Resacas are former channels of the Rio Grande found in the southern half of Cameron County. There are two explanations for the origin of the word "resaca." The less likely holds that it is a contraction of Spanish rio seco ("dry river"). The other is that the word stems from the Spanish resacar ("to retake"), since the primary geological function of a resaca seems to be diversion and dissipation of floodwater from the river. Resacas are naturally cut off from the river, having no inlet or outlet. Before land development and water control in Cameron County, floodwater from the Rio Grande drained into resacas from surrounding terrain. Over the years portions of the resacas silted up and became bottomland, forming the remaining stretches of channel into a series of unconnected horseshoe bends. The channels themselves were either dry or contained stagnant ponds and marshes. Development of resacas as reservoirs and channels for irrigation water started in 1906, when Col. Samuel A. Robertson began construction of a canal to connect the Resaca de los Fresnos with a pumping station on the Rio Grande at Los Indios. Many resacas are now filled with water by pumping, among them Resaca de los Fresnos in San Benito, Resaca de los Cuates in the Los Fresnos-Bayview area, and Resaca de la Guerra, Resaca de la Palma, and Resaca del Rancho Viejo in the Brownsville-Rancho Viejo area. Some rural resacas remain dry except in rainy weather. The ownership and administration of resacas varies according to jurisdiction. Some are owned by irrigation districts, some by municipal water corporations or utility districts, and some by owners of adjacent land who provide easement to public corporations. In urban areas resacas have been landscaped as community or residential showplaces, while those in rural areas are often left as marshlands. They serve as habitats for waterfowl, beaver, nutria, various species of amphibians and reptiles, including alligators, and various species of fish. Resaca de la Palma was the scene of a battle between United States and Mexican troops on May 9, 1846, although the battlesite is now covered by urban development.