Under its civil works program, the U.S. Army Corps of Engineers (Corps) plans, builds, operates, and maintains a wide range of water resource facilities. The Corps also undertakes flood-fighting activities and other natural disaster response activities. These emergency activities have been authorized by Congress and generally have been funded by supplemental appropriations, which have been significant relative to Corps discretionary appropriations since 2005. From 1987 to 2016, Congress has appropriated approximately $33.2 billion in Corps supplemental appropriations. Of this total, Congress provided $31.4 billion from 2005 to 2016, which was significant relative to the agency's regular (i.e., nonsupplemental) annual discretionary appropriations over that period (approximately $63.8 billion for FY2005 through FY2016). If supplemental bills provide funds to the Corps, they most frequently fund two accounts: Flood Control and Coastal Emergencies (FCCE; i.e., flood fighting, repairs to damaged nonfederal flood-control projects) and Operations and Maintenance (O&M; i.e., repairs to existing Corps projects). In some instances, principally since 2005, Congress also has provided supplemental funding for other Corps accounts, such as the Mississippi River and Tributaries (MR&T) account and the Construction account. Of the supplemental funds that Congress provided to the Corps for Hurricanes Katrina and Sandy, 31% and 66%, respectively, were for construction activities. Congress also provided the agency with $4.6 billion as part of the American Recovery and Reinvestment Act of 2009 (ARRA; P.L. 111-5 ). In the wake of major flooding and other natural disasters, Congress often considers whether to provide supplemental appropriations to the Corps and other agencies. Proponents of providing supplemental funding for the Corps argue that these investments are significant for recovery efforts and improve flood resilience of the affected areas. Congress may provide these funds with special considerations (e.g., designated as emergency funding and not requiring budgetary offsets; waiving nonfederal cost-share requirements). Others argue that the annual appropriations process is the more appropriate forum for deciding on significant federal flood-damage reduction investments, contending that postdisaster investments should be subject to the same project-development and cost-sharing requirements as other similar Corps projects and should compete in the agency's annual budget-development process. Other stakeholders would prefer more attention and funding that supports other programs and measures to reduce the nation's flood risks. (For an overview of federal flood-related assistance programs, see CRS Report R45017, Flood-Risk Reduction and Resilience: Federal Assistance and Programs , by [author name scrubbed] et al.) This report analyzes Corps supplemental funding. The report focuses on supplemental funding provided directly to the Corps from 1987 to 2016, as well as recently proposed supplemental funding in H.R. 4667 —Further Additional Supplemental Appropriations for Disaster Relief Requirements, 2017 (as passed by the House). The report does not include extensive analysis of annual Corps discretionary appropriations or supplemental appropriations for other agencies. Apart from Corps disaster response, the Federal Emergency Management Agency (FEMA) has extensive authority to assist and coordinate disaster response actions under the National Response Framework, and FEMA receives significant regular and supplemental appropriations for this work. Although the Corps performs work under some mission assignments for FEMA (i.e., funded by FEMA, under direction of the President and FEMA), that work is not addressed in this report. The majority of natural disaster-related supplemental appropriations generally are placed into one of the following four Corps budget accounts based on the type of activity funded. The FCCE account is the primary account through which the Corps funds disaster-related activities. The primary activities funded under FCCE are flood fighting (e.g., sandbagging), emergency preparedness and response, and repair of damaged nonfederal flood and hurricane protection projects. Congress authorized the Corps in the Flood Control Act of 1941 (33 U.S.C. §701n) to assist in flood fighting and flood response. The Corps can assist in flood fighting at the discretion of its Chief of Engineers to protect life and property, principally when state resources are overwhelmed. Congress also authorized the Corps to operate the Rehabilitation and Inspection Program (RIP, also known as the P.L. 84-99 program) to fund the repair of participating nonfederal flood-control works (e.g., levees, dams, dunes) damaged by natural events. Repairs under this program are funded by the agency's FCCE account. Congress also has directed the Corps to use supplemental funds to repair and rebuild federally owned flood-control and other projects (e.g., navigation projects) through the agency's O&M and Construction accounts. In the event of an emergency, Congress has given the Secretary of the Army (generally delegated to the Assistant Secretary of the Army [Civil Works]) discretion to transfer from existing appropriations the monies necessary for the emergency work referenced above, until funds become available in the applicable account through supplemental appropriations or other avenues. In recent floods, the Corps has exercised this authority to transfer regular annual appropriations from ongoing projects (i.e., projects funded by annual appropriations) to pay for emergency actions. The Corps has then internally reimbursed itself for this funding once supplemental appropriations have become available. The O&M account funds activities related to existing Corps projects, including upkeep of physical infrastructure and other activities (i.e., dredging of ports and waterways). Common disaster activities funded under this account include repair of damaged federally operated flood and hurricane protection projects (e.g., dams, levees, floodwalls) and dredging of authorized federal navigation channels. The MR&T account consists of flood-control and navigation projects for the lower Mississippi River Valley. Supplemental expenditures under this account consist primarily of repair to damaged MR&T levees, floodways, and other project features. The Construction account funds new project construction and major upgrades to existing projects (e.g., significant dam repairs). Supplemental construction funding has been used at times to improve existing Corps coastal and riverine flood-risk reduction projects and for new Corps construction projects to reduce flood risks. Congress previously has provided the Corps with approximately $33.2 billion (nominal dollars) in supplemental funding in 26 laws enacted between 1987 and 2016. It is considering legislation, principally H.R. 4667 , that would provide the Corps an additional $12.09 billion in supplemental appropriations for the agency's activities associated with response, repair, and recovery from natural disasters including Hurricanes Harvey, Irma, and Maria in 2017. This section discusses enacted Corps supplemental appropriations, as well as Corps supplemental funding proposed in H.R. 4667 in the 115 th Congress. It also discusses common issues that policymakers consider in deliberating on these supplemental appropriations bills. Table 1 shows account-level funding in enacted Corps supplemental appropriations bills and in H.R. 4667 . Of the $33.2 billion in enacted supplemental appropriations legislation, most of this amount ($31.4 billion) was provided in 12 appropriations laws enacted between 2005 and 2016. Adjusting prior-year appropriations for inflation, Congress provided the Corps with approximately $38 billion (in 2016 dollars) in supplemental appropriations between 1987 and 2016. Of this total, 92% was provided between 2006 and 2016. Enacted Corps supplemental appropriations and H.R. 4667 also are shown by year in Figure 1 . The discussion below differentiates between five primary types of supplemental funding that the Corps received or the 115 th Congress is considering: funding for the 2005 hurricanes; funding for Hurricane Sandy response and recovery; funding for "all other" floods, hurricanes, and other natural disasters; funding for other nondisaster purposes, such as economic recovery and facility security; and funding proposed in H.R. 4667 (as passed by the House) for natural disasters including Hurricanes Harvey, Irma, and Maria. Separately, the Appendix lists the disaster events that were explicitly referenced in enacted Corps supplemental appropriations from 2003 to 2016 and in H.R. 4667 . As noted above, the 2005 hurricanes (primarily Hurricane Katrina) account for much of Corps supplemental appropriations since 2003. The $16 billion received for these storms is more than three times the size of the agency's annual civil works budget. These appropriations were provided in six separate supplemental appropriations bills passed between 2005 and 2009, and most of these funds were designated for rebuilding and in some cases significantly strengthening Corps facilities, principally in Southeast Louisiana. Approximately 94% of the supplemental funds appropriated for Corps hurricane response and recovery went to activities in Louisiana, including $14.5 billion for protective measures in Southeast Louisiana. These funds were used for significant repair and strengthening of 350 miles of levees and floodwalls in New Orleans and new surge-protection barriers, including the Inner Harbor Navigation Canal Surge Barrier, which is one of the largest surge barriers in the world. Although the federal government funded 100% of the costs of FCCE and O&M infrastructure in Southeast Louisiana, most of the supplemental funds for construction projects were subject to federal-nonfederal cost-sharing requirements (generally a 65/35 federal/nonfederal split). That is, the state of Louisiana is contributing $1.7 billion, consisting of $0.2 billion for real estate acquisition and $1.5 billion for the state's cash-share contribution, for its share of the $5.0 billion in improvements funded through supplemental appropriations to the Corps Construction account. Under a specially negotiated arrangement, Louisiana's cash contribution initially was provided through federal appropriations and is being repaid over 30 years. Hurricane Katrina significantly damaged the Mississippi coast. In contrast to the congressional response to fund hurricane-protection construction through supplemental appropriations for Southeast Louisiana, Congress directed the Corps to develop a plan for how to protect coastal Mississippi.