This series of manuals on Techniques and Methods (TM) describes approved scientific and datacollection procedures and standard methods for planning and executing studies and laboratory analyses. The material is grouped under major subject headings called "books" and further subdivided into sections and chapters. Section A of book 3 is on surface-water techniques. The unit of publication, the chapter, is limited to a narrow field of subject matter. These publications are subject to revision because of experience in use or because of advancement in knowledge, techniques, or equipment, and this format permits flexibility in revision and publication as the need arises. Chapter A24 of book 3 (TM 3-A24) deals with proper identification, evaluation, and temporary preservation of perishable high-water marks for data collection and use as discussed in many of the other chapters in this section. In addition, an appendix introduces the identification of persistent paleoflood evidence left by historical floods.