Development of A Comprehensive Model for Erosion and Sediment Control towards Good Water Governance: UKM Campus as A Watershed Model

This study was carried out to develop a whole ecosystem-based erosion and sediment transport control management system of UKM Campus Watershed which is a sub-basin of Langat River Basin catchment. This is done through the development of an Erosion and Sediment Control (ESC) model for the UKM campus watershed that includes localised technology, information and communication system, as well as awareness and community participation for the greening and rehabilitation of UKM Campus. The management system was developed to give a strong participatory element and to ensure that the model will be placed into a user friendly context to make data input and model operation simple for stakeholders with limited resources and training in the use of the models. The application of hydromulching (bioengineering technology) is adopted as part of the ESC study by using the local components to recover most landslides occurred in UKM Campus. It is also as an option where the post-landslide restoration works involving conventional civil designs are costly and sometimes not practical at remote sites. Therefore (due to cost constraints), the remoteness of the sites and low risk to lives and property, bioengineering was the option taken for erosion control, slope stabilization and vegetation establishment.

Soil erosion prediction using USLE model in Cangkringan micro watershed model, Yogyakarta

Land use that is not in accordance with ecological principles causes’ excessive soil erosion. Soil erosion has an impact on decreasing soil productivity, increasing critical land and causing land degradation. It is essential to predict the amount of soil lost due to soil erosion to determine the conservation efforts applied to suppress the erosion rate. The estimation of erosion in this study using the USLE model, using 5 factors, namely erosivity (R), erodibility (K), slope length (LS), crop management (C), and soil conservation (P). The results showed that the level of erosion hazard in Cangkringan Micro Watershed Model consisted of 5, namely very light covering an area of 29.14 ha (2.15%), mild covering an area of 642.31 ha (47.44%), moderate covering an area of 545.62 ha (40.30%), heavy area of 129.00 ha (9.53%) and very heavy area of 7.94 ha (0.58%).

Evaluation of Ecosystem-Based Adaptation Measures for Sediment Yield in a Tropical Watershed in Thailand

Ecosystem-based adaptation (EbA) can potentially mitigate watershed degradation problems. In this study, various EbA measures were evaluated using a bio-physical model called the Soil and Water Assessment Tool (SWAT), in a small, forested watershed named Hui Ta Poe, in the northeastern region of Thailand. The developed watershed model was first used to investigate the effect of various degraded watersheds due to land-use changes on the sediment yield in the study area. The most degraded watershed produced an annual average sediment yield of 13.5 tons/ha. This degraded watershed was then used to evaluate the effectiveness of various EbA measures such as reforestation, contouring, filter strips, and grassed waterways in reducing the sediment yield. Under all individual and combined EbA scenarios analyzed, there was a significant reduction in sediment yield; however, the maximum reduction of 88% was achieved with a combined scenario of reforestation, grassed waterways, and filter strips. Reforestation alone was found to be the second-best option, which could reduce the sediment yield by 84%. Contouring alone was the least effective, with a reduction in sediment yield of only 23%. This study demonstrates the usefulness of implementing EbA measures for sediment management strategies to address watershed degradation, which is a severe problem across the globe.

Event Based Post-Fire Hydrological Modeling of the Upper Arroyo Seco Watershed in Southern California

Understanding, development and integration of pre-fire and post-fire watershed hydrological processes into a watershed hydrological model in a wild-fire repeating region similar to parts of California is critical for emergency assessments. 95% of the upper Arroyo Seco watershed located in Los Angeles County in southern California was burned by the Station fire that occurred in August 2009, significantly increasing the watershed observed runoff. This watershed was employed to develop the January 2008 rainfall runoff model as a pre-fire event-based watershed hydrological model. This pre-fire watershed model was subsequently employed in the rainfall events of 18 January 2010 and 27 February 2010, a few months after the fire event of August 2009. The pre-fire watershed model when employed in the post-fire rainfall events without considering the fire effects vastly underestimated the simulated discharge. For this reason, in this study of the post-fire catchment runoff modeling the following points are taken into consideration: (a) a realistic distributed initial soil moisture condition; (b) a formulation that includes a reduction factor and a burn severity factor, as multiplying factors to soil hydraulic conductivity in the soil characteristic curve; and (c) runoff routing parameterization under burned conditions. Developing the post-fire Arroyo Seco watershed model by using the above-mentioned points enhanced the Nash–Sutcliffe Efficiency from −24% to 82% for the 18 January 2010 rainfall event and from −47% to 96% for the 27 February 2010 rainfall event.

Evaluation of Water Circulation by Modeling: An Example of Nonpoint Source Management in the Yeongsan River Watershed

Owing to urbanization, impervious areas within watersheds have continuously increased, distorting healthy water circulation systems by reducing soil infiltration and base flow; moreover, increases in surface runoff deteriorate water quality by increasing the inflow of nonpoint sources. In this study, we constructed a Hydrological Simulation Program—Fortran (HSPF) watershed model that applies the impervious area and can set medium- and long-term water circulation management goals for watershed sub-areas. The model was tested using a case study from the Yeongsan River watershed, Korea. The results show that impervious land-cover accounts for 18.47% of the upstream reach in which Gwangju City is located; approximately twice the average for the whole watershed. Depending on the impervious area reduction scenario, direct runoff and nonpoint source load could be reduced by up to 56% and 35%, respectively; the water circulation rate could be improved by up to 16%. Selecting management goals requires the consideration of both policy objectives and budget. For urban areas with large impervious cover, the designation of nonpoint source management areas is required. For new cities, it is necessary to introduce water circulation systems (e.g., low impact development techniques) to improve rainwater penetration and recharge and activate preemptive water circulation.