**2.1. Lakeshore in Lagoa de Mangueira**

stage can be seen with the alternate development of cuspate forelands. Regarding these phenomena, the division and reduction of the fetch distance owing to the formation of a large shoreline protrusion associated with shoreline instability under high-wave-angle conditions and the resulting change in the wave field are key factors. Ashton et al. [4] predicted that the forelands formed along the shoreline connect with each other, resulting in the segmentation of the water body into smaller rounded lakes. Uda et al. [5] predicted the three-dimensional (3-D) segmentation of a shallow rectangular water body using the BG model (a model for predicting 3-D beach changes based on Bagnold's concept) [6]. Uda et al. studied the emergence and mergence of small lakes and their segmentation using the same model [7], assuming that the wind blew from all directions between 0 and 360° with the same probability of occurrence and intensity, that is, a circular distribution of the probability. The segmentation into elliptic shapes, as shown in **Figure 1**, was not predicted in their study. It may be accomplished, assuming that the probability of occurrence of the wind direction is given by an elliptic distribution, similarly to the case of oriented lakes [8]. In this study, the segmentation of a rectangular water body was predicted, given a circular or elliptic distribution of the probability of occurrence of the wind direction.

**Figure 1.** Example of segmentation of slender water body: Lagoons facing Chukchi Sea [3, 4].

50 Applications in Water Systems Management and Modeling

In the coastal area, the segmentation of a shallow water body with a triangular or crescent shape can also be observed. To study the mechanism of segmentation of such a water body, several examples of segmentation together with the development of sand spits along the lakeshore were examined in Lagoa de Mangueira in Brazil, Lake Saroma and Lake Kitaura in

**Figure 2.** Enlarged satellite image of rectangular area in **Figure 1**.

**Figure 3** shows an example of segmentation and the development of sand spits along the lakeshore of Lagoa de Mangueira (location: 33°09′59"S, 52°49′32"W) in Brazil [7]. The crescent lake is 100 km long and 10 km wide at the center of the lake. Many cuspate forelands have developed along the lakeshore and, in particular, the intervals of the cuspate forelands formed on the west shore become short near the south end of the lake. On the other hand, sand spits with similar shapes and cuspate forelands have developed along the east and west shores, respectively, in the north part of the lake. This is a typical example of segmentation and the development of sand spits in a crescent lake.
