**1. Introduction**

Finely textured sediments originating from upland areas get deposited further down in lowland areas, forming one of the most fundamental earth processes. Sedimentation processes stretch across other disciplines, including soil and plant science, geomorphology, and coastal zone management. Ongoing research in the field of sedimentology is, therefore, very relevant because changes in global sediment transport are being used as a primary form of evidence for the Anthropocene.

Like sedimentation, soil erosion is a dynamic, multistage process involving soil detachment, breakdown, transport, and subsequent deposition that is forced by wind or rain, or through soil-intensive human activities such as farming [1]. Soil erosion can lead to serious loss of topsoil and organic matter, which can lead to reduced vegetation growth and to biodiversity in general [2]. The focus of this chapter is on the multidisciplinary understanding between soil erosion, transport, and its impact within a localized watershed situated in the Maltese islands, using a range of techniques that are highly suited for risk management.

#### **Figure 1.**

*The Maltese islands show the study area located in Gozo. (Source: OSM & Malta GeoPortal – Planning Authority).*

The Maltese islands are located within the central Mediterranean region (**Figure 1**). According to CMIP6 climate models, the projected future climate of the islands is expected to experience a higher frequency of climatic extremes, including prolonged drought conditions and heatwaves, as well as increased frequency of torrential rain that can cause intermittent but significant flooding. The latter may, thus, result in increased mass wasting and related soil erosion, which can negatively affect erosion-vulnerable watersheds that are already significantly impacted by unsustainable and intense anthropogenic influences, including agriculture and associated sediment displacement. Clays and silts from upper parts of watersheds, once suspended in the stream network, can be routed directly to the mouth of the valley, resulting in significant sediment loads in coastal waters, and thus affecting exposed and submerged coastal ecosystems.

Severe rainstorms can have significant short- to long-term impacts on coastal water quality as a result of soil erosion and sedimentation processes both during and after their occurrence, especially if they are well outside historically observed norms. Extreme rainfall events can transport significant amounts of suspended sediment containing a variety of pollutants (such as heavy metals and organic compounds) through watersheds, ending up into coastal waters. Water runoff may also carry sufficiently coarse sediments to block the penetration of light through the water column, and thus be able to impact sensitive benthic flora and fauna. According to Ref. [3], the upper tolerance of total suspended sediments for most aquatic species is 80–100 mg/L, but it can be much less for bottom-dwelling aquatic invertebrates.

For these reasons, it is very important to understand the degree of these processes for eventual management of such risks within important watersheds. Such a study requires an accurate identification of the connectivity between the degree of soil erodibility and the corresponding impact to coastal waters resulting from sedimentation at the local scale. In this chapter, we look at an integrated assessment of sediment dynamics typically triggered by a rainstorm occurring within an important watershed in the Maltese islands, namely the identification of problems having a significantly high degree of soil erodibility, and the estimation of both total suspended matter (TSM)

and chlorophyll-a (CHLA). The morphometrics of the Ramla watershed was derived from a very high-resolution DEM derived using LiDAR, and evaluated in detail. The revised universal soil loss equation (RUSLE) model was used to assess the degree of soil erodibility, while Earth observation technology was used to estimate the impact of surface runoff on coastal water.
