Controls on sediment delivery in coastal plain rivers.

Area of Science:

• Geomorphology
• Sedimentology
• Hydrology

Background:

• Rivers crossing coastal plains often exhibit inefficient sediment transport, obscuring upstream dynamics at the river mouth.
• Extensive alluvial storage upstream of estuaries is common due to high accommodation space and low stream power, leading to reduced sediment loads reaching the coast.

Purpose of the Study:

• To investigate the factors controlling alluvial sediment storage and sediment yield in rivers crossing coastal plains.
• To highlight the limitations of traditional sediment gaging station data in representing coastal sediment dynamics.

Main Methods:

• Analysis of sediment records from gaging stations located upstream of coastal plains.
• Examination of alluvial sediment storage dynamics, focusing on factors beyond accommodation space.
• Case studies from Texas rivers to illustrate key geomorphic principles.

Main Results:

• Gaging stations upstream of coastal plains often overestimate sediment yields by under-representing lower coastal plain processes.
• Low transport capacity, primarily dictated by river slope, is a critical factor in alluvial sediment storage.
• Sediment dynamics at the river mouth are not always reflective of upstream changes due to inefficient transport and storage.

Conclusions:

• River slope and associated low transport capacity are crucial determinants of alluvial sediment storage on coastal plains.
• Understanding these factors is essential for accurately assessing sediment yields and river mouth dynamics.
• Coastal plain geomorphology significantly influences how rivers deliver sediment to the marine environment.