Gravel deposits can be found using various geophysical and geological methods. Here are some of the most common methods used:
Geological Mapping: Geologists can use surface geological mapping techniques to identify areas where there is a high likelihood of gravel deposits. They will look for areas where erosion has exposed the bedrock or other geological formations that are known to contain gravel.
Geophysical Surveys: Geophysical surveys, such as electrical resistivity tomography (ERT), Capacitive resistivity survey (CT), and ground-penetrating radar (GPR), can be used to locate gravel deposits by identifying subsurface changes in the electrical or magnetic properties of the earth. For example, gravel deposits can have different electrical properties than the surrounding rock or soil, which can be detected using ERT.
Test Drilling: Test drilling involves drilling small boreholes to collect samples of the subsurface geology. These samples can be analyzed in a laboratory to determine if there are gravel deposits present.
Aerial Photography and Remote Sensing: Aerial photography and remote sensing technologies such as LiDAR and satellite imagery can be used to identify areas where there are changes in elevation or surface features that are indicative of gravel deposits.
Stream Sediment Sampling: Gravel deposits are often found in or near riverbeds, so stream sediment sampling can be a useful method for identifying areas where there are significant amounts of gravel.
It's worth noting that none of these methods are foolproof, and a combination of techniques is often needed to identify gravel deposits accurately. The most appropriate method will depend on the specific geological conditions of the area being surveyed.