Spain's Coastal and River Depression Relief

The Ebro and Guadalquivir River Depressions

The Ebro Depression

The Ebro Depression is wedged between the foothills of the Pyrenees, the Iberian System, and the Catalan Coastal Range. It has a length of 380 km and a maximum width of 150 km. The Ebro River runs through this depression. The river and its tributaries form a communication network, where cities and irrigated areas are located. The Ebro flows through a passage between the Catalan Coastal Range that leads to the Mediterranean, where it forms a very extensive delta.

The Guadalquivir Depression

The Guadalquivir Depression is bordered by the Sierra Morena and the rugged Cordillera mountain ranges. This large, flat, triangular-shaped depression is about 330 km long and 200 km wide at the coast. It gradually slopes towards the west. Its altitude ranges between 150-200 meters. The depression is crossed by the Guadalquivir River, which passes near the Sierra Morena. This is an area where converted wetlands are currently a fertile rice-growing region. Around the wetlands, there is a wide strip of dunes formed by winds of Atlantic origin.

The Relief of the Spanish Coastline

Compared to other Mediterranean peninsulas like Greece and Italy, the mainland coast of Spain is generally open and has a relatively smooth outline, except for the Galician coast.

The Atlantic Coast

The Cantabrian Coast

High and straight landforms predominate. The beaches and coastal plains are low-lying. Cliffs form where the slopes of the mountains reach the coast, and tidal waves weaken the cliff base. When the rock is hard, the sheer cliff face retreats. When the rocks have varying hardness, erosion affects the less resistant parts, forming caves and recesses. Sometimes, *rasas* (flat surfaces bounded by stepped marine cliffs) are formed on the coasts. The Cantabrian estuaries are generally short and narrow, resulting from the erosion of river valleys.

The Galician Coast

The Galician coast stretches from the tip of Cape Ortegal to the border with Portugal. The most characteristic feature of the Galician coast is the *rias* (estuaries). The *rias* are ancient river valleys now flooded by seawater due to the subsidence of the coast or rising sea levels. The *rias* can penetrate up to 35 km inland. Depending on their location, they are classified as *Rías Altas* (Upper Rias) and *Rías Baixas* (Lower Rias).

The Andalusian Atlantic Coast

The Gulf of Cadiz extends between the Portuguese border and the Rock of Gibraltar. Rivers have built coastal plains with alluvium, resulting in low-lying coasts with sandy beaches and dunes, particularly on the coasts of Huelva and Cadiz. Ocean currents can accumulate sand in certain places, forming *flechas litorales* (coastal spits composed of rocky material resting on a dune, extending from the coast or an island). If these spits are arranged parallel to the coast, they form a coastal barrier.

The Mediterranean Coasts

The Mediterranean coast is formed by a series of low-lying coasts that tend to be straight, forming wide arches separated by rocky headlands such as Cape de la Nao, Cape Palos, and Cape Gata. Small coves, beaches, lagoons, and tombolos characterize the Mediterranean coast.

Three parts can be distinguished in the Mediterranean:

• Catalan Coast: It is not uniform but offers different reliefs: deltas, small coastal plains, rugged coastlines, and cliffs. The coastal mountain range reaches the sea, forming cliffs with small bays that make up the characteristic landscape of the Costa Brava.
• The Gulf of Valencia: It extends from Cape de la Nao to the Ebro Delta. It is a coastal plain about 400 km long, featuring beaches, marshes, lagoons, and tombolos.
• The Mediterranean Coast of Murcia and Andalusia: It stretches from the Strait of Gibraltar to Cape de la Nao. It is characterized by a coast carved by the reliefs of the Cordillera mountain ranges, with some areas of dunes and lagoons, such as the Mar Menor in Murcia.