LITMIR.BIZ

Скачать книгу

channel. They are highly responsive and dynamic rivers that can change significantly following a flood event. Depositional features are often large and floodplain connectivity is characteristically high. Anastomosed Anastomosing channels are rare but can be found across upland, hilly, and lowland zones. They develop a multi‐thread channel network separated by stable islands, bars, and berms. Floodplain connectivity is often excellent and different channels are activated at different flow levels, spreading flow energy over a wide area, creating stable channel conditions. The dominant bed material is dependent on energy levels with gravels dominating in upland zones and fines prevalent. Wet woodland often develops across the floodplain further enhancing overall stability. Active single thread This type of channel is associated with hilly terrains and some upland zones. They generally flow over a relatively low‐to‐moderate gradient. Sediment loads are moderate and has a large fine component. Lateral movement is progressive linked to outer bank erosion and inner bank deposition. Typical bar features include point, mid channel, and lateral bars and riffles. Occasionally, over‐supply of bedload can lead to the development of a plane bed. Passive single thread These are generally found in lowland areas flowing over low gradients. Bed material is generally dominant by finer sediment (e.g. sands and silts), and gravel features are uncommon or poorly developed if present. These channels are often heavily modified restricting lateral movement.

Figure 2.5 Temperate river typology used in this volume.

Table 2.6 Typical in‐channel morphologic assemblages by river type.

	Channel type
Morphologic unit	BC	SPC	BCPR	PBR	B	W	A	PLR	POR	PRBR	IST
Bedrock cascade	U	R	R	R
Bedrock controlled rapid	U	R	R	R
Bedrock influenced pool	U	R	R	R
Hydraulically controlled rapid	C	C	C	C
Obstruction induced rapid	O	O	O	O
Coarse sediment pool	O	C	C	C
Waterfall	C	O	R	R
Plunge pool bar	O	C	O	O
Boulder cascade	C	C	U	U
Bedrock step	U	R	R	R
Boulder step	C	C	O	O
Bedrock pool	U	R	R	R	Скачать книгу В начало < 8 9 10 11 12 13 14 15 > В конец