic watershed management including the consideration of climate change impacts, is discussed in the context of advancing successful and comprehensive watershed modeling.

The ASCE Manual of Practice (MOP) 150, "Total Maximum Daily Load (TMDL) Development and Implementation: Models, Methods, and Resources," was written by the ASCE-EWRI TMDL Analysis and Modeling Task Committee. Chapter 12 of the MOP, "Modeling for Total Maximum Daily Load Implementation," discusses state-of-the-practice on uses of models in TMDL implementation planning. The committee is currently expanding its work. In this paper, an overview of green infrastructure (GI) and modeling of those for TMDL implementation and reviews of specific models, including the USEPA's GI Modeling Toolkit and the Landscape and Green Infrastructure Design (L-GrlD) model for designing GI strategies with flexibility to support stakeholder engagement and decision support tools for stormwater management that can advance the TMDL implementation state-of-the-practice, are presented. Non-traditional approaches are presented with cost-effective implementation while broadening the scope of TMDL to combine with other similar watershed management efforts for greater synergy. Designing of TMDL implementation measures (e.g., BMPs), including engaging stakeholders and managing multiple co-benefits and diverse costs, is discussed as those are crucial steps for the success of TMDLs. Emerging technologies, for example, remote sensing, are discussed with an example from the perspective of efficacy of the implementation measures in the long run.

This paper highlights the flood and bank erosion problems of the complex Brahmaputra River system, which flows through parts of three countries (China, India, and Bangladesh) covering a distance of 2,880 km with a focus on erosion of its banks and taking away valuable lands of the Majuli Island in Assam, India. The Core Professional Group for the Brahmaputra (CPGB), a non-government organization (NGO) formed in 2010 by a group of experienced international river management professionals, took an initiative to review the chronic flood and river bank erosion that has occurred in Assam, and the control measures adopted by the authorities during the last six decades. CPGB identified possible mitigation of flooding and erosion of the Majuli Island as a pilot project. CPGB has submitted several proposals of the pilot project to the Government of India. Tasks from the proposals, including data gathering, geology and geomorphological study, mathematical modelling of river hydraulics and sediment transport, and sustainable design solutions, are described in the paper. The paper is to be construed as a technical exchange forum between CPGB and river engineering experts at an independent session on the Brahmaputra River in the EWRI Congress, 2022.

Physically Unclonable Functions (PUFs) are emerging hardware security primitives that leverage stochastic random process variations during chip manufacturing to generate unique secrets. However, the biased systematic variations that exist in the process variations will cause non-random spatial correlations among PUF elements in the layout, which significantly degrades randomness of PUF generated secrets. Existing methods of reducing systematic variations involve operations with high computational complexity and therefore require high implementation overheads. In this paper, we propose a lightweight method based on averaging neighboring PUF values to derive spatial bias and hence reduce spatial variations. Experimental results using RO PUF data from 192 Spartan 3E FPGAs show that the proposed method achieves comparable or even better randomness improvement compared to existing methods. The proposed method also demonstrates advantages of parameter diversity. The proposed method implemented on Xilinx FPGAs shows up to more than 10x lower implementation overhead compared with the existing method.

This paper presents a channel analysis method for single and double scattering events in non-line-of-sight (NLOS) ultraviolet (UV) communication systems. In general, the calculations of path loss and impulse response of such systems require Monte Carlo random number generations. However, the high computational costs of Monte Carlo methods impose severe limitations on quick reliable evaluations of system performance under complex atmospheric conditions. This paper proposes a sample-based UV channel characterization approach that improves computational performance by multiple orders of magnitude. The proposed novel approach uses fixed probability-based sampling. The method focuses only on single and double scattering events which dominate the received signal. The effects of various fog and dust aerosols are discussed under non-planar realistic conditions. The results demonstrate reliable channel characterization with significantly lower complexity using the proposed approach.

This letter investigates the physical layer security of the data from the weak user (WU) against interception by the strong user (SU) in non-orthogonal multiple access (NOMA) systems. The proposed NOMA using directional modulation (NOMAD) allows access of the intended symbols at the WU while giving access to a different but valid lower order symbol alphabet to the SU for performing successive interference cancellation. The optimal lower order symbol alphabet and directional modulation vectors are designed in a multiple-input single-output framework. The sum and secrecy rate results show that NOMAD provides non-zero secrecy rates against the zero secrecy rate of NOMA and also delivers spectral efficiency benefit of NOMA. Further, NOMAD performs better than an orthogonal multiple access, such as a zero-forcing beamformer. A combined NOMA/NOMAD can present trade-offs between sum and secrecy rates. Bit error results are also presented confirming the advantages of the proposed NOMAD.

Dealing with flooding, upland soil and streambank erosion, sedimentation, and contamination of water from agricultural, rural, and urban watersheds, and understanding the underlying natural processes are continued challenges to the environmental hydraulics field and in the management of sustainable water and environmental resources around the world. Watershed simulation models are useful tools to understand and analyze the processes and the problems and help mitigate those through evaluating the effects of land-use changes and best management practices. Developing adequate watershed simulation models and verifying those on real world watersheds with measured and monitored data are challenging. A Dynamic Watershed Simulation Model (DWSM) is being developed at the Illinois State Water Survey to simulate surface and subsurface storm water runoff, propagation of flood waves, soil erosion, and transport of sediment and agricultural chemicals in agricultural and rural watersheds. Different components of the DWSM have been applied to watersheds in Illinois for testing these components and assisting local watershed planning groups in planning restoration projects. Some of the recent progresses made in this ongoing modeling study are presented here. The soil erosion and sediment transport component was tested (calibrated and verified) on the Big Ditch watershed in Illinois, a 100-square-kilometer tributary subwatershed of the Upper Sangamon River basin draining into Lake Decatur. Two different divisions of the watershed, one with coarse subdivisions and the other with fine subdivisions were used in the simulations to investigate scaling effects on the parameter values and the model results.

We present a novel single-camera 3-D spatial localization method using optical triangulation with temporaldifference image processing. The proposed system uses a blinking LED circle attached to the target as a marker. The background image except the marker circle is removed by applying temporal difference of the images since the imager samples at twice of the target blinking frequency. The 3-D spatial location can be calculated using simple equations to save computing energy without computing triangulation functions. The proposed method can be applied in low-power outdoor unmanned aerial vehicle (UAV) localization applications. The experimental results show that the proposed method can measure an object with an error of 0.4 m in the range of 30 m, or 0.1 m in the range of 3 m. The proposed method provides an attractive low power solution for remote UAV alignment and control.

The EWRI Total Maximum Daily Load (TMDL) Analysis and Modeling Task Committee (TMDL TC) under the Watershed Management Technical Committee (WMTC) of the Watershed Council was formed to address concerns over the current practices of analysis and modeling in TMDL development and implementation in terms of analysis technique and model selection, data requirement, calibration, validation, and uncertainty reporting. The committee reviewed the current practices of analysis and modeling in TMDL development and implementation and documented in a report “Total Maximum Daily Load Analysis and Modeling: Assessment of the Practice” published by ASCE: http://ascelibrary.org/doi/book/10.1061/9780784414712

This paper reviews 14 prevalent watershed models for their capabilities, credibility, and suitability in total maximum daily load (TMDL) development and implementation. Brief descriptions of the models, including sources, capabilities, and applicability are presented. General information such as intended watershed and simulation types, simulated outputs, uncertainty analysis capabilities, graphical user interface, and availability are also presented. Mathematical bases of the hydrologic and water quality simulations, which indicate credibility, expected performance, and accuracy, and dictate model features (e.g.,structure, input data, and parameters) are presented. Routing procedures, the backbones of the models, are compared and ranked. The Gridded Surface and Subsurface Hydrologic Analysis (GSSHA) and MIKE SHE (Systeme Hydrologique Europeen) models rank high on overland and Storm Water Management Model (SWMM) on channel/pipe flow routing as the most accurate for representation of the physical processes and also the most numerically complex. The Generalized Watershed Loading Function (GWLF) and Spreadsheet Tool for the Estimation of Pollutant Load (STEPL) rank at the bottom on both the aspects. The rest of the models are in between, although the Dynamic Watershed Simulation Model (DWSM) is computationally efficient among kinematic wave models. Notable strengths and limitations of the models for TMDL development and implementation are presented. All these provide valuable information on the models, not readily available in a concise form elsewhere, to compare and help determine relative credibility and make informed selections for TMDLs and similar studies. Future research should focus on further comparisons of the models based on other key aspects such as simulation capabilities of processes, uncertainty analysis, required resources, and performances on watersheds followed by developing better models or improving existing ones by strengthening the weaknesses found. Robust physically based algorithms, uncertainty analysis capabilities, and use of remotely sensed and high-resolution data are recommended to be part of the model improvements.

A novel 3-D spatial localization method using a single camera with temporal-difference image processing is proposed. The proposed active localization method uses a ring of light-emitting diodes embedded on the target. The diameter and the central location of the ring's image on the image sensor are used to estimate the target location using a Volterra series expansion of the target coordinates. No knowledge of the camera hardware parameters is needed. Instead, Volterra series parameters are obtained through a prior training that needs to be performed only once. The proposed method can be implemented with low computational complexity and storage. The performance of the proposed method is compared against an earlier method that relies on prior knowledge of the camera hardware parameters. The proposed method demonstrates excellent performance even when the target is located far away from the axial direction of the camera lens. The proposed method can be applied in low-power outdoor unmanned aerial vehicle localization and indoor robotic navigation.

This letter presents an iterative combinatorial symbol design algorithm for the generalized spatial modulation (GSM) in visible light communication systems. An approach that is fundamentally different from the available low complexity design methods is adopted by jointly considering both spatial and intensity bits in the symbol design. The proposed method is compared against existing symbol design methods for both photodiode array and camera receivers in terms of error performance and implementation complexity. The algorithm is shown to outperform several GSM symbol design methods, providing many decibels of performance gain. The proposed algorithm is also applicable to generalized space-shift keying and spatial modulation.

A joint optimization algorithm for designing multi-beam directional modulation (MBDM) symbols with artificial noise (AN) is proposed for physical layer security in wireless communication systems. The proposed approach guarantees specific minimum error probabilities along the given eavesdropper directions. The algorithm is implemented by iterating between a convex program that optimizes symbols with AN and a convex (linear) program optimizing a set of weight vectors to guarantee specific error probabilities along the eavesdropper directions. The proposed method is compared against several MBDM algorithms, and is found to provide excellent bit error rate performance results. A hardware experimental test bed is described and is used to demonstrate the feasibility of the proposed solution.

This paper investigates optimal symbol set selection for the generalized spatial modulation (GSM) in visible light communication (VLC) systems. Realizing that the optimal search involves a highly complex combinatorial problem, a symbol set generation tree is proposed. The tree allows assessment of the system performance at each node and can be terminated early to obtain near-optimal solutions with reduced complexity. It is observed that the proposed optimal symbol search provides performance improvement of many dBs over results obtained with averaged random sets. The benefit of the optimized symbol set design is found to increase with increasing number of pulse amplitude modulation levels. Our contributions also include integration of possible rotations of the array in the mathematical model, and the demonstration of the results to be robust to channel changes due to rotations and shifting of the array in the image plane. Finally, the results are validated through hardware experimental results.

Estimation of the image location of a mobile LED array transmitter on the camera sensor plane of a digital camera is considered. A Bayesian framework is used to design an initial large measurement matrix over multiple image frames to exploit inter-frame temporal correlations. This large matrix is then factorized into two component matrices; one is used as the front-end measurement matrix with the potential for hardware implementation while the other is designed for software implementation. The factorization can be performed offline through fixed point iterations. The proposed measurement matrix design directly exploits possible transmitter mobility through a parametric framework. The findings are validated through analysis, computer simulation and hardware experiments. Sub-pixel localization accuracy with significant compression is achieved, and the proposed compressive parameter estimation outperforms results obtained using a Gaussian measurement matrix.