Dredging soil and rock classification is a fundamental step in the planning, design, and execution of marine and fluvial excavation works. The objective is to identify and categorize the seabed or riverbed materials so that appropriate equipment, production rates, costs, and environmental measures can be determined with confidence.In practice, classification begins with site investigation. This typically includes hydrographic surveys to define seabed levels, followed by geotechnical investigations such as boreholes, cone penetration tests (CPT), grab samples, and vibrocores. Laboratory testing is then carried out to determine grain size distribution, Atterberg limits, density, shear strength, and other relevant properties. Based on these results, materials are grouped into broad categories such as soft soil, granular soil, weak rock, and hard rock.Soft soils include clays, silts, and organic deposits with low shear strength and high compressibility. These are generally easy to dredge using cutter suction dredgers, trailing suction hopper dredgers, or backhoe dredgers. The main challenges with soft soils are slope stability, excessive turbidity, and the management of large volumes of fine sediments during transport and placement.Granular soils comprise sands and gravels, which are usually non-cohesive and exhibit good drainage characteristics. Sands are commonly targeted for land reclamation because they can be compacted to achieve stable foundations. Granular materials are efficiently removed and transported hydraulically using suction dredgers, and production rates are normally high. However, the risk of erosion and sediment dispersion must be carefully controlled.Weak rock represents an intermediate class that includes very dense sands, cemented soils, weathered rock, and soft sedimentary formations such as weak sandstone or marl. These materials may require mechanical cutting or limited blasting to achieve economical production. Equipment selection often includes cutter suction dredgers with more powerful cutter heads, backhoe dredgers with heavy-duty buckets, or grab dredgers with reinforced grabs.Hard rock consists of unweathered or slightly weathered rock formations such as competent limestone, basalt, granite, or other igneous and metamorphic rocks. Hard rock dredging typically demands specialized techniques, including pre-treatment by drilling and blasting, use of heavy backhoe dredgers with rock buckets, or cutter suction dredgers with rock cutters. Production is significantly lower and costs are higher than for soils, so accurate classification is essential to avoid contractual and technical disputes.Standards and guidelines are often used to formalize dredging soil and rock classification. These may rely on parameters such as unconfined compressive strength, point load index, or standard penetration test (SPT) N-values to distinguish soil from rock and to subdivide rock into strength classes. The resulting classification underpins decisions on contract conditions, risk allocation, equipment mobilization, and scheduling.Ultimately, dredging soil and rock classification links geotechnical properties to practical dredging behavior. A thorough and accurate classification enhances safety, reduces uncertainties in cost and time, and supports the sustainable management of marine and riverine environments during and after dredging operations.