Rapid urbanization is driving changes to land use and land cover in the SWD region. As more and more rural areas are transformed into urban environments, (farmland and pastures to housing, roads, and parking lots) the nature of how water reacts to these new hardened surfaces changes natural hydrology with broad implications.
Simply put - concrete and asphalt don't absorb water. These impervious surfaces create more runoff that impacts flood discharge, water quality, and local water balance. Multiple studies have shown that increased urbanization changes how water drains as well as how quickly it is absorbed back into the earth. With more and more of the earth covered in hard surfaces that can't absorb water, communities have to spend more time working on drainage. The drainage must be managed as water is channeled from urban areas to natural streams, wetlands, and other water sources. This controlled urban runoff also often carries pollutants and debris from the towns and cities they run through. These pollutants impact water quality as they are channeled into lakes that are community water sources, and the debris can block or fill urban water management controls creating flood hazards. As extreme weather is figured into the equation, all of these issues are compounded.
Several locations within the SWD footprint are seeing the effects of rapid urbanization. The Texas Gulf Coast is experiencing unique and substantial land cover changes in the form of coastal erosion driving the retreat of the coastline. Rates of beach erosion of up to nearly 10 feet per year are largely driven by storm surge and high tides combined with sea level rise. The consequent impacts to water quality and water depth are accelerating the disappearance of wetlands, marshes, barrier islands, and other coastal habitats, all of which can play a crucial role in protecting coastal areas against storm surge.
Many habitats in the region are sensitive to and directly impacted by increased variability in extreme weather; shifting food, energy, and water dynamics; and changing landscapes driven largely by urbanization. Drought and temperature change also increase water temperatures, which places strain on aquatic habitats, especially in coastal bay waters, causing hypoxia and algal blooms.
All of these ecosystems are impacted by the risk drivers in different ways that often feed into one another. The continued integrity and stability of these ecosystems is important to the civil works mission areas in multiple ways. One of the most important is how it affects threatened and endangered species. More than just the plant and animals that are threatened there is the greater ecosystems that support them. Biodiverse coastal and freshwater ecosystems play a vital role in maintaining good water quality and naturally managing pollutants.
Leveraging our understanding of how all of these diverse parts integrate together and affect all Americans is of crucial importance to the civil works mission of the Corps of Engineers. CWSP and IWRM are tools we will use to ensure that USACE, its partners, and the citizens our civil works benefit are able to work together to create comprehensive civil works solutions that work today and tomorrow.