Editing Stream bed (section)

== Climate change ==
The intensity and frequency of both drought and rain events are expected to increase with climate change.<ref>{{Cite journal |last1=Blöschl |first1=Günter |last2=Hall |first2=Julia |last3=Viglione |first3=Alberto |last4=Perdigão |first4=Rui A. P. |last5=Parajka |first5=Juraj |last6=Merz |first6=Bruno |last7=Lun |first7=David |last8=Arheimer |first8=Berit |last9=Aronica |first9=Giuseppe T. |last10=Bilibashi |first10=Ardian |last11=Boháč |first11=Miloň |last12=Bonacci |first12=Ognjen |last13=Borga |first13=Marco |last14=Čanjevac |first14=Ivan |last15=Castellarin |first15=Attilio |date=2019 |title=Changing climate both increases and decreases European river floods |url=https://www.nature.com/articles/s41586-019-1495-6 |journal=Nature |language=en |volume=573 |issue=7772 |pages=108–111 |doi=10.1038/s41586-019-1495-6 |pmid=31462777 |bibcode=2019Natur.573..108B |issn=1476-4687|hdl=11585/740407 |hdl-access=free }}</ref><ref>{{Cite journal |last1=Marsooli |first1=Reza |last2=Lin |first2=Ning |last3=Emanuel |first3=Kerry |last4=Feng |first4=Kairui |date=2019-08-22 |title=Climate change exacerbates hurricane flood hazards along US Atlantic and Gulf Coasts in spatially varying patterns |journal=Nature Communications |language=en |volume=10 |issue=1 |pages=3785 |doi=10.1038/s41467-019-11755-z |issn=2041-1723 |pmc=6706450 |pmid=31439853|bibcode=2019NatCo..10.3785M }}</ref> [[Flood]]s, or [[flood stage]], occur when a stream overflows its banks. In undisturbed natural areas, flood water would be able to spread out within a [[floodplain]] and vegetation of either [[grassland]] or [[forest]], would slow and absorb peak flows. In such areas, streambeds should remain more stable and exhibit minimal scour. They should retain rich organic matter and, therefore continue to support a rich biota ([[river ecosystem]]). The majority of sediment washed out in higher flows is "near-threshold" sediment that has been deposited during normal flow and only needs a slightly higher flow to become mobile again. This shows that the streambed is left mostly unchanged in size and shape over time.<ref name="Phillips&Jerolmack20162">{{cite journal |last1=Phillips |first1=Colin B. |last2=Jerolmack |first2=Douglas J. |year=2016 |title=Self-organization of river channels as a critical filter on climate signals |journal=Science |volume=352 |issue=6286 |pages=694–697 |bibcode=2016Sci...352..694P |doi=10.1126/science.aad3348 |pmid=27151865 |doi-access=free}}</ref>
In urban and suburban areas with little natural vegetation, high levels of [[impervious surface]], and no floodplain, unnaturally high levels of [[surface runoff]] can occur. This causes an increase in flooding and watershed erosion which can lead to thinner soils upslope. Streambeds can exhibit a greater amount of scour, often down to bedrock, and banks may be undercut causing [[bank erosion]]. This increased bank erosion widens the stream and can lead to an increased sediment load downstream.<ref>{{Cite web |last=US EPA |first=ORD |date=2015-12-23 |title=Urbanization - Stormwater Runoff |url=https://www.epa.gov/caddis-vol2/urbanization-stormwater-runoff |access-date=2023-06-08 |website=www.epa.gov |language=en}}</ref>