Natural vs. Modified HabitatPrimary Headwater Habitat Streams

Headwater Habitat Evaluation Index

What qualifies as a Natural PHWH stream?

Characteristics:Characteristics: A Watercourse with:A Watercourse with:

A defined BED and BANKA defined BED and BANK Either continuous or periodic FLOWING waterEither continuous or periodic FLOWING water A drainage generally LESS than one square A drainage generally LESS than one square

mile mile Deepest pools < 40cmDeepest pools < 40cm Widely divergent communities based upon in Widely divergent communities based upon in

stream Biologystream Biology No No ChannelizationChannelization1

What do Natural PHWH streams do?

Major Downstream Exports:

1. Desirable Biomass1 (fish, plants, birds, mammals, sensitive species)

1. Low Sediment2 Delivery

2. Water Quality Suitable for ALL Uses

Un-impacted PHWH Stream

What qualifies as a Modified PHWH stream?

Characteristics: A Watercourse with:A Watercourse with:

A channelized or moved course Man-made ditches Silt infilling Erosion1

No flowing water A filled or buried bed Increased sunlight from vegetation

removal Chemical pollution

What do Modified PHWH streams do?

Major Downstream Exports

Nutrients & Undesirable Biomass (algae, detritivores1, tolerant2 species)

High Sediment Delivery

Degraded3 PHWH Stream

A Natural Primary Headwater Stream

PHWH (Class III)

A Modified Primary Headwater Stream

PHWH (Class I modified)

Natural over Modified PHWH(Upland Benefits)

Increases land value

Reduces erosion Reduces or prevent

flooding Increases wildlife

habitat Increases beauty

Natural over Modified PHWH(Downstream Benefits)

Reduces flooding & channel scour1 (energy)

Processes nutrients & sediment Protects downstream ecology & water

quality Protects drinking waters supplies

Consequences of Continued Degradation of PHWH Streams

-Increased degradation of larger streams

-Increased maintenance costs

-Decreased wildlife habitat

-Other consequences

Glossary

Biomass - the total living biological material in a given area or of a biological community or group - biomass is measured by weight, or by dry weight per given area (usually measured per square meter or square kilometer)Channelization - the process of reconstructing the natural course of a stream in order to make it flow into a restricted pathDegradation - The wearing down of the land by the erosive action of water, wind, or iceDetritivores - Animals that consume decomposing organic materials and in doing so contribute to decomposition and the recycling of nutrientsDry Weight - the weight of the material minus the weight of water in the material - dry weight is often calculated by drying material until it no longer loses weight due to evaporationEncroached - To advance beyond proper or former limits

Glossary - continued

Entrenched - Established firmly and securelyEroding - displacement of solids (soil, mud, rock and other particles) by the agents of ocean currents, wind, water, or ice by downward or down-slope movement in response to gravity or by living organisms (in the case of bioerosion)Scour - Debris flows and floods may also occur when strong rains on hill or mountain slopes cause extensive erosion and/or what is known as "channel scour"Sediments - the matter that settles to the bottom of a liquid - in streams the sediments are the suspended particles that settle out when flow stopsTolerant Species - species that are able to tolerate environmental conditions or physiological stress, showing the capacity for endurance