The Lower Rio Grande Valley (LRGV) is a transborder region that lies in the floodplain of the Rio Grande/Río Bravo River. The region, which covers four Texas counties and the northern portion of the Mexican State of Tamaulipas, is home to more than 900 colonias on the Texas side of the border. These informal, unincorporated settlements–which house more than 400,000 people–are characterized by substandard housing and a lack of civil infrastructure including sewers, paved roads, and potable water. Many of the colonias flood regularly. This proposal imagines a modular, transitional approach to designing housing and landscape in LRGV colonias. While typical modular housing projects are standardized, prefabricated, packed, shipped, and assembled onsite; the following proposal extends modular efficiencies to the entire site, incorporating landscape, flood control, and canal systems. The holistic, modular approach allows for the flexible growth and decline of the community over the course of one hundred years. Ultimately, the transitional, modular model challenges the adversarial environmental, social, and economic arrangements that exist in colonia developments, imagining a more sympathetic relationship between people, water, and land.