Pressure Relief Wells: Analysis of Subsurface Heterogeneity to evaluate Relief Well Locations for Mississippi River Levees

“When designing pressure relief well systems, it is imperative to understand what major geomorphology and heterogenies features are present, such as buried oxbow lakes, especially when the feature is parallel to the source, such as the Mississippi River. When present, there is a notable greater increase in head pressures, especially on the landward tow of the levee. This can cause erosional features that originally thought of to have been protected from by installing pressure relief wells. When comparing the effective hydraulic conductivities of horizontal clay layers and vertical clay layers spanning the length of the model, little to no noticeable difference can be discerned, also long as the clay volume is under 30%”--Abstract, page iii

Investigation of Groundwater Depletion and Leveel Underseepage with Unstructured-Grid Modeling Approach

Unstructured grid is a tessellation of geometric shapes in irregular patterns that provides flexibility in grid design for groundwater modeling. However, groundwater modeling is mostly developed with uniform grid tessellation and layer, which could simplify model structure or cause expensive computational costs in high-resolution simulations. Unstructured grid incorporates non-uniform horizontal and non-uniform vertical discretizations providing the capability to replicate complex hydrostratigraphy, capture geologic features that are crucial for groundwater flow simulation, and reduce computational costs while maintaining a high resolution for areas of interest. This study contains three parts to investigate unstructured-grid approach on constructing high-fidelity groundwater models, comparisons with analytical relief well evaluation, and optimization implementation on relief well operations. The first study develops a three-dimensional (3-D) groundwater model using MODFLOW-USG on an unstructured grid to evaluate relief well performance at the Profit Island vicinity levee and conduct comparative analysis with conventional seepage analysis (i.e., blanket theory). Consequently, this case study indicates that 3-D modeling is a more accountable and precise tool than blanket theory. The second study proposes relief well operations optimization as an alternative to increase levee and floodwall factor of safety against underseepage, which is achieved by a multi-objective mixed-integer non-linear programming implemented with a 3-D unstructured groundwater model. The approach is demonstrated at the Inner Harbor Navigation Canal, New Orleans, Louisiana. Relief well operations optimization provides decision-makers useful tradeoffs between averaged factor of safety deficit, total pumping rate, and the number of pumping wells for making pumping decisions. The third study advances unstructured grid to develop a high-fidelity 3-D groundwater model using a lithology model for the Louisiana Capital Area Groundwater Conservation District (District) on the Southern Hills Aquifer System. Groundwater flow simulation, water budget analysis, uncertainty analysis, and comparisons with satellite data provide comprehensive understanding of groundwater storage variation in the District and evaluate groundwater depletion induced by excessive prolonged groundwater withdrawals in the Baton Rouge area. This study successfully demonstrates the capability of unstructured-grid approach on groundwater modeling to simulate groundwater dynamics within complex subsurface hydrogeological structures, evaluate relief well performances, and optimization implementation

Solutions Network Formulation Report. The Potential Contribution of the Landsat Data Continuity Mission to the Mississippi Coastal Improvements Project

The 2005 hurricane season - especially Hurricane Katrina - left the Mississippi Gulf Coast devastated. In its efforts to assist in coastal re-building efforts, the U.S. Congress passed the Defense Appropriation Act of 2006. This legislation directed the Secretary of the Army, via the USACE, to generate reports discussing possible projects that would improve the State of Mississippi?s coastal region. These projects are referred to as the MsCIP. Data collected via the LDCM OLI could be used to evaluate the success of projects that result from the MsCIP by monitoring regional coastal changes associated with such projects. This Candidate Solution is in alignment with the Coastal Management, Water Management, and Disaster Management National Applications and will benefit society by improving the post-Hurricane Katrina Mississippi Gulf Coast

Assessing the Risk of 100-year Freshwater Floods in the Lamprey River Watershed of New Hampshire Resulting from Changes in Climate and Land Use

What is the coastal resource issue the project sought to address? Both the magnitude and frequency of freshwater flooding is on the rise in seacoast NH and around much of New England. In the Great Bay watershed, this is the result of two primary causes: 1) increases in impervious surface stemming from a three-to-four fold increase in developed land since 1962; and 2) changing rainfall patterns in part exemplified by a doubling in the frequency of extreme weather events that drop more than 4 inches of precipitation in less than 48 hours (Wake et al., 2011) over the same time period. Moreover, the size of the 100-year precipitation event in this region has increased 26% from 6.3 inches to 8.5 inches from the mid 1950’s to 2010 (NRCC and NRCS, 2012). One consequence is the occurrence of three 100-year floods measured on the Lamprey River at Packers Falls since 1987, and a fourth if the three days of flooding in March of 2010 had occurred instead in two days (Figure 1). Flooding events are expected to continue to increase in magnitude and frequency as land in the watershed is further developed and climate continues to change in response to anthropogenic forcing (e.g., Hayhoe et el., 2007; IPCC, 2007; Karl et al., 2009). Land use management strategies, in particular low impact development (LID) zoning requirements, are one strategy that communities can employ for increased resiliency to flooding with the greatest influence in urban environments

Assessing the Risk of 100-year Freshwater Floods in the Lamprey River Watershed of New Hampshire Resulting from Changes in Climate and Land Use

What is the coastal resource issue the project sought to address? Both the magnitude and frequency of freshwater flooding is on the rise in seacoast NH and around much of New England. In the Great Bay watershed, this is the result of two primary causes: 1) increases in impervious surface stemming from a three-to-four fold increase in developed land since 1962; and 2) changing rainfall patterns in part exemplified by a doubling in the frequency of extreme weather events that drop more than 4 inches of precipitation in less than 48 hours (Wake et al., 2011) over the same time period. Moreover, the size of the 100-year precipitation event in this region has increased 26% from 6.3 inches to 8.5 inches from the mid 1950’s to 2010 (NRCC and NRCS, 2012). One consequence is the occurrence of three 100-year floods measured on the Lamprey River at Packers Falls since 1987, and a fourth if the three days of flooding in March of 2010 had occurred instead in two days (Figure 1). Flooding events are expected to continue to increase in magnitude and frequency as land in the watershed is further developed and climate continues to change in response to anthropogenic forcing (e.g., Hayhoe et el., 2007; IPCC, 2007; Karl et al., 2009). Land use management strategies, in particular low impact development (LID) zoning requirements, are one strategy that communities can employ for increased resiliency to flooding with the greatest influence in urban environments

Analisis Pengaruh Bangunan Groundsill 5 Dan 6 Terhadap Perubahan Dasar Sungai Cipamingkis Di Kabupaten Bogor

Sungai Cipamingkis mengalami degradasi yang cukup parah kurang lebih sepanjang 10 km, mulai dari Bendung Cipamingkis sampai dengan Jembatan Cibarusah. Salah satu akibatnya, terjadi keruntuhan Jembatan Jonggol-Cariu pada ruas sungai tersebut. Upaya penanganan yang dilakukan adalah dengan membangun Groundsill 5 dan Groundsill 6. Penelitian ini dilakukan untuk mengetahui pengaruh bangunan Groundsill 5 dan Groundsill 6 terhadap perubahan dasar Sungai Cipamingkis di sekitar Jembatan Jonggol-Cariu menggunakan HEC-RAS 2D. Simulasi pemodelan dilakukan dengan debit banjir rencana periode ulang 2 dan 100 tahun. Persamaan angkutan sedimen potensial yang digunakan adalah MPM-Toffaletti. Analisis model numerik dibagi menjadi 8 skenario pemodelan. Hasil analisis menunjukkan ruas Sungai Cipamingkis dari hulu Jembatan Jonggol-Cariu sampai dengan hilir Groundsill 6 berpotensi mengalami degradasi dasar sungai maksimum mencapai 3,3 m dan pada lokasi sekitar Jembatan Jonggol-Cariu mencapai 2,8 m. Bangunan Groundsill 5 dan Groundsill 6 dapat mengurangi potensi degradasi di sekitar Jembatan Jonggol-Cariu menjadi 0,24 m atau berkurang sebesar 91,1%. Tetapi di hilir bangunan Groundsill 6 potensi degradasi masih cukup tinggi sehingga masih diperlukan upaya penanganan degradasi di hilirnya untuk mengendalikan degradasi Sungai Cipamingkis secara keseluruhan